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FRCR Clinical Oncology Part 1 COPY > Tumour biology > Flashcards

Tumour biology Flashcards

1
Q

Name the purines and pyrimidines in DNA and who they pair with

A

Purines : adenine, guanine
Pyrimidine: cytosine, thymine

A = T (2 hydrogen bonds)
G 三 C (3 hydrogen bonds)

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2
Q

How is DNA packaged?

A

DNA is an acid with highly negative charge
DNA helix wraps around nucleosomes consisting of histones (highly +ve charge) -> forms chromatin fibre -> coiled and packaged into chromosomes

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3
Q

Name the bases in RNA?

A

Purines: adenine, guanine
Pyrimdine: cytosine, uracil

A = U (2 hydrogen bonds)
G 三 C (3 hydrogen bonds)

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4
Q

Name the difference types of RNA and their assoc RNA polymerases?

A

rRNA (ribosomal)- up to 5kb- structural - made by RNA Pol 1
mRNA (matrix) - 1-10kb- carry messages to encode proteins - made by RNA Pol II
tRNA (transfer)- 76-90bp (very small) - made by RNA pol III

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5
Q

What are exons and introns?

A

Exons: coding DNA
introns: non-coding DNA

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6
Q

Define anaplasia?

A

Lack of differentiation and loss of morphological characteristics. Cellular and nuclear pleomorphism (different sizes). Hyperchromatic nuclei. Loss of orientation/polarity.

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7
Q

What is dysplasia and CIS?

A

Dysplasia is disordered growth. Loss of cellular uniformity and architectural orientation, pleomorphism, increased mitotic figures.
CIS: full thickness dysplasia with BM intact

Both can progress to cancer

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8
Q

What is metaplasia?

A

Change of one cell type to another cell type- eg Barretts (squamous to columnar) - may be pre-malignant

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9
Q

What is hyperplasia?

A

Increase in number of cells in a tissue eg HRT and endometrium. May be pre-malignant

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10
Q

What are the basic steps of making a protein from DNA?

A

Transcription
Translation - involves all 3 types of RNA, occurs in a ribosome
Post-translational modifications

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11
Q

Describe the process of transcription? Where and how does it start?

A

Usually started at 5’ end of DNA - contains a nucleotide sequence that make up the promoter region.
TATA box - located near the start of transcription is one of the most important regulatory elements
TBP (tata box-binding protein) is a transcription factor crucial for the initiation

Reaches stop codon - 3 codons always indicates stop protein synthesis - UAA, UAG, UGA

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12
Q

What is a somatic vs germ line mutation?

A

Somatic mutation- occur in somatic cells and only affect the individual in which the mutation arises
Germ-line mutation- alter gametes and passed on to offspring

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13
Q

Name some types of point mutations?

A

Substitutions- transitions/transversions
Deletions
Insertions

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14
Q

Describe the two types of base pair substitutions?

A

Transitions: convert a purine to another purine

  • 4 types - A↔G, T↔C
  • most result in a synonymous substitution

Transversions: convert a purine to a pyrimidine and vice versa

  • 8 types
  • more likely to result in non-synonymous mutations

Can result in:
- Nonsynonymous/misense mutation - base pair substitution results in a different amino acid eg sickle cell

  • Nonsense mutation: base pair substitution results in stop codon (short protein)
  • Neutral non-synonymous mutation: base pair substituion results in substitution of an AA with similar chemical properties (does not affect function)
  • synonymous/silent mutation
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15
Q

What type of mutation does an insertion/deletion of a base cause?

A

Frameshift mutation: deletions or insertions non divisible by 3 result in translation of incorrect AAs/codons.

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16
Q

What is a misense mutation?

A

Change from one AA to another due to a base pair substitution.

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17
Q

What is a nonsense mutation?

A

Base pair substitution results in a stop codon

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18
Q

What is chromothripsis?

A

When a chromosome shatters and in an attempt to repair the damage many incorrect junctions occur. Can disrupt tumour suppressor genes and produce oncogenic fusion genes.
CAUSES CANCER

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19
Q

Which type of UV radiation causes the most cancer?

A

UVB

UVA - reaches most acellular dermis (wavelength og 320-380nm)
UVB- reaches epidermis (wavelength 290-320nm)
UVC- absorbed by ozone, rarely reaches skin

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20
Q

How does UV radiation cause cancer?

A

UVB

  • causes CYCLOBUTANE PYRIMIDINE DIMERS- cause a bend in DNA helix so DNA polymerase cannot read DNA template -> it preferentially incorporates an A reside so TT dimers often restored to TC/CC dimers -> result in transitions (TC -> TT, CC-> TT). PYRIMIDINE DIMERS UNIQUE TO SKIN CANCER
  • Also get 6,4 photoproducts- abasic site

UVA

  • indirectly damages DNA via free-radicals, water is fragmented generating ROS -> cause DNA damage
  • G-> T transversions characteristic
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21
Q

What is characteristic of UVB radiation damage?

A

Pyramidine dimers - 2 types

  • cyclobutane pyrimidine dimers (2/3)
  • 6,4 photoproducts (1/3)
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22
Q

What is the carcinogen in coal tar from cigarettes and how does it cause mutations?

A 
Polyaromatic hydrocarbons : Benzo (a)pyrene
PAHs metabolised (by CYP1A1 enzyme) -> forms ultimate carcinogen -> forms adducts with purine bases -> results in G-> T transversions.
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23
Q

What in nitrosamines and nitrosamines causes cancer?

A

Found in tobacco, preserved fish and meats during smoking

Principal carcinogenic product is alkylated O6 guanine derivatives

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24
Q

What are DNA mismatches?

A

DNA can base pair incorrectly leading to DNA structure distortion
Tautomeric shifts
Deamination
Loss of bases: depurination, depyrimidination

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25
Q

What is a tautomeric shift?

A

A tautomer is a structural isomer.

Thymine and guanine usually in keto forms (C=O) -> undergo spontanous isomerisation to enol form (C-OH) - means they can join to keto forms of T and G

Cytosine and adenine usually in amino forms (C-NH2) -> undergoes spontaneous isomerisation to imino form (C=NH) -> means they can join to amino forms of C and G

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26
Q

What is deamination

A

Type of mismatch: Loss of an amino group (from C, G or A) can happen spontaneously and result in conversion of bases.
Cytosine -> uracil
Adenine-> hypoxanthine
Guanine -> xanthine

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27
Q

Name the different types of DNA repair?

A 
Direct repair
Base exicision repair- most common
Nucleotide exicison repair
Mismatch repair
DSB repair
- HR
- NHEJ
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28
Q

What is direct DNA repair and name some examples of direct DNA repair?

A

Damage is recognised by a protein factor and directly chemically reversed

Bulky alkyl adducts

  • recognised by O6- alkylguanine DNA alkyltransferase (AGT/ MDMT), the damaged base is flipped out of the DNA helix- methyl moeity is transfered to AGT protein
  • AGT is a suicide enzyme- only does one round of demethylation and it is not regenerated.

Pyramidine dimer - NOT in placental mammals
- recognised by photolyase which absorbs blue light and breaks the cyclobutane ring

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29
Q

Describe the process of base excision repair.

A

Targets chemically altered bases (eg 8-oxoguanine- failure to remove this results in G->T transversion mutation)

Initiated by DNA gylcosylases (eg OGG1, MUTYH) - recognise and remove damage to leave an AP- apurinic/apyrimidinic site

  • Scaffold protein XRCC1
  • AP site cleaved by endonuclease
  • repair takes place
  • DNA polymerase replaces the nucleotide and ligase 3 and 1 fills the gap
  • Poly (ADP-ribose) polymerase- PARP- interacts with single strand breaks and synthesise poly (ADP-ribose) chain that signal to other DNA repair proteins and leads to modification of histones and relaxation of chromatin to increase accessibility
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30
Q

What is the role of PARP in DNA repair?

A

SSB
- Poly (ADP-ribose) polymerase- PARP- interacts with single strand breaks and synthesise poly (ADP-ribose) chain that signal to other DNA repair proteins and leads to modification of histones and relaxation of chromatin to increase accessibility

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31
Q

What types of damage is NER useful for repairing?

A

UV induced DNA damage
Specific to helix distorting lesions eg pyramidine dimers, bulky DNA adducts
Cisplatin

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32
Q

Describe NER?

A

Recognition of damaged site leaded to excision of a short ssDNA segment by ERCC1-XP F nuclease (usually 10-20 bases) containing damage
Lots of other XP proteins involved
DNA polymerase copies the undamaged strand and DNA ligase seals off the ends.
No loss of information
Two forms- differ in how they recognise the damage
- GG-NER- global genome
- TC-NER- transcription coupled repair- actively transcribed strand of DNA is repaired with greater efficacy

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33
Q

When does mismatch repair occur?

A

Corrects errors that arise spontaneously during DNA replication

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34
Q

What disease is caused by NER deficiencies?

A 
Xeroderma pigmentosum
Rare AR disorder
Extremely sensitive to UV light
No radiosensitvity
Skin cancer, keratitis, mental retardation, premature dementia
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35
Q

How does mismatch repair work?

A

hMSH2/3 or 2/6 (also called MutS) recognises distorted structure in DNA and induces formation of a complex which leads to incision in the NEWLY synthesised strand of DNA. Gap is filled by polymerase and sealed by ligase.

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36
Q

Which cancer syndrome is caused by mismatch repair deficiencies?

A

HNPCC

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37
Q

Describe the process of NHEJ?

A
  • DNA ends recognised by Ku 70/80 (XRCC6/5) proteins -> recruit DNA-PK catalytic subunit
  • DNA-PK is whole complex including the Ku proteins which holds ends together
  • recruits artemis protein
  • XRCC4 and ligase 4 rejoin ends
    If DNA ends compatible they can be directly ligated together but often processed (resected) then ligated back together.
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38
Q

What are the pros and cons and NHEJ?

A

Quick 2-4hrs

LOST DNA, MUTAGENIC

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39
Q

When in the cell cycle does NHEJ occur?

A

Can occur at any point.
Very important in G1 PHASE of cell cycle as HR doe not occur.
Non proliferating normal tissues with low mitotic rate eg brain, kidney cord sit in G1 phase so if you were to inhibit NHEJ then would get back late toxicity.

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40
Q

What has overriding control and orchestrates response to DSBs?

