Tumour biology Flashcards

Question

What is a tautomeric shift?

Answer 1

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

Answer 2

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

Answer 3

``` Direct repair Base exicision repair- most common Nucleotide exicison repair Mismatch repair DSB repair - HR - NHEJ ```

Answer 4

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

Answer 5

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

Answer 6

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

Answer 7

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

Answer 8

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

Answer 9

Corrects errors that arise spontaneously during DNA replication

Answer 10

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

Answer 11

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.

Answer 12

- 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.

Answer 13

Quick 2-4hrs LOST DNA, MUTAGENIC

Answer 14

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.

Answer 15

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

Answer 16

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.

Answer 17

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

Answer 18

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

Answer 19

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.

Answer 20

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.

Answer 21

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

Answer 22

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

Answer 23

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 ```

Answer 24

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

Answer 25

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

Answer 26

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

Answer 27

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.

Answer 28

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

Answer 29

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.

Answer 30

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.

Answer 31

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

Answer 32

Histone modification DNA methylation Both can be acquired or inherited.

Answer 33

Acetylation Methylation Phosphorylation Ubquination

Answer 34

``` 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.

Answer 35

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.

Answer 36

Addition of methyl group to position 5 of cytosine | ONLY occurs at cytosine nucleotides which are situated 5' to guanine (CpGs)

Answer 37

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

Answer 38

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

Answer 39

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.

Answer 40

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

Answer 41

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

Answer 42

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

Answer 43

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

Answer 44

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

Answer 45

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

Answer 46

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

Answer 47

``` 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

Answer 48

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)

Answer 49

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

Answer 50

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

Answer 51

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.

Answer 52

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.

Answer 53

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

Answer 54

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

Answer 55

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

Answer 56

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

Answer 57

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

Answer 58

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)

Answer 59

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

Answer 60

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

Answer 61

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

Answer 62

On passing G1 restriction point

Answer 63

``` 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 ```

Answer 64

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.

Answer 65

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

Answer 66

Important for G1-S phase progression | Binds to cdk2

Answer 67

Important for S phase progression | Binds to cdk2

Answer 68

Directs G2 and G2->M phase | Binds to cdk1

Answer 69

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

Answer 70

- 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.

Answer 71

Rb protein

Answer 72

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

Answer 73

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.

Answer 74

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

Answer 75

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

Answer 76

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

Answer 77

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

Answer 78

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

Answer 79

BRCA1/2 PTEN Rb p53

Answer 80

Hereditary syndromes that cause cancer predispositions

Answer 81

Recruitment of Rad51 to DSBs - HR

Answer 82

More diverse role in HR and regulation of transcription

Answer 83

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

Answer 84

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

Answer 85

Cowden disease | - harmartomas, risk of breast, endometrial and thyroid tumours

Answer 86

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

Answer 87

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.

Answer 88

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

Answer 89

Cell cycle arrest or senescence DNA repair Apoptosis Inhibition of angiogenesis

Answer 90

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

Answer 91

Regulated at level of protein degradation not gene expression Main regulator = MDM2 Other regulators: MDMX and HAUSP (removes Ubiquitin form p53)

Answer 92

``` 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 ```

Answer 93

p53 stimulates production of MDM2 | Low amounts of p53 will reduce transcription of MDM2

Answer 94

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

Answer 95

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

Answer 96

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

Answer 97

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

Answer 98

Phosphorylation of Ser46 results in preference for apoptosis | Absolute levels of p53 and transcription factors affect response

Answer 99

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

Answer 100

>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.

Answer 101

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

Answer 102

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.

Answer 103

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

Answer 104

Adenovirus E1A, papillomavirus E6 & E7 etc inactivate Rb. Some do this using uquitin-proteosome system to degrade it.

Answer 105

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

Answer 106

Highly regulated process of programmed cell death, active process.

Answer 107

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

Answer 108

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

Answer 109

``` 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)

Answer 110

c-Flip | Binds to FADD or caspase 8 and inhibits caspase 8 recruitment and activation

Answer 111

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.

Answer 112

Cause dissociation of Bax oligomers from the mitochondrial membrane

Answer 113

BH3- only, pro apoptotic - Bad - Bik - Bid - Bim - Noxa - Puma Pro apoptotic other members - Bax - Bok - Bak

Answer 114

``` Bcl-2 Bcl-w A1 Boo Mcl-1 Bind to and inhibit pro-apoptotic proteins ```

Answer 115

MOMP | Mitochondrial Outer Membrane Permeabilisation

Answer 116

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

Answer 117

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

Answer 118

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

Answer 119

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

Answer 120

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

Answer 121

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

Answer 122

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.

Answer 123

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

Answer 124

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.

Answer 125

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

Answer 126

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)

Answer 127

Wnt1 is a proto-oncogene | Mutations constiutively activated Wnt pathway

Answer 128

Colorectal , >90% | Most mutations inactivate APC or activate β-catenin (rarely affect Wnt)

Answer 129

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

Answer 130

Role in embryonic development, tissue self renewal and carcinogenesis Cilia

Answer 131

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.

Answer 132

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

Answer 133

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)

Answer 134

Patched is a tumour suppressor gene

Answer 135

Gorlin syndrome- germline mutation in one copy of patched -> BCC, medulloblastoma, rhabdomyosarcomas All sporadic BCCs 30% sporadic medulloblastomas

Answer 136

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

Answer 137

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

Answer 138

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

Answer 139

EMT- epithelial-mesenchymal transition | Conversion of closely connected epithelial cells into highly mobile mesenchymal cells.

Answer 140

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

Answer 141

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

Answer 142

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

Answer 143

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

Answer 144

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

Answer 145

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)

Answer 146

Altered expression of receptors observed in tumour cells during EMT

Answer 147

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.

Answer 148

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.

Answer 149

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

Answer 150

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.

Answer 151

Tumour cells within the bloodstream | Can travel singly or in clumps together with platelets as emboli

Answer 152

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

Answer 153

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.

Answer 154

Disseminated tumour cells | cells that have spread but have not yet colonised.

Answer 155

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

Answer 156

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.

Answer 157

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

Answer 158

Non specific growth factors - EGF, HGF, FGF, PDGF Vascular endothelium specific growth factors - VEGF & VEGF-R - MAIN PLAYER - angiopoeitins - Tie receptors

Answer 159

5 members VEGF-A-D and placental growth factor (PIGF) 3 VEGF tyrosine kinase receptors - VEGFR -1, -2, -3

Answer 160

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

Answer 161

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

Answer 162

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

Answer 163

