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Cancer Flashcards

1
Q

What kind of gene changes may cause cancer?

A
  1. Mutations
  2. Epigenetic changes
  3. Tumour viruses
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2
Q

What are malignant tumours?

A

Tumours capable of seeding cells into the circulation to form new colonies of tumour in other parts of the body

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3
Q

What is a metastasis?

A

New colony of cancer cells distinct from site of the primary cancer

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4
Q

What causes most deaths from cancer?

A

Metastasis

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5
Q

What are the distinguishing features of a benign tumour?

A
  1. Confined to original site in body
  2. Clearly defined boundaries
  3. Can be physically separated from surrounding tissue
  4. Surrounded by capsule of connective tissue, which can be peeled away
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6
Q

What are the distinguishing features of a malignant tumour?

A
  1. Ragged edges
  2. Infiltrates into surrounding tissue
  3. Grows into surrounding tissue
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7
Q

What is invasion?

A

Infiltration of malignant tumour into surrounding tissue

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8
Q

When might benign tumours be life-threatening?

A
  1. Menangioma putting pressure on brain

2. Hormone-producing tumours of pituitary or adrenal glands

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9
Q

What is the relationship between benign and malignant tumours?

A

Malignant tumours often progress from benign tumours

Not all benign tumours form malignant tumours

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10
Q

What are the clinically important sites of metastasis?

A
  1. Brain
  2. Liver
  3. Bone marrow
  4. Lung
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11
Q

Where do breast cancers often metastasise to?

A
  1. Lymph nodes

2. Bone

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12
Q

Where do colorectal cancers often metastasise to?

A

Liver

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13
Q

What is the nomenclature for a benign tumour?

A

Tissue name + -oma

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14
Q

What is lipoma?

A

Benign fat tumour

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15
Q

What is leiomyoma?

A

Benign smooth muscle tumour

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16
Q

What is papilloma?

A

Wart

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17
Q

What is adenoma?

A

Benign glandular lump

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18
Q

What is the nomenclature for a malignant tumour from mesenchyme?

A

Tissue name + sarcoma

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19
Q

What is osteosarcoma?

A

Malignant bone tumour

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20
Q

What is leiomyosarcoma?

A

Malignant smooth muscle tumour

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21
Q

What is the nomenclature for a malignant tumour from epithelium?

A

Tissue name + carcinoma

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22
Q

What is a nevus?

A

Benign mole

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23
Q

Give two examples of malignant neural tumours

A
  1. Neuroblastoma

2. Glioblastoma

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24
Q

What is leukaemia?