A

ATM

- phosphorylation of histone H2AX by ATM/DNA-PK causes recruitment of proteins to site of damage

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41
Q

Describe HR

A

MRN complex- made up of Rad50 and Mre11 complex binds to ends of DNA and uses endonuclease activity to create single strand 3’ ends
Rad52 binds to DNA termini
Rad51 binds to exposed ends- BRCA 1/2 aids in nuclear transport of Rad51 and Rad52 helps with binding of Rad 51 to exposed ends.
Rad51 helps to seach for homologous template
When homologue is found the 3’ end of ssDNA serves as a primer to initiate DNA synthesis.
Resolvases restore the junctions known as Holliday junctions.

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42
Q

What does the fanconi anaemia pathway do?

A

Repair inter- strand cross link which block replication forms
Assembly of FA complex which recruits nucleases.
Breaks DNA and lesion is bypassed by translesional synthesis and further repaired with NER
Gap in 2nd strand is a double strand break and is repaired by HR

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43
Q

What is the double hit hypothesis

A

One copy of a gene is inherited mutated (germ line) in all cells of the body. Later on a second copy gets randomly mutated (somatic) which pushes the cell towards oncogenic transformation

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44
Q

What is synthetic lethality?

A

Genetic concept that describes buffering effect genes have on each other functions. If one targets a synthetic lethality partner of mutated gene one will achieve selected cell death in only cancer.

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45
Q

Why are BRCA and PARP synthetically lethal?

A

PARP is a key mediator in BER
BRCA1/2 key mediator in HR
In BRCA mutant cell HR is dysfunctional so cells heavily rely on BER. Because BER is blocked the single strand breaks become DSBs and HR not working to toxic to cells.

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46
Q

What causes genetic instability?

A

Replication errors- eg mismatch repair
Replication problems- impeded progress
Damage to DNA
Mitotic errors - chromosome segregation defects eg spindle assembly checkpoints.

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47
Q

What is a transcription factor?

A

Protein that binds to gene promoters and regulates transcription
3000 transcription factors regulate 20,000 genes

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48
Q

What is the structure of a transcription factor?

A

Contain a DNA binding domain, transcriptional activation domain, dimerisation domain and ligand binding domain.

4 types of DNA binding domains:
- helix-turn-helix motif
- Leucine- zipper motif
- helix- loop-helix motif
- Zinc finger motif
These domains are characteristic protein formations that enable transcription factor to bind to DNA
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49
Q

How is the activity of a transcription factor regulated?

A

Synthesis in particular cell types only
Covalent modifications eg phosphorylation
ligand binding
Dimerisation

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50
Q

Give some examples of transcription factors?

A

AP-1 (jun and fos family, dimerise in different ways)
Myc family (Myc, max, mad, mxi)- dimerise in different ways
Steroid hormones
RAR - retinoic acid receptor
p53

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51
Q

What is AP-1 and how does it work?

A

Transcription factor.
AP1- binds to TPA response element or to cyclic AMP response element in the promoter of target genes

AP-1 is made up of two components and is produced by dimers from Jun & Fos family (Jun, Jun B, JunD, Fos, FRA1 etc) - contain leucine zipper dimerisation domain.
Jun B acts as a negative regulator

AP-1 activated by specific signals eg GF, ROS, radiation

AP-1 can transform a normal cell to malignant cell

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52
Q

How do steroid hormone receptors act as transcription factors?

A

Superfamily of steroid hormone receptors act as ligand-dependent transcription factors.
Nuclear receptor family (42 members) eg Androgen receptor, oestrogen receptor, glucocorticoid receptor
Contain a zinc finger DNA binding domain, ligand binding domain for specific steroid hormones and dimerisation domain.
Each domain specific for that hormone.
Steroid hormones pass through cell membrane and bind to intracellular receptor in cytoplasm or nucleus -> receptors move to nucleus and activate transcription through specific DNA response elements.

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53
Q

What is the retinoic acid receptor (RAR) and how does it work?

A

Transcription factor
RAR is located in nucleus and acts as a transcriptional repressor in absence of retinoic acid (derived from vit A)
It binds to RA response element (RARE) in target genes as a heterodimer with RXR.
Aberrant forms of RARs are characteristic in some forms of leukaemia

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54
Q

What can a somatic mutation upstream of TAL1 gene produce?

A

TAL1 (T cell Acute Leukaemia 1)- oncogene which codes for basic helix-loop-helix transcription factor -> create a super enhancer which upregulates expression -> loads of transcription factors.

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55
Q

What makes up chromatin, nucleosomes and histones

A

Chromatin : thread of DNA (60%), assoc RNA (5%), protein (35%)

Nucleosome: 147 base pairs of DNA wrapped 1.7 x around core histone proteins. Histone core is an octomer of histones

Histone: contains domains for histone-histone, histone-DNA interactions and NH2-terminal lysine rich & COOH rich terminal tail domains which can be modified eg methylated/phosphorylated.

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56
Q

What is epigenetics?

A

Heritable information that is encoded by modifications of genome/chromatin components (not a change in DNA sequence so NOT mutations)

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57
Q

What are the two most common types of epigenetic modification?

A

Histone modification
DNA methylation
Both can be acquired or inherited.

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58
Q

What types of histone modification are there?

A

Acetylation
Methylation
Phosphorylation
Ubquination

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59
Q

Describe histone acetylation?

A 
Alters chromatin structure and effects gene expression. 
Acts as a docking signal for recruitment/replusion of chromatin
Histone acetyltransferases (HATs) - add acetyl group - neutralises positive charge on lysine residues and relaxes chromatin folding  - transcriptional activators recruit HATs

Histone deacetylases (HDACs) - remove acetyl group.

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60
Q

Name some examples of histone acetylation causing cancer.

A

EP300 gene coses for p300 protein a HAT
P300 usually acts as a tumour suppressor. Mutated in epithelial cell tumours.

Chromosomal translocation produces PML-RAR (APML)- recruits HDAC to promoter region of RA target genes and represses the expression of genes -> blocks cell differentiation.

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61
Q

Where does DNA methylation occur on DNA?

A

Addition of methyl group to position 5 of cytosine

ONLY occurs at cytosine nucleotides which are situated 5’ to guanine (CpGs)

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62
Q

Where do you find the most CpGs?

A

CpG is unequally represented in genome- which may be due to 5-methylcytosine easily deaminating to thymine causing a C-> T transition.
CpG islands- clusters of CpG located in promoter region of genes.

Methylated cytosines are mainly found in repressed genes eg X chromosome, inactivated genes, imprinted genes -> methylation is a heritable signal and assoc with compact chromatin structure and maintains gene silencing

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63
Q

What are DNMTs and what types are there?

A

DNA methyltransferases - mediate the covalent addision of a methyl group from a methyl carrier.

Three DNMTs:

  • DNMT1- during DNA replication this methylates DNA if original strand was methylated- allows inheritance of methylation
  • DNMT3a, DNMT 3b- involved in de novo methylation
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64
Q

Overall do cancer cell have more or less methylation of DNA than normal cells?

A

20-60% less methylation
Global hypomethylation with hypermethylation of specific gene promoters
30% breast cancers ER negative due to hypermethylation
BRCA1 can be inactivated by methylation
MGMT, MLH1- commonly methylated.

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65
Q

How do you detect DNA methylation?

A

Sodium bisulfite treatment- converts unmethylated cytosine to uracil but deamination.
Then do methylation specific PCR
Change grading of GBM

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66
Q

What are microRNAs (miRNAs)

A

Small non-protein coding RNAs (18-25 nucleotides) regulate expression of mRNAs
Able to repress hundreds of gene targets post transcriptionally -> powerful regulators of growth, differentiation and apoptosis.

Repress gene targets binding to 3’UTR of their target mRNA blocks translation
Can be oncogenes or tumour suppressors

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67
Q

What are telomeres?

A

Protect ends of the chromosomes from digestion by nuclear enzymes and prevent induction of mechanisms of repair of DNA double strand breaks.
Composed of several thousand TTAGGG repeats bound by a protein complex called shelterin complex

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68
Q

What is the end replication problem?

A

DNA shortens by 100-200 DNA bases with each round of replication due to limits of DNA polymerases

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69
Q

What is telomerase?

A

A ribonucleoprotein containing human telomerase reverse transcriptase (hTERT) and human telomerase RNA (hTR) which maintains the telomere length eg stem cells.
hTERT uses hTR as a template to add new repeats to telomeric DNA
AGAINST CENTRAL DOGMA OF BIOLOGY as synthesising DNA from RNA

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70
Q

How does cancer affect telomeres?

A

90% cancer upregulates telomerase

  • melanoma and other cancers have found mutations in TERT promoter.
  • c-myc increases expression of hTERT gene.

Telomere shortening occurs in response to DNA breaks and oxidative damage so may act as a tumour suppressor limiting replicative potential

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71
Q

What are the 4 types of protein involved in the transcription of growth factor signal?

A

Growth factors
Growth factor receptors (many are TKIs)
Intracellular signal transducers
Nuclear transcription factors

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72
Q

Name some types of EGFRs and what is their general function?

A 
EGFR 
- ErbB1/HER1
- ErbB2/HER2
- ErbB3/HER3
ErbB4/HER4

Family of receptor tyrosine kinases - important for transduction of a signal from an EXTRACELLULAR growth factor through the cell where regulates gene expression

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73
Q

What is the structure of an EGFR

A

Extracellular ligand binding domain
Single transmembrane domain
Cytoplasmic protein tyrosine kinase domain (except HER2 does not bind a known ligand, just acts as a co-receptor and HER3 only has weak kinase activity)

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74
Q

How does the growth factor signal get inside the cell?

A

Binding of EGF to receptor
EGFR receptor dimerisation
Conformational change in the receptor causes autophosphorylation (one half of dimer phosphorylates other half due to kinase activation)
The phosphorylated tyrosine resiues create high affinity binding sites for Src homology 2 (SH2) domains.
SH2&3 domains mediate protein-protein interacction in pathways activated by TKs.
Proteins that contain SH2/3 domains = Grb2, ABL, SRC, PI3K
SH3 domains interact with SOS which recruits Ras

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75
Q

What is Ras and what is its function

A

Ras is a GTP binding protein.
When bound to GDP inactive. SOS releases Ras from GDP and it binds to GTP

Ras is loosely bound to inside of cell membrane

Causes activation of Raf (MAPKKK) and PI3K

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76
Q

What is Raf?