``` Angiostatin ENdostatin Prolactin P53 Thrombospondin-1, -2 ```

Answer 164

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

Answer 165

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

Answer 166

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

Answer 167

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

Answer 168

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

Answer 169

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

Answer 170

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.

Answer 171

``` 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 ```

Answer 172

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.

Answer 173

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

Answer 174

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.

Answer 175

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

Answer 176

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

Answer 177

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)

Answer 178

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.

Answer 179

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

Answer 180

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

Answer 181

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

Answer 182

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

Answer 183

1st line = skin and mucous membranes 2nd line = no memory - phagocytes - inflammation - complement - cytokines 3rd line = specific and adaptive - b and t lymphocytes - antibodies

Answer 184

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

Answer 185

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

Answer 186

Activation of complement cascade | Specifically C3b

Answer 187

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

Answer 188

Produced in reponse to viral infection | Inhibit protein synthesis

Answer 189

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

Answer 190

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

Answer 191

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

Answer 192

Most nucleated cells | Present antigen to cytotoxic T cells (via MHC receptor)

Answer 193

B cells, macrophages and dendritic cells | Present antigen to helper T cells (via T cell receptor)

Answer 194

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

Answer 195

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.

Answer 196

HLA genes on chromosome 6

Answer 197

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

Answer 198

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

Answer 199

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.

Answer 200

PDL1 - tumour cells and many other types of cells PDL2 - APCs PD1 - T cells

Answer 201

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

Answer 202

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

Answer 203

Neutralisation Opsonisation Complement activation Antibody-dependent cellular cytotoxicity

Answer 204

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

Answer 205

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

Answer 206

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

Answer 207

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

Answer 208

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

Answer 209

Elimination -> equilibrium -> escape

Answer 210

T infiltrating lymphocytes (TILs) - can predict favourable outcome in some tumour types - infiltrating NK and CD8 T cells assoc with favourable prognosis

Answer 211

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

Answer 212

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

Answer 213

CD4 Tregs, MDSCs, TAM, M2 MACs

Answer 214

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

Answer 215

``` 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

Answer 216

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

Answer 217

senses presence of cytosolic DNA -> activates CGAS -> STING (stimulator of interferon genes) Inhibited by TREX1

Answer 218

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

Answer 219

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

Answer 220

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

Answer 221

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

Answer 222

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

Answer 223

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

Answer 224

Activate MACs, stimulate cytokine secretion | But also inhibit NK and T cells

Answer 225

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

Answer 226

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

Answer 227

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

Answer 228

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)

Answer 229

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

Answer 230

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

Answer 231

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

Answer 232

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

Answer 233

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.

Answer 234

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 7. Avoid immune destruction 8. Tumour promoting inflammation 9. Genome instability and mutations 10. Desregulating cellular energetics

Answer 235

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.

Answer 236

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

Answer 237

Lynch syndrome AD Causes colorectal, endometrial, small bowel, ovarian serous cystadenoma Mutations in mismatch repair genes -> MSH2, MLH1, PMS2, MSH6 -> leads to microsatellite instability

Answer 238

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

Answer 239

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

Answer 240

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

Answer 241

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

Answer 242

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

Answer 243

Mutation of MEN1 gene AD - Parathyroid -90% onset 20s - Pancreatic - 70% - gastrinoma/insulinoma/non-functioning - Pituitary - adenoma 30-40%, prolactinoma 20%

Answer 244

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

Answer 245

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

Answer 246

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

Answer 247

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 ```

Answer 248

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 ```

Answer 249

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

Answer 250

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

Answer 251

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

Answer 252

PTEN | Also called hamartoma syndrome

Answer 253

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

Answer 254

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

Answer 255

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

Answer 256

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

Answer 257

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

Answer 258

AD | 1/3000-4000

Answer 259

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

Answer 260

9 types of mutation | Mainly in NER (nucleotide exicision repair) - XPC, ERCC2, POLH account for most

Answer 261

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

Answer 262

``` Li-fraumeni - sarcomas Ataxia telangiectasia Bloom syndrome Nijemegen breakage syndrome Gorlin syndrome Fanconi syndrome ```

Answer 263

``` 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 ```

Answer 264

``` 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

Answer 265

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 ```

Answer 266

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.

Answer 267

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

Answer 268

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.