A

Liquid haemopoietic neoplasms

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25
What is lymphoma?
Solid haemopoietic neoplasms
26
What is a neoplasm?
1. Abnormal growth 2. Irreversible 3. Altered architecture
27
What is hyperplasia?
Increased proliferation
28
What is metaplasia?
Changed pattern of growth Changed differentiation in tissue
29
What is dysplasia?
Abnormal pattern, such as mitoses in the wrong place
30
What occurs in metaplasia of the cervix?
Glandular epithelium of endocervix changes to squamous-like pattern
31
Where is squamous metaplasia observed?
1. Cervix | 2. Lung
32
What are the mechanisms by which cancer causes disease?
1. Pressure 2. Erosion/destruction of normal tissue 3. Epithelial ulceration 4. Competition with normal tissue 5. Tumour-specific products
33
What is cachexia?
General, systemic wasting
34
What are some of the causes of death due to cancer?
1. Failure of bone marrow in leukaemia 2. Haemorrhage through lack of platelets 3. Infection due to lack of neutrophils 4. Liver failure 5. Pain management
35
What are the most common types of cancers?
Malignant tumours from epithelium
36
How may a colorectal cancer present?
1. Patient is anaemic due to chronic bleeding of ulcerated tumour 2. Weight loss 3. Altered bowel habit
37
How may a prostate cancer present?
1. Ureter obstruction due to enlarged prostate
38
How may breast cancer present?
1. Lump in breast | 2. Bone pain or pathological fracture due to metastasis to bone
39
What are the four most common cancers?
1. Breast 2. Lung 3. Prostate 4. Bowel
40
How do cancers develop?
Successive evolution of clones that have a selective advantage over their neighbours
41
What is clonal expansion?
1. A normal cell acquires a mutation/gene change 2. Its progeny compete with neighbouring cells 3. Progeny take up more than normal share of tissue 4. One of progeny acquires further gene change that confers greater selective advantage and so on
42
Why are cells in a tumour heterogeneous?
Tumour consists of preceding clones and clones that are dead-ends in the cancer evolutionary tree
43
What is the first known change in colorectal cancer?
Mutation in either APC gene or beta-catenin gene
44
What is the third change shown in colorectal cancer?
Mutation in either KRAS or BRAF
45
What is an oncogene?
Overactivity gain of function mutation Dominant in cell
46
What is a tumour suppressor gene?
Loss of function mutation Recessive in cell
47
What is p53?
Tumour suppressor gene Significant effect seen even when only one copy is mutated as p53 forms a tetramer so most tetramers are faulty
48
What is Rb1?
Retinoblastoma protein Tumour suppressor gene Controls cell cycle Inhibits initiation of DNA replication Holds cycle at G1/S checkpoint
49
What is cyclin-dependent kinase 4?
Oncogene Complexes with cyclin D1 Phosphorylates Rb1 Removes Rb1 inhibition Allows progression through checkpoint
50
Which proteins inhibit CDK4?
p16 INK4A
51
What is the effect of genetic instability?
Cancers are more prone to undergo mutations than normal cells Have defects in DNA machinery
52
What are the two types of genetic instability?
1. Chromosomal instability | 2. Sequence instability
53
What is chromosomal instability?
Loss of mechanisms that protect cell against chromosomal aberrations Defects in DNA replication and mitosis
54
What is sequence instability?
Inactivation of DNA mismatch repair Defects in DNA repair
55
What kind of mutations directly affect DNA synthesis?
Mutations in DNA polymerase proof-reading domain
56
What kind of mutations affect components in DNA repair mechanisms?
Inability to repair chemical damage, strand breaks, cross-links
57
What are the main categories of DNA repair?
1. Dealing with damaged bases 2. Mismatch repair 3. DNA strand break and cross-link repair
58
How does mismatch repair work?
Deals with mismatched bases and small loops
59
How do mismatches occur?
Polymerases slip whilst trying to replicate repeat sequences, adding or deleting a copy of the repeat
60
What is the effect of persistent mismatches that are not repaired?
Shrinkage or expansion of microsatellites Microsatellite instability Higher point mutation rate
61