A

A serine/threonine kinase- MAPKKK
- Raf recruited to cell membrane and binds to RAS-GTP -> activates it -> signal transducer and carries the signal away from the cell membrane.

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77
Q

Describe the Ras-Raf Pathway?

A

GF - extracellular
EGFR - dimerisation and autophosphylation -> SH2/3 domains
RAS - GTP (liberated by SOS from GDP)
RAF (MAPKKK)
phosphorylates MEK (MAPKK)
Phosphorylates MAPK
MAPKs -> enter nucleus targets AP-1 transcription factors (made up of Jun and Fos family members) and Myc family transcription factors (myc, max, mad, Mxi) dimerise in different ways.

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78
Q

Describe the PI3-k pathway?

A

PI3K - a lipid kinase interacts directly with Ras.
PIP-3 recuits PDK-1 to cell membrane
Then AKT recuited and phosphorylated and activated by PDK-1.
Activated AKT takes signal from the membrane and is involved in anti-apoptotic signals by phosphorylating distant target proteins
- mTOR (serine/threonine kinase) - downstream target Akt which is involed in promoting anabolic programmes eg lipid/nucleotide synthesis.

Akt can also travel to nucleus to the nucleus where is can phosphorylate transcription factors like FOXO (forkhead box O!!!!!!!!)

INHIBITED BY PTEN via PIP3

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79
Q

What is Src?

A

Intracellular tyrosine kinase- plays role in proliferation, adhesion, invasion and motility
Src normally phosphorylated which blocks its SH2 and SH3 domain.
Src activated by tyrosine kinase receptors like EGFR - reveals its active domains

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80
Q

What is an oncogene?

A

Mutated genes whose protein product is produced in higher quantities or whose altered product has increased activity and therefore acts in a dominant manner and contributes to carcinogenesis.
Types
- retroviruses - rous sarcoma virus
- GFs
-GFR
- Intracellular signal tranduscers eg Ras, Raf
- Transcription factors

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81
Q

Give an example of growth factor as an oncogene

A 
Proto-oncogene = c-sis produces PDGF
Oncogene = v-sis causes unregulated growth via activation of PDGF pathway
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82
Q

Give an example of a growth factor receptor oncogene

A

Proto-oncogene- RET - TK receptor
Transduces signal to glial derived neurotrophic factor family ligands
- papillary thyroid cancer
MEN2A and MEN2B
Oncogenic activation can lead to constitutive activation by dimerisation or increased kinase activity

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83
Q

Name some intracellular transducers that can become oncogenes

A

RAS

  • 30% human cancers
  • loss of GTPase activity- usually required to return active RAS-GTP to RAS-GDP causing constiutive activation

B-RAF
- melanoma (V600E)- causes constitutive kinase activity and insensitivity to feedback

Genes that code for cytoplasmic TKs can become oncogenes:

  • SRC- colon cancer Tyr530 on Src cannot form its inactive form so always active
  • ABL (nuclear kinase)
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84
Q

Name some transcription factors that can become oncogenes?

A

AP-1

  • components of AP-1- jun and fos are encoded by protooncogenes c-jun, c-fos.
  • truncation at end of v-fos means it produces an mRNA with a longer half life.

C-myc
- chromosomal translocation of myc (chromosome 8) to a location that falls within regulation of strong promoter of imumunoglobulin genes (chromsome 14) increases expression of myc gene -> Burkitts lymphoma

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85
Q

What are the mechanisms of oncogenic activation

A
  1. Point mutations and deletions in coding regions
  2. Mutations in gene promoter region
  3. Chromsomal translocations + insertional mutagenesis
  4. Gene amplification eg erbB2
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86
Q

How long is the cell cycle?

A 
Average length 16hrs
15hrs interphase
1hr mitosis
Varies depending on cell type
Chromosomes can only be observed in mitosis due to condensation
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87
Q

When is a cell irreversibly committed to the cell cycle?

A

On passing G1 restriction point

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88
Q

Describe the order of the cell cycle

A 
G0 -> mitogens/GFs induce cells to re-enter cycle
G1  - CYclin D + cdk4/6
G1 checkpoint
S phase  Cyclin E + cdk2
                Cyclin A + cdk2
G2 phase  Cyclin B/A + cdk1
G2 checkpoint
Mitosis
M checkpoint
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89
Q

How do cyclin-cdk complexes exert their effect?

A

Upon binding cyclin induces a conformational change in the catalytic subunit of the cdk partner revealing its active site -> phosphorylate target proteins including transcriptional regulators, cytoskeleton proteins, nuclear pore, envelope proteins, histones.
Dephosphorylation is important for resetting the cycle.

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90
Q

Where does cyclin D act and how?

A

Drives progression through G1
Binds to cdk4/6
ONe of its final targets is EGF signalling pathway
Plays role in regulation of cyclin E

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91
Q

Where does cyclin E act and how?

A

Important for G1-S phase progression

Binds to cdk2

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92
Q

Where does cyclin A act and how?

A

Important for S phase progression

Binds to cdk2

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93
Q

Where does cyclin B/A act and how?

A

Directs G2 and G2->M phase

Binds to cdk1

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94
Q

What are cdks?

A

Serine/threonine kinases that regulate progression of the cell cycle via phosphorylation.

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95
Q

What are the mechanisms of cdk regulation

A
  • association with cyclins - activates cdk, cyclins degraded by proteasomes after being flagged by ubquitin
  • Association with cdk inhibitors - 2 families p16ink4a (INK) family and p21 (cip/kip) damily.
  • INK proteins bind cdks 4/6 and interfere with binding to cycle D
  • p21 family members interact with both cyclins and their assoc cdks and block ATP binding sites
  • addition of phosphate groups that activate or inactive cdk activity.
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96
Q

What is a key substrate of cyclin d - cdk4/6 complex?

A

Rb protein

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97
Q

How does Rb protein regulate the G1 checkpoint?

A

Rb protein is a key substrate of cyclin d-cdk4/6 substrate
Rb regulates activity of E2F transcription factor- crucial for expression of genes needed for S phase.

Hypophosphorylated Rb sequesters HDAC and E2F so transcription repressed.
Cyclin d-cdk4/6 causes partial phosphorylation of Rb and release of HDAC -> repression relieved for some genes like cyclin E
Additional phosphorylation by cyclin E- cdk2 causing release of E2F

This occurs in response to growth signals

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98
Q

What happens at the G2 checkpoint?

A

Blocks entry into M phase in cells that have incurred DNA damage - allowing repair
DNA damage activates either -> ATM or ATR -> phosphorylate and activate Chk 1 and Chk2
Chk 1 prevents cdks from becoming active
After sucessful repair- PLK1 which targets Chk1 for degradation and inhibits Chk2.

Topoisomerase II - relieves torsional stresses by making dsDNA breaks in order to detangle ready for anaphase.

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99
Q

Describe the steps in mitosis

A

Prophase- appearance of chromosomes as result of condensation, nuclear membrane breakdown, separation of duplicated centrosomes, assembly of mitotic checkpoint proteins at centromeres.

Metaphase- aliging chromosomes on metaphase plate and assembly of microtubules to form mitotic spindle

Anaphase- spindle pulling apart and separating chromatids

Telophase- accumulation of chromosomes at their respective poles, reforming nuclear membrane, chromosome decondensation and cytokinesis

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100
Q

What happens at the spindle assembly checkpoint/mitotic checkpoint?

A

Signalling cascade that ensures the correct chromosomal segregation during mitosis and production of two genetically identical nuclei

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101
Q

What does anaphase complex do?

A

An ubuiquitin–protein ligase that regulates mitosis
During metaphase unattached chromatid pairs recruit proteins that inhibit anaphase complex. Once chromatids attached to microtubules they stop inhibiting it.
Anaphase complex targets securin - once degraded protease separase is activated
Separase cleaves protein link between sister chromatids allowing them to separate

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102
Q

What are aurora kinases?

A

Aurora kinases A, B, C
Regulate important aspects of mitosis
Serine -threonine kinases that phosphorylate target proteins

Aurora kinase A: localises centrosomes during interphase & thought to play role in centrosome maturation
Aurora kinase B: activity highest later in mitosis- role in spindle attachment and chromosome segragation
Aurora kinaseC - active during late mitosis

Aurora kinases frequently overexpressed in cancers

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103
Q

What mutations in cdks are you aware of?

A

Miscoding mutation in cdk4 stops it binding to INK4 inhibitors in subset melanoma patients
Cdk4 required for development of mammary gland tumours
Overexpression of cdk6 in some leukaemias

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104
Q

Name some tumour suppressor genes?

A

BRCA1/2
PTEN
Rb
p53

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105
Q

What is a tumour suppressor gene?

A

Hereditary syndromes that cause cancer predispositions

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106
Q

What is the role of BRCA1?

A

Recruitment of Rad51 to DSBs - HR

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107
Q

What is the role of BRCA2?

A

More diverse role in HR and regulation of transcription

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108
Q

What is PTEN?

A

Gene encoding a phosphatase with dual specificity. It can act as a protein and lipid phosphatase.
PTEN -> dephosphorylates the membrane lipid PIP3 -> PIP2
PIP2 inhibits the PI3K pathway

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109
Q

How does PTEN mutation cause cancer?

A

Loss of inhibitory dephosphorylation activity of PTEN (for PIP3) can result in a consituitively active PI3K pathway.

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110
Q

What syndromes does a germline mutation of PTEN cause?

A

Cowden disease

- harmartomas, risk of breast, endometrial and thyroid tumours

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111
Q

Describe the differences in the sporadic and familial form of retinoblastoma

A

Familial (40% cases)

  • one germline mutation and second sporadic- often results from somatic mitotic recombination in which normal gene is replaced with the mutant copy
  • often bilateral

Sporadic form (60% cases)

  • both mutations occur somatically in the same retinoblast.
  • low chance of this occuring > once so usually only affects one eye
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112
Q

What is Rb?

A

Transcriptional co-factor that can bind to transcription factors and either inhibit or induce transcription factor activity
Rb has >100 known protein binding partners
Main role is to regulate G1 -> S phase transition
Facilitates activity of E2F and chromatin remodelling enzymes
Cell cycle arrest can be induced by Rb via stabilisation of CDK inhibitor p27.

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113
Q

What are the upstream activators of p53?

A

DNA damage
Aberrant growth signals
Cell stress- radiation, drug, hypoxia, nucleotide depletion

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114
Q

What are the downstream responses possible when p53 is activated?

A

Cell cycle arrest or senescence
DNA repair
Apoptosis
Inhibition of angiogenesis

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115
Q

What is the structure of p53 protein

A

p53 - phosphoprotein transcription factor containing 4 distinct domains:

  • Amino-terminal transactivation domain and MDM2 binding site
  • DNA binding domain containing Zn ion
  • Tetramerisation domain
  • carboxy-terminal regulatory domain

-p53 binds as a tetramer to p53 response element

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116
Q

How is p53 regulated?

A

Regulated at level of protein degradation not gene expression
Main regulator = MDM2

Other regulators: MDMX and HAUSP (removes Ubiquitin form p53)

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117
Q

What is MDM2?

A 
Main regulator of p53 protein
Ubiquitin ligase (flags protein for proteolysis)
Modifies the carboxy-terminal domain of p53 tagging it for degradation. 
It also binds and inhibits p53 transactivation domain and transports protein into cytoplasm away from nucleus
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118
Q

How is MDM2 regulated?

A

p53 stimulates production of MDM2

Low amounts of p53 will reduce transcription of MDM2

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119
Q

What is the activation pathway (upstream of p53) when a DSB occurs?

A

DSB -> stimulates ATM -> phosphorylates and activates Chk2 -> ATM + Chk2 phophorylate amino-terminal sites of p53 -> interferes with binding of MDM2

120
Q

What is the activation pathway (upstream of p53) when cellular stress occurs?

A

Cell stress -> activates ATR -> casein kinase II -> phosphorylates p53

121
Q

What is the activation pathway (upstream of p53) for oncogene activation?

A

Activated oncogenes eg Ras -> activity of protein p14arf -> sequesters MDM2 to nucleolus of nucleus

122
Q

What are the downstream activators once p53 has been activated?

A

INHIBITION OF CELL CYCLE
Transcriptional induction of p21 gene -> product p21 inhibits several cyclin-cdk complexes and causes pause in G1->2 transition

APOPTOSIS

  • several mediators of apoptosis transcriptionally regulated by p53
  • induces pro-apoptotic proteins NOXA, PUMA, p53AIP1
  • tips balance regulated by Bcl-2 towards apoptosis

DNA repair and angiogenesis

  • Gene XPC is involved in nucleoside excision repair and is regulated by p53
  • Thrombospondin an inhibitor of angiogenesis is also regulated by p53
  • Induction of miRNAs is important for inhibiting stem call and preventing mets
123
Q

How does p53 decide which of the downstream outcomes occur?

A

Phosphorylation of Ser46 results in preference for apoptosis

Absolute levels of p53 and transcription factors affect response

124
Q

What binds to p21 and regulates it?

A

p53 and MIZ 1 bind to promoter and induce transcription resulting in cell cycle inhibition

However if myc is present it competes with p53 and binds to p21 and inhibits transcription blocking cell cycle inhibition

125
Q

What is the most common type of mutation in p53? How does this compare to other tumour suppressor genes?

A

> 75% p53 mutations = missense mutations - most of these are located in the DNA binding domain

Differs from classical tumour suppression genes -> tend to have nonsense or frameshift mutations that lead to inactivated truncated proteins.

126
Q

What is Li-Fraumeni and how is it inherited?

A

Germline mutation of p53
AD disease
25 x increase risk of developing cancer <50yrs
Sarcomas, breast cancer, leukaemia, brain tumours

127
Q

Patients with Li-fraumeni syndrome do not usually lose other p53 gene, remain heterozygous. This does not fit with Knudsons hypothesis. Why might this be?

A

Reduced amounts of p53 (haploinsufficiency) can cause transformation, also specific mutations may result in varied amounts of tumour suppressor.
Some p53 do not lead to loss of function but instead form altered protein that interacts with the normal p53 and inactivates it.

128
Q

What is the continuum model of tumour suppression?

A

Integrates the two hit hypothesis with broader concept
Subtle dosage effects of tumour suppressor either as changes in level of expression or protein activity
eg p53- one dominant negative mutation can cause tumour suppression

129
Q

What can viruses do to p53?

A

Adenovirus E1A, papillomavirus E6 & E7 etc inactivate Rb.

Some do this using uquitin-proteosome system to degrade it.

130
Q

How does HPV virus affect p53?

A

p53 is rarely mutated
binding of HPV protein E6 to p53 causes it to be flagged for degradation

Polymorphisms in p53 gene leads to differences in risk for cervical cancer. eg pts with 2 allelles coding for Arg have 7 x increased risk as it is more susceptible to degradation by HPV E6

131
Q

What is apoptosis?

A

Highly regulated process of programmed cell death, active process.

132
Q

WHat is necrosis

A

Sloppy process whereby cells swell, cell membranes become leaky and cells pill out contents into surrounding tissue and cause inflammation?

133
Q

What are caspases?

A

Specific proteases that act like molecular scissors to cleave intracellular proteins at aspartate residues

134
Q

Describe the extrinsic pathway of apoptosis?

A 
Death factor (eg Fas ligand/TNF) -> binds to transmembrane death receptors (Fas/TNF-r)
Receptors form homotrimers undergo conformational change and expose intracellular death domains.

Intracellular adaptor proteins (FADD/TRADD) transduce signal to caspases
Recruit pro-caspase 8 via death effector somains.
Pro-caspase 8 activate when close together by self cleavage
CASPASE 8 IS INITIATOR -> cascade of caspases -> executioner caspases (3,6,7)
Proteolysis of target proteins
(caspases also cleave Rb suggesting it may have a role in inhibiting apoptosis)

135
Q

What is the initiator caspase in extrinsic apoptosis?

A

Caspase 8

136
Q

What inhibits extrinisic apoptosis?

A

c-Flip

Binds to FADD or caspase 8 and inhibits caspase 8 recruitment and activation

137
Q

Describe the process of intrinsic apoptosis?

A

Stimuli inside the cell eg DNA damage
Induced via Bcl-2 family which act at outer mitochondrial membrane.
One group of Bcl proteins inhibit and one group promote apoptosis.
On activation of BH3 only proteins, Bid and bim activate Bax -> translocates to mitochondrial membrane -> oligomerises into the membrane -> causes membrane to become more permeable and release apoptotic mediators -> cytochrome c joins to Apaf-1 and recuits pro-caspase 9 -> activates -> caspase cascade
Smac/DIABLO released from mitochondria inhibit IAPs that normally block caspases.

138
Q

How do the anti-apoptotic proteins work in intrinsic apoptosis?

A

Cause dissociation of Bax oligomers from the mitochondrial membrane

139
Q

What are the pro apoptotic members of the Bcl family?

A

BH3- only, pro apoptotic

  • Bad
  • Bik
  • Bid
  • Bim
  • Noxa
  • Puma

Pro apoptotic other members

  • Bax
  • Bok
  • Bak
140
Q

What are the anti- apoptotic members of the Bcl family?

A 
Bcl-2
Bcl-w
A1
Boo
Mcl-1
Bind to and inhibit pro-apoptotic proteins
141
Q

What is the process of release of apoptotic mediators form mitochondrial membrane called?

A

MOMP

Mitochondrial Outer Membrane Permeabilisation

142
Q

How is the extrinsic and intrinsic pathway of apoptosis linked?

A 
Caspase 8 (extrinsic pathway) can cleave and activate Bid -> stimulate intrinsic pathway. 
ATM kinase phosphorylates Bid and is required to cause cell cycle arrest
143
Q

How is p53 involved in apoptosis?

A

p53 functions both in the nucleus and cytoplasm by transcription dependent and independent means.
FUNCTIONS LINKED TO PUMA
- p53 can repress expression of anti-apoptotic factors (Bcl-2, IAPs)
- PUMA (p53 upregulated modulator of apoptosis) - member of Bcl-2 family is essential for p53 induced apoptosis
p53 activates PUMA which acts as an enabler for release of Bcl-x from p53 so p53 can activate Bax

144
Q

Are cancer cells “closer” to apoptosis?

A

Yes
Contain more caspases but these inhibited by upregulated IAPs
TRAIL receptors (subfamily of TNF receptors) - ligand TRAIL induces apoptosis via caspase 8 in many cancer cells regardless of p53 and NOT in normal cells

145
Q

How can cancer alter the extrinsic pathway of apoptosis?

A

Sunburn/UV causes clustering of Fas death receptors and activation of caspase cascade (mutation in Fas-r may lead to increased risk of skin cancer)

Loss of caspase 8 in SCLC and neuroblastomas

146
Q

How can cancer alter the intrinsic pathway of apoptosis? How does this affect treatment?

A

More common than extrinsic pathway
Mutations in p53/MDM2/ATM/Chk2
Bcl-2 translocation t(14,18) - B cell lymphoma
Mutations in bax and bid (Bax >50% mutated in colorectal)
Apaf-1 (co-activator of caspase 9) mutated and repressed in mets melanoma
XIAP induced leukaemia, lung, prostate cancer (supress caspase 9/3/7)

MAKE CANCERS RESISTANT TO CHEMOTHERAPY
eg loss of bax makes resistant to 5FU in colorectal

147
Q

What are alternative death pathways that are caspase independent and what do they involve?

A

Use alternative proteases eg calpains, cathepsins, serine proteases
eg autophagy, mitotic catastrophe

148
Q

What are cancer stem cells?

A

Rare cells within a tumour that have the ability to self renew and give rise to phenotypically diverse cancer cells with limited replicative potential that make up the rest of the tumour
This self renewal provides an extended window for mutations.

149
Q

How is it proposed that the dergulation of self renewal of stem cells occurs in cancer?

A

Normal stem cells maintain a balance between self renewal and differentiation. Loss of balance can lead to unregulated self renewal.
Alternatively differentiated cells may acquire a mutation which reactivates self renewal programme

150
Q

What is wnt signalling pathway?

A

evolutionarily conserved cell-cell communication system that is important for stem cell renewal, cell proliferation and cell differentiation both during embryogenesis and during adult tissue homeostasis.
19 members of Wnt proteins - INTER cellular signalling molecules.
Lipid modficiations of Wnt by protein porcupine play a role in its secretion from cell.