Which mutations cause defective mismatch repair in colon cancers?
Inactivation of MLH1 or MSH2
62
How is MLH1 inactivated?
Epigenetically DNA methylation of promoter
63
How are DNA crosslinks repaired?
Fanconi anaemia pathway Shares components with homologous recombination repair Operates at damaged replication forks
64
What is the function of the Brca2 gene?
1. Double-strand break repair | 2. Cross-link repair
65
What kind of genetic instability is seen in Brca2-defective breast cancers?
Chromosome instability
66
What is the effect of defects in ATM?
ATM is one of damage-signalling proteins Cells cannot detect damage as easily Contributes to instability
67
What causes chromosome instability?
1. Errors in chromosome segregation at anaphase - leads to lagging chromosomes
68
What is familial adenomatous polyposis?
Rare inherited predisposition to colon cancer Individuals develop polyps in adolescence High probability of polyps progressing to cancer Colon usually removed
69
What is hereditory non-polyposis colon cancer?
Mutations in MLH1 or MSH2 AKA Lynch Syndrome
70
On which chromosome is the retinoblastoma gene located?
Chromsome 13
71
What are the proliferation and survival changes seen in cancer cells?
1. Independence of growth-stimulating signals 2. Resistance to growth-inhibitory signals 3. Differentiation block 4. Resistance to apoptosis 5. Immortality
72
Give six examples of pro-proliferation signalling pathways
1. Wnt pathway 2. KRAS-BRAF-MAPkinase pathway 3. PI3 kinase-Akt pathway
73
What is the TGF-beta signalling pathway?
Growth inhibitory pathway
74
What is the Wnt-signalling pathway?
Transmembrane receptor pathway Mutated in almost all colorectal cancers Mutation in APC, beta-catenin or Tcf transcription factor Prevents degradation of beta-catenin by APC complex
75
What is the role of beta-catenin?
Acts with Tcf Interacts with APC Drives cell proliferation and clonal expansion
76
What are the pro-proliferative defects in Wnt-signalling?
1. Inactivation of APC | 2. Activation of beta-catenin
77
Which receptors are included in the ERBB/EGF receptor family?
1. ERBB/EGF receptor | 2. ERBB/HER2 receptor
78
What is the target of herceptin?
HER2 receptor
79
What are the two downstream signalling pathways for ERBB family signalling?
1. Ras and Raf to MAPkinase | 2. PIP3 pathway
80
What is the role of the enzyme PTEN?
Dephoshorylates PIP3 to PIP2 Reverse of effect of PI-3-kinase Tumour suppressor gene
81
What is the role of PIP3?
Activates AKT kinases Inhibits apoptosis Acts on BAD
82
What is the TGF-beta pathway?
Growth inhibitory pathway for epithelial cells Signal via transmembrane receptor to SMAD family Mutations in TGFbetaRII, SMAD4 or SMAD2 lead to cancer Tumour suppressors
83
In which cells can leukaemias arise?
1. Fully differentiated lymphocytes | 2. Stem cells
84
How does acute leukaemia develop?
From myeloid/lymphoid precursors Differentiation is blocked More aggressive
85
How does chronic leukaemia develop?
From differentiated myeloid/lymphoid cells Shows differentiation Less aggressive
86
What is myeloma?
Cancer of fully differentiated B cells
87
How is proliferation limited in lymph nodes?
Apoptosis balances proliferation during somatic mutation in the germinal centre of the lymph node
88
What is BAX?
Major mediator of apoptosis Upregulated by p53 Antagonises Bcl2 Mediates permeabilisation of mitochondrial membrane and activation of caspases
89
What is senescence?
Cell cycle arrest after a fixed number of cell divisions Hayflick's limit Escaped by tumour cells
90
What controls Hayflick's limit?
Telomere length
91
What are telomeres?
Repeat structures at the ends of chromosomes - TTAGGG Loop Shortened at each cell division
92
What is telomerase?
Reverse transcriptase enzyme that restores telomeres in the germ line Copies RNA template Turned on in most cancers
93
How is telomerase activated in tumours?
1. Point mutations in promoter | 2. Translocated next to strong promoter following chromosome rearrangement
94
Give some examples of signals that cause cell stress responses
1. Shortening of telomeres 2. DNA damage 3. Strong activation of oncogenes
95
What is oncogene-induced senescence?