151
Q

Describe the Wnt pathway when no Wnt ligand present?

A

In cytoplasm (intracellular)

  • Several proteins (APC, Axin, glycogen synthase kinase & casein kinase) aggregate together to form a degradation complex
  • complex targets β- catenin (a transcriptional co-activator) for degradation by phosphoylating and ubquintinating it.
  • In absence of β-catenin transcription is repressed by transcriptional repressor Groucho
152
Q

Describe the Wnt pathway when Wnt ligand is present?

A

Wnt (extracellular) binds to its transmembrane receptor (can be G protein coupled & TKRs) called Frizzled.
Frizzled co receptor LRP undergos change and its cytoplasmic tail is phosphorylated by GSK3 &CKI)
This allows β-catenin to escape from degradation complex and move to nucleus
Acts as a co-activator (with Bcl-9 & pygopus) of T cell factor/LEF family of transcription factors (eg c-myc, cyclin D)

153
Q

How can Wnt1 be affected by cancer?

A

Wnt1 is a proto-oncogene

Mutations constiutively activated Wnt pathway

154
Q

Which cancer is most likely to be caused by mutations in Wnt pathway?

A

Colorectal , >90%

Most mutations inactivate APC or activate β-catenin (rarely affect Wnt)

155
Q

What is FAP?

A

Familial adenomatous polyposis
APC gene acts as a tumour suppressor gene - if both copies inactivated -> cancer
Most mutations are truncating mutations of APC
Constitutive activation of Tcf transcription factors

156
Q

What is the role of the hedgehog signalling pathway?

A

Role in embryonic development, tissue self renewal and carcinogenesis
Cilia

157
Q

Describe hedgehog family and the transmembrane receptors with which they interact?

A

3 members Hh family: Sonic, Desert and Indian = INTERcellular signalling molecules

2 transmembrane receptors: patched and smoothened (related to Frizzled)- responsible for signal transduction by Hh- interaction regulated within cilia.

158
Q

Describe the hedgehog signalling pathway is absence of any hedgehogs?

A

Patched is localised in the cilia (at top) and inhibits smoothened (from coming to top of cilia)

Gli (zinc fingered transcription factor) - sequestered by a protein complex in cytoplasm which induces cleavage of Gli by proteosomes -> results in a repressor -> nucleus and inhibits transcription of Hh target genes

159
Q

Describe the hedgehog signalling pathway in presence of hedgehogs?

A

Sonic, desert or Indian bind to patched
Patched is translocated from cilia allowing smoothened to relocate there.
Smoothened tranduces a signal into cell - causes large protein complex to dissociate and release Gli
Gli moves to nucleus and regulates expression of Hh genes (VEGF, cyclin D, Bcl2, Snail)

160
Q

How is the hedgehog signalling pathway related to cancer?

A

Patched is a tumour suppressor gene

161
Q

What does a mutation in patched cause?

A

Gorlin syndrome- germline mutation in one copy of patched -> BCC, medulloblastoma, rhabdomyosarcomas

All sporadic BCCs
30% sporadic medulloblastomas

162
Q

What is organotropism?

A

Specific cancers metastasise to particular sites
Many can be explained by direction of blood flow
1/3 cannot0 > seed and soil

163
Q

What is pre-metastatic niche?

A

A site of future metastasis that is altered in preparation for arrival of tumour cells

164
Q

How do tumours spread?

A

Can be monoclonal (seeded by one cell)
Or polyclonal (seeded by two or more cells)
Can also be seeded from other metastases

165
Q

How do cells break free from normal molecular constraints in order to metastasise?

A

EMT- epithelial-mesenchymal transition

Conversion of closely connected epithelial cells into highly mobile mesenchymal cells.

166
Q

What is EMT characterised by?

A

Loss of cell polarity
Deconstruction of epithelial cell-cell junctions
Changes in cell shape
Downregulation of epithelial markers eg e-cadherin
Upregulation of mesenchymal proteins eg n-cadherin
Secretion of specific proteases
Increased cell protrusions and motility

167
Q

How is EMT induced?

A

Can be induced via a variety of transcription factors which can be activated via growth factors (eg HGF, EGF, PDGF, TGF), MAPK, PI3K pathway

ULtimately specific transcription factors eg Twist, snail, slug

168
Q

What anchors cells in place extracellularly and what is the their intracellular component?

A

CAMS and cadherins
Cadherins are calclium dependent transmembrane glycoproteins that have an extracellular hook and bind to other caherins on cell next to them.
They interact via their intracellular catenins.
Catenins can also bind transcription factors and induce gene expression in nucleus

169
Q

What is the predominant CAM in epithelial cells?

A

E-cadherin - secure cell-cell adhesion and suppresses metastasis.
Mutations of extracellular domain and methyltion in promoter region of E-cadherin gene have been identified in gastric/prostate cancer

170
Q

What are integrin receptors?

A

As well as breaking free from caherins. Cells must break free from normal molecular constraints by ECM
Integrin receptors are a family of >24 heterodimers made up of a range of alpha and beta subunits that mediate cell-ECM interactions.
They also help with some inside -> outside and outside -> inside signalling. Induce conformational change in the extracellular domain changing the affinity of integrins for their ECM ligands

171
Q

What is involved in the ECM?

A

ECM components eg collagen, fibronectin, laminin
Recognised by integrin receptors
Upon ligand binding the integrins clusster in the membrane and affect the cytoskeleton through interaction with actin-binding proteins and kinases like focal adhesion kiase(FAK)

172
Q

How are integrin receptors changed in cancer?

A

Altered expression of receptors observed in tumour cells during EMT

173
Q

What is the role of serine proteases and MMPs?

A

Invasion of tumour cells into surrounding tissue requires the action of specific proteases that degrade a path through the ECM and stroma
MMPs can cleave the extracellular domain of E-cadherin and so contribute to loss of epithelial cell-cell junctions.

174
Q

What regulates MMPs?

A

Carefully regulated as they are synthesised as latent enzymes requiring cleavage.
TIMPs regulate their function

Extracellular matrix metalloproteinase inducer (EMMPRIN) is upregulated on membrane of tumour cells and induces production of MMPs in adjacent stromal cells.

175
Q

Describe the process of intravasation of a tumour cells?

A
  1. Cell must attach to the stromal face of vessel
  2. Degrade basement membrane (using MMPs/serine proteases)
  3. Pass between endothelial cells (transendothelial migration) into the blood stream
176
Q

What helps to guide the tumour cells into the vessels? How do they do this?

A

Tumour associated macrophages
Involves colony-stimulating factor 1 (CSF 1) receptor on macrophages and EGFR on tumour cells.
Macrophage associate with blood vessels and produce EGF -> binds to EGFR on tumour cells -> tumour cells produce CSF 1 which interacts with macrophages and leads to chemotaxis-mediated co-migration.

177
Q

What are CTCs?

A

Tumour cells within the bloodstream

Can travel singly or in clumps together with platelets as emboli

178
Q

Describe the process of extravasation of a tumour cell?

A
  1. Tumour cell must attach to the endothelial side of the blood vessel
  2. Pass through the endothelial cells and basement membrane (transendothelial migration)
  3. Migrate into the surrounding stroma
179
Q

How do CTCs bind to the endothelium?

A

E- selectin is important
Binding to endothelium via e-selectin receptors on endothelium mediates adhesion and also triggers a signal cascade by activating stress-activated protein kinase 2 (SAPK2) - necessary for transendothelial migration.

180
Q

What are DTCs?

A

Disseminated tumour cells

cells that have spread but have not yet colonised.

181
Q

What is the pre-metastatic niche?

A

A site of future mets that is alerted as a result of factors released by primary tumour in preparation for the arrival of tumour cells.
Supports the seed and soil theory

182
Q

What are exosomes and how can they contribute to a pre-mestastatic niche?

A

Small vesicles that carry protein and nucleic acids which can travel in the circulation.
They can carry DNA, RNA and protein to cells to which they can fuse- called horizontal transfer -> role in promoting mets.
Can provide “education” to and change behaviour of receiving cells.

183
Q

What are metastatic suppressor genes?

A

Definited by ability to inhibit overt metastases without affecting growth of primary tumour
23 identified
- NM23
-MKK4
Both promote dormancy/apoptosis of micromets

184
Q

Name some pro angiogenic factors?

A

Non specific growth factors
- EGF, HGF, FGF, PDGF

Vascular endothelium specific growth factors

  • VEGF & VEGF-R - MAIN PLAYER
  • angiopoeitins
  • Tie receptors
185
Q

Describe the VEGF family?

A

5 members
VEGF-A-D and placental growth factor (PIGF)

3 VEGF tyrosine kinase receptors
- VEGFR -1, -2, -3

186
Q

What does VEGFR-1 do?

A

VEGFR-1 acts as a decoy by regulating the amount of VEGF-A available to VEGFR-2 as the binding affinity for VEGFR-1 is higher but its kinase activity lower so it restricts angiogenic response

187
Q

What does VEGF-C bind to and whats its role?

A

Binds to VEGFR-3 and plays a role in lymphatic systems

188
Q

Describe the signal transduction when VEGF-A is made.

A

VEGF-A produced by tumour cells and can be induced in surrounding normal cells.

  • Binds to two VEGFR-2 receptors -> dimerisation and phosphorylation.
  • intracellular proteins containing SH2 domains bind to phosphosphorylated receptor -> trigger
    • Ras-Raf-MAPK pathway - stimulated VEGF genes
    • PI3K pathway - AKT leads to inhibition of apoptosis and production of endothelial nitric oxide synthase (eNOS) that stimulates endothelial permeability

VEGF responsive genes include EGFR ligand, epiregulin, COX2, MMP1, MMP2

189
Q

Name some angiogenic inhibitors?

A 
Angiostatin
ENdostatin
Prolactin
P53
Thrombospondin-1, -2
190
Q

How is angiostatin produced and what is its role?

A

Plasminogen can be cleaved by proteinases including several MMPs to release angiostatin.
Angiostatin binds to endothelial cell surface receptor, annexin II to exert its inhibitory effects on angiogenesis

191
Q

How is endostatin produced and what is its role?

A

Fragment of collagen XVIII
Can be proteolytically released by elastase and cathepsin
Blocks MAPK activation in endothelial cells and also MMPs

192
Q

Why might surgery removing the primary tumour cause domant mets to grow?

A

? production of anti-angiogenic factors by certain tumours inhibits growth of micro-mets

Surgery induces angiogenic growth factors

193
Q

What is HIF?

A

HIF is a heterodimic transcription factor comprising of one HIF-1α and HIF-1β
Activity of HIF is regulated by oxygen concentration, not mRNA expression via HIF-1α

194
Q

What happens to HIF under normoxic conditions?

A

HIF-1α hydroxylated by prolyl-4 hydroxylase - acts as a direct oxygen sensor by linking molecular oxygen to specific proline residues
VHL binds to hydroxylated HIF-1α and activates proteins which ubuitinate it -> degraded -> target genes are not activated

195
Q

What happens to HIF under hypoxic conditions?

A

Enzymes prolyl-4 hydroxylase is inactivated.
HIF-1α is rapidly stabilised and transported to nucleus
Heterodimeric HIF transcription factor can activate its target genes via hypoxia response element (HRE)
Most notable target is VEGF gene which has a HRE in its promoter region

196
Q

What happens to HIF-1α in kaposi’s sarcoma?

A

HIghly vascularised tumour caused by herpes virus
three protein products of viral genome increase HIF-1α half life, nuclear localisation and transactivation under normoxic conditions mimicking hypoxia.

197
Q

30 oncoproteins have been shown to tip balance towards angiogenesis, can you name the star players?

A 
EGFR - receptor tyrosine kinase
Src - intracellular tyrosine kinase
Ras - intracellular transducer
Fos and Jun - transcription factors
p53- normally binds to and activates the promoter of thrombospondin- 1 gene (anti-angiogenic), when p53 is mutated it does not activate it
198
Q

Describe the process of angiogenic sprouting?

A

In response to angiogenic signals, endothelial cells extend filopodia and migrate towards signal
At location of highest concentraion of VEGFA, VEGFR-2 is activated.
Signal enhanced by co-receptor neuropilin-1 (Nrp-1) and transduced via MAPK cascade
Stimulates formation of tip cell at forefront of a sprout
Behind tip cell are the proliferating stalk cells that extent the sprouting vessel
Upon VEGFR2 activation tip cells produce and release Notch ligand called Delta-like 4 (DLL4)
DLL4 binds to notch receptor on neighbouring cells -> NCID is released intracellularly -> travels to nucleus and represses VEGFR2 expression and increases VEGFR1 expression.
This means the growing sprout moves along the VEGF gradient.

199
Q

Name some carcinogenic contaminents on foods?

A

Farmed salmon - contains polychlorinated biphenols and other pesticides, eating >once a month increases cancer risk

Meat - cooking at high temps produces heterocyclic amines -> DNA adducts -> base substitutions and mutations

Peanuts-> contaminated with aflatoxin B, a fungal product of aspergillus flavus -> cause GC->TA transversions -> HCC

200
Q

What is folate and why is it so important?

A

Vitamin B9
CAn accept or donate one carbon units in metabolic reactions
Critical co-enzyme for nucleotide synthesis and DNA methylation - depletion can interfere with this and cause cancer.

201
Q

What happens to DNA synthesis in a person with folate def?

A

dTMP synthesis is inhibited in a low folate state and imbalance of nucelotides results in incorporation of uracil into DNA -> DNA strand breaks trying to repair this

Also get disruption in DNA methylation may cause genomic hypomethylation
- methyl groups used for methylation are supplied by folate -> decrease in synthesis of methionine and so genomic hypomethylation

MUTATION AND HYPOMETHYLATION

202
Q

Why does obesity cause cancer?

A

Adipose tissue is an endocrine tissue that can release free fatty acids, peptide and steroid hormones.

ALTERED SEX HORMONE METABOLISM

  • synthesis of oestrogen from androgens using aromatase
  • elevated cholesterol - 27-hydroxycholesterol is a ligand for oestrogen receptor

INCREASED PRODUCTION OF FAT CELL HORMONES- ADIPOKINES
- causes chronic inflammatory response -> IL6, TNF

INCREASED INSULIN SIGNALLING PATHWAYS
- promotion of proliferation and inhibition of apoptosis

DIETARY ALTERATIONS OF GUT MICROBIOTA
- promotes liver cancer -> more gram +ve => causes increase in bacterial metabolite deoxycholic acid -> chronic DNA damage in liver

203
Q

Why does alcohol cause cancer?

A

Metabolised by enzyme alcohol dehydrogenase to form acetaldehyde -> binds to DNA -> forms adducts
Get more acetaldehyde in saliva (10-100x higher) as bacteria in saliva convert it.

Acetaldehyde is oxidised by enzymes acetaldehyde dehydrogenase (single nucleotide polymorphism of gene causes intolerance and increased risk of oesophageal cancer)

204
Q

How is fruit and veg intake linked to cancer?

A

Inverse assoc between total fruit and veg intake and risk of cancer
Microconstiuents of food play a role in cancer prevention directly via free radical scavenging or indirectly regulating expression of genes that code for phase I and II reactions

Phase I and II reactions are major defence mechanism against xenobiotics (foreign substances) - often phase I converts to ultimate carcinogen and phase II allows removal.

205
Q

How does vitamin c help protect against cancer?

A

Water soluble vit C can donate electrons to a free radical
Oxidised vit c forms asorbyl radical that is fairly stable and unreactive
Vit C reductase can regenerate vit C from ascorbyl radical for reuse or ascorbyl radical may lose another electron and become degraded
Vit C needs to be replenished daily
Lipid soluble vit E acts as a free radical scavenger in a similar way

206
Q

What is the role of antioxidants in cancer?

A

Antioxidant response element (ARE) in promoter region of several genes encoding detoxification and antioxidant enzymes (eg gluathione s-transferase, NADPH)

Both antioxidants and carcinogens bind to KEAP1 in cell and prevent it from interacting with transcription factor Nrf2.
Nrf2 binds to Maf (member of basic leucine zipper family) and activates transcription of detoxification enzymes

Antioxidants:

  • Isopthiocyanates in broccoli
  • EGCG in green tea
207
Q

What is the warburg effect?

A

Observation that cancer cells carry out aerobic glycolysis, converting glucose to lactate in presence of oxygen.

208
Q

Normally in aerobic conditions how does a cell make ATP?

A
  1. Glucose undergoes glycolysis in cytoplasm to pyruvate x2
  2. Pyruvate converted to acetyl coA by pyruvate dehydrogenase - oxidative process, NADH and CO2 formed.
  3. Citric acid/Krebs cycle - series of reactions breaks down acetyl coA - > forms ATP, NADPH, FADH2
  4. Electron transport chain - series of mitochondrial membrane proteins that transfer electron donors to electron receptors
209
Q

What is the bodies 1st, 2nd and 3rd line defense of pathogens?

A

1st line = skin and mucous membranes

2nd line = no memory

  • phagocytes
  • inflammation
  • complement
  • cytokines

3rd line = specific and adaptive

  • b and t lymphocytes
  • antibodies
210
Q

What are PRRs?

A

Pattern recognition receptors
Mainly found on antigen presenting cells (APCs) like dendritic cells, monocytes, NK cells, also found on other non-immune cells.

Recognise PAMPs (pathogen assoc molecular patterns) and TFs
INNATE IMMUNITY
When PAMP binds to PRR -> recruitment of APCs, upregulation of MHC and secretion of cyto/chemokines

211
Q

What happens in complement cascade?

A

Innate immunity

Classical pathway -> activated by antigen/antibody complexes -> starts at C1

Alternative pathway -> activated by cell membranes -> starts at C3b

Lectin pathway -> activated by carbohydrate structures -> starts at MBL

OUTCOMES:
C3b -> causes OPSONISATION
C3a & C5a -> inflammation, mast cell activation/chemotaxin
MAC -> LYSIS

212
Q

What causes opsonisation

A

Activation of complement cascade

Specifically C3b

213
Q

Name some acute phase proteins and how do they affect the complement system?

A

IL6, IL1, TNF-α -> cause acute phase proteins to be made -> CRP, mannan-binding lectin, serum amyloid protein A

Maximise activation of complement system
CRP and serum amyloid protein A bind to DNA and other nuclear material from cells helping in their clearance

214
Q

What are interferons and when are they produced?

A

Produced in reponse to viral infection

Inhibit protein synthesis

215
Q

What are lymphokines?

A

GF for lymphocytes eg IL2, IL4, influence nature of immune reponse

216
Q

What are monokines?

A

Critical to immune defence and inflammation eg IL1, TNF, IL6- activate lymphocytes, increase body temp, activate mobilise phagocytes, activate vascular endothelium

217
Q

What are chemokines?

A

Activate and direct effector cells expressing appropriate chemokine receptors to sites of tissue damage and regulate leukocyte migration to tissues. eg CXCL-8, CCL2

218
Q

What are MHC class I cells?

A

Most nucleated cells

Present antigen to cytotoxic T cells (via MHC receptor)

219
Q

What MHC class II cells?

A

B cells, macrophages and dendritic cells

Present antigen to helper T cells (via T cell receptor)

220
Q

What is CD8+? Which cells have it and what does it do?

A

CD8 is a transmembrane glycoprotein that serves as a co-receptor for the T cell receptor.
SPECIFIC FOR MHC CLASS I
CD8+ cells become cytotoxic T cells on activation

221
Q

What is CD4+? Which cells have it and what does it do?

A

CD4 is a transmembrane glycoprotein that serves as a co-receptor for the T cell receptor.
SPECIFIC FOR MHC CLASS II

CD4 cells can be T helper cells, monocytes, macrophages, dendritic cells.

222
Q

What encodes the MHC proteins in humans?

A

HLA genes on chromosome 6

223
Q

What makes up a T cell receptor?

A

2 different protein chains - heterodimer

  • 95% are α/β chains
  • 5% are γ/δ chains

Transmembrane region
Constant region
Variable region at top with antigen binding site

224
Q

What 3 signals does a naive T cell need for activation?

A
  1. Antigen presented by APC via MHC recognised by TCR
  2. Co-stimulatory activation by checkpoint moleculres eg WCD28 (t cell) and B7 (APC)
  3. Cytokines
225
Q

What inhibitory molecules are activated following naive T cell activation?