Cells with activated oncogenes become senescent
96
How are stress responses alleviated?
1. Mutation of p53 | 2. Mutation of RB1
97
How do viruses overcome senescence?
Produce proteins that bind and inactivate p53 and RB1 Eg. HPV that causes cervical cancer
98
How does metastasis occur?
1. Escape of cells into vessels 2. Survival in circulation 3. Escape out of vessels 4. Survival and growth of new tumour
99
What is the major barrier to metastasis?
Survival and growth at distant site Very inefficient
100
What is angiogenesis?
Sprouting of new blood vessels to provide blood supply to tumour
101
Give two factors that control transcription
1. Transcription factors | 2. Chromatin modifiers
102
What is MYC?
Oncogene Transcription factor Powerfully upregulates genes involved in proliferation
103
What is ERG?
Transcription factor Controls proliferation
104
What are chromatin modifiers?
Proteins that modify histones to turn genes on or off
105
What is MLL?
Histone methylase
106
What occurs to E-adhesin in breast cancer?
It is inactivated
107
Which TCA enzymes are notably mutated in cancer?
Isocitrate dehydrogenase 1 Mutated in glioblastoma and leukaemia May interfere indirectly with DNA methylation
108
What is chromosome translocation?
Pieces of two different chromosomes are joined to each other following breakage of DNA or an accident during DNA replication
109
What are indels?
Small insert or deletion Usually results in frameshifting
110
What is Ras?
G-protein Activated by GTP-binding and inactivated by hydrolysis of GTP to GDP Mutations block hydrolysis Some mutations block access to GTPase to active site
111
In which cancers is BRAF notably mutated?
1. Melanoma | 2. Colorectal carcinoma
112
What is the commonest BRAF mutation?
Val to glu at position 600 Adjacent to activating phosphorylation site Negative charge of glu mimics phosphorylation so causes activation
113
In which cancers is PI3K catalytic subunit notably mutated?
Breast cancers
114
What is a gene fusion?
Joining two genes together to create a new gene Potentially the most powerful kind of cancer mutation
115
Which gene fusion is associated with chronic myeoloid leukaemia?
BCR-ABL Philadelphia chromosome Chromosomes 9 and 22
116
What is the effect of the BCR-ABL gene fusion?
ABL is a tyrosine kinase N terminus of BCR forms dimers and replaces regulatory N terminus of ABL, activating ABL BCR has stronger promoter than ABL
117
In which stage of mitosis are cells arrested for karyotyping?
Metaphase
118
Which fusion gene is found in 50% of prostate cancers?
TMPRSS2-ERG Formed by deletion between these two genes
119
What is amplification?
Cell acquires large numbers of an oncogene after repeated duplication of a segment of the genome
120
Give some examples of amplified genes
1. Cyclin D1 | 2. ERBB2/HER2
121
Which technique can be used to detect amplification?
FISH Fluorescence in-situ hybridisation
122
Which genes are inactivated by genome modification?
1. MLH1 (mismatch repair) | 2. E-cadherin (cell adhesion)
123
What is Bcl2?
Oncogene Anti-apoptosis protein Upregulated by chromosome translocation in some lymphomas
124
What is BRAF?
Oncogene Downstream of Ras Found mutated in melanomas Activated by gene fusion
125
What is cyclin D1?
Oncogene Controls Rb1 with CDK4 Activated by amplification in breast cancer
126
What is the ERBB family of receptors?
Family of receptor tyrosine kinases Includes EGFR and HER2 HER2 is target for herceptin
127
What is ERG?
Oncogene Transcription factor Involved in gene fusions in prostate cancer
128
What is MLL?
Oncogene Histone methyl transferase Modifies histones Fused by translocation in leukaemias
129
What is the MYC family?
Oncogenes Family of transcription factors Highly amplified
130
What is PI3CA?
Catalytic subunit of PI3 kinase Mutated in breast and colorectal cancers
131
What is the Ras family?
Oncogenes G proteins that carry signals from growth factors to nucleus Activate MAPkinase pathway
132
What are TCF3 and TCF4?
Oncogenes Downstream of Wnt pathway Gene fusions occur in colon cancer
133
What is APC?
Tumour suppressor gene Large cytoplasmic protein that interacts with beta-catenin Inactivated in most colon carcinomas
134