A

CTLA4- co-inhibitory molecule is rapidly mobilised from intracellular vesicles within T cell membrane
It competes for B7 ligand (on APC) with C28, it has a higher affinity for it so inhibits it

PD1 and its ligands PDL1 and PDL2 are also co-inhibitory.
Interaction of PDL1 on tumour cells and its receptor on activated effector T cells causes recruitment of SHP-2 phosphatases and inactivation of PI3K blocking production and secretion of molecules required for cytotoxic reponse.

226
Q

What cells have PD1, PDL1 and PDL2 receptors?

A

PDL1 - tumour cells and many other types of cells
PDL2 - APCs

PD1 - T cells

227
Q

If there is an intracellular cytosolic microbe - describe the process of presentation? Which MHC class is used?

A

Antigen processed - peptides

Taken into the endoplasmic reticulum. Bind to CLASS I MHC -> golgi -> vesicle and transported to cell surface

228
Q

If there is an extracellular antigen in vesicles - describe the process of presentation? Which MHC class is used?

A

Antigen taken up into cell via endocytosis
Degraded by phagosomes in vesicle
MHC class II released from ER
Travels to vesicle and combine with antigen
Travels to cells surface and presents it

229
Q

What do antibodies do?

A

Neutralisation
Opsonisation
Complement activation
Antibody-dependent cellular cytotoxicity

230
Q

Describe the components of an antibody?

A 
2 identical binding sites
2 heavy chains
2 light chains
Linked by disulphide bonds
Each chain has a constant and variable region
231
Q

What is IgM, IgG, IgA, IgE, IgD - how are thye made up, where are they important and what do they do?

A

IgM (6%) - pentamer- activates complement cascade
IgG (80%) - monomer - neutralises toxins, opsonisation, complement, binds to phagocytes
IgA (13%)- dimer- secreted in tears, mucus, saliva
IgE (0.002%)- monomer- allergy, binds to mast cells/basophils
IgD (1%) - monomer- B cell receptor

232
Q

What do B cells do?

A

Interact with helper T cells then turn in plasma cells that produce antibodies. Antigen presented via MHC class II

233
Q

How do T cells build tolerance?

A

Central - thymus

  • negative selection
  • receptor editing
  • generation of regulatory t cells

Peripheral

  • clonal anergy (unreponsive, prevent overactivation)
  • clonal deletion
  • regulatory t cells
  • T-T cell interactions

Maturation happens in response to antigen

234
Q

What are Treg cells and what is their role in cancer?

A

Type of differentiated T helper cell -> T regulatory cell -> influence tolerance and immune suppression
Secrete immunosuppresive cytokines (IL10, TGFb)
Block T cell proliferation, inhibit NK function
High levels of Tregs = poor prognosis in cancer

235
Q

During tumour development the immune system responds in different ways which are…

A

Elimination -> equilibrium -> escape

236
Q

What are TILs and how do they affect prognosis?

A

T infiltrating lymphocytes (TILs)

  • can predict favourable outcome in some tumour types
  • infiltrating NK and CD8 T cells assoc with favourable prognosis
237
Q

Why doesn’t our immune system protect us from cancer?

A

Peripheral tolerance is required to regulate self reactive T cells and NK cells- these regulatory mechanisms are often exploited by tumours to evade immune recognition

TUMOUR IMMUNE INVASION VIA:

  • MODIFYING MICROENVIRONMENT- secrete immunosuppressive agents eg TGF-B, IL-10, VEGF
  • EVADES T CELL RECOGNITION- downregulates class I MHC (NK cells should still recognise cells that have lost MHC)
  • DYSREGULATION OF ANTIGEN PROCESSING/PRESENTATION PATHWAYS
238
Q

What are good immune cells?

A

CD8 T cells, NK cells, CD4 (TH1), M1 polarised MACs

239
Q

What are the bad immune cells?

A

CD4 Tregs, MDSCs, TAM, M2 MACs

240
Q

What are types tumour associated antigens?

A

Can be unique to cancer- neoantigens
Overexpressed antigens eg HER2
Differentially expressed antigens eg cancer testis angigens which are normally restricted to testis germ cells

241
Q

What are dendritic cells?

A 
Type of APC
Have class I and II MHC
Immature dendritic cells - specialised for antigen acquisition, highly phagocytic, low in class II, co-stimulatory, no NK activation

Mature DC: antigen and danger signal specialised for antigen presentation of T cells, less phagocytic, high class II, co-stimulatory molecules, activate NK cells

242
Q

What danger signals activate innate and adaptive immunity?

A

Tumour necrosis cores
Hypoxia
Cell derived danger signals - heat shock proteins, ATP, RNA, DNA, uric acid, hyaluronic acid, NK ligands, IFN-a

243
Q

How does radiotherapy cause immunogenic cell death?

A

senses presence of cytosolic DNA -> activates CGAS -> STING (stimulator of interferon genes)

Inhibited by TREX1

244
Q

What is a tumour assoc macrophage and what does it mean in cancer?

A

Poor prognosis
Secrete IL10, TGFb
Enhance tumour proliferation through NFKB/STAT signalling

245
Q

What is the danger hypothesis?

A

Based on idea that the immune system does not differentiate from self/non-self but by things that might cause danger via danger signals

246
Q

What is the infectious non-self model?

A

That APCs are activated via pattern recognition receptors (PRRs) which recognize evolutionary distant conserved patterns. These pathogen-associated molecular patterns (PAMPs) on such organisms as bacteria are recognized as infectious non-self, whereas PRRs are not activated by non-infectious self.

DOES NOT EXPLAIN ANTI-TUMOUR IMMUNITY

247
Q

What is a myeloid suppressor cell?

A

Necrosis releases endogenous DAMPs, starts the cycle of chronic inflammation and recruits MDSC
Produce NO and ROS may cause DNA damage and mutations
Support tumour progression by increasing angiogenesis, tumour cell stemness, metastasis

248
Q

Which chemotherapies are immunogenic?

A

Anthracyclines

Gemcistabine - decreases tregs and MDSCs, increases IFNg producing CD8 cells

249
Q

Is cyclophosphamide immune stimulatory or suppressive?

A

Low dose- ablates Tregs, promotes DC maturation and enahnces NK cell lysis & T cell proliferation

High dose- reduced T cell proliferation and T cell apoptosis

250
Q

How do taxanes affect immune system?

A

Activate MACs, stimulate cytokine secretion

But also inhibit NK and T cells

251
Q

What is EBV and how does it cause cancer?

A

DNA virus
Causes lymphoma eg Burkitts, nasopharyngeal cancer
EBV encodes several viral proteins that affect host gene expression- oncoprotein LMP1 able to transform cells in culutre
Activates genes promoting proliferatoin eg EGFR, Bcl-2

252
Q

What is HPV and what types cause cancer? How do they do this?

A

DNA virus
HPV 16 & 18
HPV gene products E6 & E7 are major players that target tumour suppressors
- E7 binds to and triggers degradation of Rb preventing sequestering of E2F -> constiutive action of cyclin A/E
-E6 forms a complex with ubquitin ligase binds to p53 and targets it for degradation

Can cause cervical, oral, penile, vulval, anal cancer

253
Q

What is HTLV-1? How do you get it and how does it cause cancer?

A

RETROVIRUS
adult T cell leukaemia (2-5% affected individuals get leukaemia)
Transmission via breast milk, semen, blood
Genomic RNA copied into DNA by reverse transcriptase before viral proteins are synthesised by the host cells machinary
-TAX protein key player in mechanism of carcinogenesis

254
Q

What is hepatitis B and how does it cause cancer?

A

DNA virus
Chronic infection causes HCC
Causes cancer via:
- evoking immune response, chronic inflammation - liver necrosis and regeneration
- insertional mutagenesis at specific sites-> integration into human telomerase reverse transcriptase (hTERT) gene occurs frequently, results in upregulation due to close proximity with viral enhancer
- HBV X protein activates proto-oncogenes (main effector)

255
Q

What causes primary effusion lymphomas and Kaposi’s sarcoma and how does it cause them?

A

Herpes virus 8 or karposi’s sarcoma assoc herpes virus
DNA virus
Thought to infect circulating endothelial cells.
Often assoc with AIDs
KSHV produces viral cyclin, viral anti-apoptotis proteines eg vBcl2, viral encoded mRNAs and viral protein LANA (main effector) which interferes with p53 and Rb
They require autocrine and paracrine factors for tumourigenesiss

256
Q

How does gastric mucosa change to cancer?

Cause?

A

75% gastric cancers caused by HPV
Chronic superficial gastritis -> atrophic gastritis -> intestinal dysplasia -> gastric carcinoma.

Gastric atrophy characterised by loss of normal glandular tissue and results in reduced acid production -> other bacteria colonise -> inflammatory reponse

257
Q

How does H.pylori cause cancer?

A

Code for protein called cytotoxin-associated antigen (Cag A)- effector protein injected into cells via integrin receptor -> phosphorylated by Src -> MAPK pathway

Unphosphorylated Cag A interacts with e-cadherin causing it to release b-catenin -> nucleus and is transcriptional regulator of genes required for metaplasia

Also inflammation results in hypermethylation of promoter of e-cadherin, reducing its expression

Cag-A expression induced in high salt conditions

258
Q

The inflammatory pathways involved in oncogenesis activate 2 important transcription factors, what are they?
What other ways does inflammation cause cancer?

A

STAT -> induces cycle D &B, myc genes, Bcl-2
NF-κB -> regulate pro-inflammator factors

Leucocytes produce ROS and NOS to help fight infection but can also cause DNA damage
TNF-a can affect cell motility and tumour metastasis -> nitric oxide synthase is stimulated by TNF-a
IL-6 important in hepatocarcinogenesis - downregulation of IL6 by macrophages in response to oestrogen makes women less susceptible

259
Q

What is NF-κB? What is its role in cancer?

A

Transcription factor
Activated by specific inflammatory agents eg bacteria, viruses, cytokines eg TNF-a, stress, hypoxia, smoke, carcinogens

Causes inflammation, promotes metastasis/angiogenesis, and inhibits apoptosis
Target genes : c-Flip, Cox-2, MMP9, VEGF, IL6, TNF-a

Normally bound to IκB proteins which inhibits NF-κB, if these are degraded then NF-κB released and travels to nucleus.