What is BRCA1?
Tumour suppressor gene Component of DNA repair Mutation associated with hereditary breast cancers
135
What is BRCA2?
Tumour suppressor gene Component of homologous recombination repair Mutation associated with hereditary breast cancers
136
What is INK4A/p16?
Tumour suppressor genes Inhibitors of CDKs Often deleted
137
What are MLH1 and MSH2?
Recognition proteins of mismatch repair complex Mutation in some colon cancers
138
What is p53?
Nuclear protein that arrests cell cycle in cases of DNA damage and other insults
139
What is PTEN?
Phosphatase that antagonises PI3KCA
140
What is SMAD4?
Carries inhibitory signals in the TGF-beta signalling pathway Mutated in some colon cancers and other cancers
141
What is the TGF-beta family?
Inhibitory growth factors that regulate the differentiation of cells
142
What are mutagens?
Agents that directly damage DNA Eg. chemicals and radiation
143
What are promoters?
Non-mutagenic agents that increase the effects of mutagens
144
What is the best known promoter?
TPA
145
What is aflatoxin?
Most potent mutagenic carcinogen
146
What is TPA?
Promoter Comes from seeds of tropical plant Croton tiglium Mimics DAG, agonist for PKC
147
What is a risk factor for breast cancer?
Risk proportional to interval between menarche and first pregnancy for childbearing women
148
What are the causes of cancer?
1. Mutagens 2. Promoters 3. Tumour viruses and other infections 4. Chronic irritation 5. Spontaneous error
149
What is the principal effect of UV radiation?
Photoactivation of pyrimidine residues Form dimers where two thymines or one thymine and one cytosine occur sequentially Disrupts base pairing
150
How is UV damage repaired?
Base excision repair
151
Which condition is at particular risk from UV damage?
Xeroderma pigmentosa Lack base excision repair machinery
152
How are carcinogens activated in the body?
By metabolism Enzymes that detoxify lipid-solube molecules for excretion by the body
153
How is β – napthylamine activated?
Hydroxylation
154
How is β – napthylamine made harmless?
Made soluble Conjugated with glucuronic acid
155
Where does β – napthylamine act?
Bladder tissue in man Where glucuronic acid conjugate is removed by glucuronidase Only a carcinogen in species that express glucuronidase in the bladder
156
Where does aflatoxin come from?
Produced by Aspergillus flavus Grows on peanuts in warm, humid conditions
157
What are aristolochic acids?
From aristolochia plant Carcinogens Cause kidney toxicity and kidney and liver cancer
158
What is the effect of asbestos inhalation?
Small fibres penetrate deep into lung Cause chronic inflammation and affect cell turnover Cause mesothelioma in lining of pleural cavity
159
What is ionising radiation?
1. X-rays 2. γ rays 3. β particles 4. α particles
160
How does ionising radiation damage DNA?
Produces free radicals and ions as it passes through tissue These are highly reactive and subsequently alter the structure of bases or cause strand breaks
161
What kind of damage do alpha particles cause?
Double strand breaks Multiple chemical changes Due to larger size
162
What kind of damage do gamma rays cause?
Leave scattered ions and radicals Only damage one residue on one strand of DNA molecule Usually repairable
163
How do infections cause cancer?
1. Viruses bring oncogenes into genome | 2. Chronic inflammation
164
How does HPV cause cancer?
Produces E6 and E7 proteins Inactivate p53 and Rb1
165
Which virus causes cervical cancer?
High risk HPV
166
Which virus causes nasopharyngeal carcinoma and Burkitt's lymphoma?
Epstein-Barr virus
167
Which virus causes hepatocellular carcinoma?
Hepatitis B virus
168
Which virus causes Kaposi's sarcoma?
Human herpesvirus 8
169
Which virus causes T-cell leukaemia and lymphoma?
Human T-cell lymph trophic virus type 1 (HTLV1)
170
What is HTLV1?
T-cell tropic retrovirus
171
What kind of cancer is associated with schistosome infection?
Bladder
172
What kind of cancer is associated with H. pylori infection?
1. Gastric adenocarcinoma | 2. MALT lymphoma
173
When do promoter molecules cause cancer?
After exposure to initiator mutagen, not before

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