260
Q

What are the hallmarks of cancer?

A
  1. Sustained proliferative signalling
  2. Insensitivity to anti-growth signals
  3. Evasion of programmed cell death
  4. Replicative immortality
  5. Induced angiogenesis
  6. Activating invasion + metastasis

+ emerging

  1. Avoid immune destruction
  2. Tumour promoting inflammation
  3. Genome instability and mutations
  4. Desregulating cellular energetics
261
Q

What is a single nucleotide polymorphism?

A

Change in a single base eg A-> G
Most either synonymous or benign
Specific SNPs in particular genes may be assoc with increased or decreased risk of cancer.

262
Q

How are mutations classified?

A

5 point classification - whether a change in amino acid changes function of protein
1. clearly not pathogenic
2. Likely non-pathogenic
3. Uncertain
4. Likely pathogenic- exchange hydrophobic for hydrophilic which changes structure of protein
5, clearly pathogenic

263
Q

What is HNPCC and how is it inherited?

A

Lynch syndrome
AD
Causes colorectal, endometrial, small bowel, ovarian serous cystadenoma

Mutations in mismatch repair genes -> MSH2, MLH1, PMS2, MSH6 -> leads to microsatellite instability

264
Q

Name some gain of function mutations of CPGs that cause cancer

A

11 CPGs activated by mutations - all autosomal dominant
ALK- generally only somatic
EGFR- generally on somatic
RET- common somatic, can be germline in MEN2

265
Q

Name some loss of funtion mutations in CPGs?

A

103 CPGs contain loss of function mutations
TP53
BRCA1
MLH1
Herogenous - retinoblastoma (single gene)

266
Q

What are cancer associated SNPs?

A

single nucleotide polymorphism
Contribute to increased risk but not high risk like CPGs
Some protective, some increase risk
Multiplicative effect as each one may only increase risk a small amount but together risk might be much higher

267
Q

What is Li-Fraumeni?

WHat cancers does it cause?

A

TP53 germline mutation
AD
Adrenocortical, choroid plexus tumours (quite specific, all should be referred for testing)
Also sarcomas, breast, brain tumours, leukaemia

RADIOSENSITIVE - sarcomas
Very sensitive to carcinogens

268
Q

Which patients would you consider testing for Li-fraumeni? If test was positive how would you follow them up?

A

Breast cancer <30yrs esp if HER2 +ve
FH sarcoma
Choroid plexus tumours
Very high rates of early onset solid tumours over multiple generations

Annual MRI breast from age 20yrs
? annual whole body MRI

269
Q

What is MEN1?
Inheritance
Cancers

A

Mutation of MEN1 gene
AD

  • Parathyroid -90% onset 20s
  • Pancreatic - 70% - gastrinoma/insulinoma/non-functioning
  • Pituitary - adenoma 30-40%, prolactinoma 20%
270
Q

How do you monitor and treat people with MEN1?

A

Parathyroid- annual PTH, calcium, removal of 3.5/4 parathyroid glands
Pancreatic- annual gastrin, annual imaging
Gastrinomas- PPI/resection
Pit - annual prolactin and IGFR

271
Q

What is MEN2A?
Inheritance
Cancers

A

RET gene - mutations in extracellular cysteins cause intermolecular disulfide bonds -> constitutive RET dimerisation and aberrant activation
AD

Medullary thyroid cancer- 90%
Phaeochromocytoma 50%
PArathyroid adnoma 20-30%
Or familial medullary thyroid cancer- 100% risk but don’t get other cancers, 10 people in family with medullary thyroid cancer

272
Q

How do you screen people with MEN2A?

A

Annual calcitonin
Thyroidectomy
From age of 8 or 20 - annual calcium PTH, urinary metanephrines and MRI bado if positive

273
Q

What is MEN2B?
Inheritance
Cancers

A

RET mutation - alters substrate binding pocket of tyrosine kinase domain via substitution -> increase kinase activity
AD

Medullary thyroid cancer >90%
Phaeochromocytoma 40-50%
Assoc abnormalities 
- marfanoid
- mucosal neuromas
- megacolon
274
Q

What is von hippel lindau syndrome and what are the features?

A

VHL gene mutation
AD

Clear cell renal cancer
Cysts in kidneys, pancreas, genital tract
Retinal angiomas - Haemangioblastomas
Cerebellar or spinal haemangiomas
Phaochromocytomas
Endocrine pancreatic tumours
Cystadenomas
Endolymphatic sac tumours of inner ear
275
Q

Would you test all patients with clear cell renal cancer?

A 
Yes if any other features of VHL /other genetic syndrome
Or if :
<40
Bilateral
Multifocal
276
Q

What causes familial melanoma and when do you develop melanoma?

A

CDKN2A mutations - gene contains instructions for making p16 and p14
CDK4 mutations

Multiple primaries at young age of onset

  • at least 3 melanomas in family
  • risk pancreatic cancer
277
Q

What are the major and micro criteria for Cowdens syndrome?

A

Major criteria (3 or more, must be macrocephaly)

  • Macrocephaly (>97th centile) ALWAYs - do they have trouble buying hats
  • Breast cancer
  • Non-medullary thyroid cancer
  • Endometrial cancer

Minor criteria (2 major + 3 minor)

  • other thyroid lesions
  • IQ <75
  • Hamartomatous intestinal polyps
  • fibrocystic disease of breast
  • GU tumours or malformations
  • uterine fibroids
278
Q

What is the mutation responsible for cowdens syndrome?

A

PTEN

Also called hamartoma syndrome

279
Q

What is peutz-jegher syndrome?
Inheritance
Features

A

Mutations in STK11 gene- tumour suppressor gene
AD
Increase in harmatomatous polyps
Dark brown macules around mouth and oral mucosa
Cutaneous and GI symptoms
50% have cancer by age 60yrs- breat, GI, pancreas, ovary, uterus, testicle, oesophagus, lung

280
Q

What is the STK11 gene?

A

Mutated in peutz-jegher syndrome
Provides instructions for making serine/threonine kinase 11 - a tumour suppressor that helps to polarise cells and promotes apoptosis

281
Q

What causes FAP
Inheritence
Cancer

A

APC gene germline mutation on chromosome 5q21 - causes activation of Wnt pathway
Colorectal cancer age 30-40yrs

282
Q

What is gardner syndrome?

A

Subtype of FAP characterised by osteomas, dental anomalies, epidermal cysts and soft tissue tumours

283
Q

What causes neurofibromatosis type 1

Features

A

Mutation of NF1 gene -> makes protein neurofibromin- acts as a tumour suppressor in oligodendrocytes, schwann cells
Non functioning neurofibromin cannot regulate cell growth and division -> tumours along nerves

  • neurofibromas
  • Lisch nodules
  • cafe au lait and freckles
  • malignant peripheral nerve sheath tumours
  • increased risk of brain tumours and leukaemias
284
Q

How is NF1 inherited?

A

AD

1/3000-4000

285
Q

How is xeroderma pigmentosa inherited?

A

AR

286
Q

What does xeroderma pigmentosa cause ?

A

Extreme sensitivity to UV sunlight
Burn at young age, by age of 2 freckling in sun exposed areas
1/2 develop skin cancer by age 10 without sun protection (SCC, BCC or melanoma)
Blindness/cataracts/corneal ulcerations and 30% get progressive neurological deficits involving eyes, ears, balance

287
Q

What is xeroderma pigmentosa caused by?

A

9 types of mutation

Mainly in NER (nucleotide exicision repair) - XPC, ERCC2, POLH account for most

288
Q

What is Cockaynes syndrome?
Features
Inheritence

A

Rare form of dwarfism
+ deafness and retinal atrophy, microcephaly
UV sensitivity
Age quickly, 3 types starting at birth or childhood

AR mutation of ERCC6/8 gene -> involved in NER

289
Q

What syndromes cause radiosensitvity?

A 
Li-fraumeni - sarcomas
Ataxia telangiectasia
Bloom syndrome
Nijemegen breakage syndrome
Gorlin syndrome
Fanconi syndrome
290
Q

How is ataxia telangiectasia inherited ?

A

AR

291
Q

What causes ataxia telangiectasia? What are the features?

A 
ATM mutation
AR
- Mask like face
- slow eye movement
- ataxia
- telangiectasia
- radiosensitive
- cancer risk x 100 of lymphoma + leukaemia
Chromosome 11q22
1/100-200 people are carriers- higher in askenazi jews
292
Q

What is nijemegen breakage syndrome?

A 
Mutation of NBN gene - part of MRN complex (MRE11, RAD50, NBS) used in HR and activated by ATM
AR
Short stature
Mental retardation
Microcephaly
Facial dysmorphism
Immunodeficiency
Increased risk of breast cancer

RADIOSENSITIVITY

293
Q

What is Bloom syndrome?

A

Mutation in BLM gene - codes for RecQ helicase - responsbile for maintaining DNA structure and unwinding it -> increased sister chromatid exchanges

Short stature
Sun sensitive rash
Bird like features
high pitched voice
COPD
DM
Immuno def
Increased cancer risk - H+N, SCC
Radiosensitivity
294
Q

Cancer cells need rapid ATP production but glycolysis only produces 2 ATP, how else can they make ATP and synthesis macromolecules?

A

Upregulate glutamine -> enter TCA cycle
Glutamine can do reverse TCA cycle and once converted to a-ketoglutarate this can undergo reductive carboxylation and form citrate -> major substrate for lipid synthesis.

295
Q

How is the PI3K pathway influencing cancer metabolism?

A

PI3K/AKT pathway may regulate glucose metabolism by:

  1. Regulating glucose transporter expression through AKT -> stimulates transcription of GLUT1
  2. Enhancing glucose capture by HK2 and inducing aerobic glycolysis by promoting HK2 bidning to voltage dependent anion channels
  3. Stimulates PFK1 activity
296
Q

After irradiation which part of cell cycle is a cell most likely to arrest in?

A

Following ionizing radiation exposure, virtually all proliferating cells (independent of p53 (TP53) status) will show a radiation dose-dependent arrest in the G2 phase. Typically, cells with functional wild-type p53 will also arrest in the G1 phase of the cell cycle, and some cells may also arrest in S phase after radiation.

FRCR Clinical Oncology Part 1 COPY (5 decks)

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