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Mechanisms of Disease > Lecture 10 - Neoplasia III > Flashcards

Lecture 10 - Neoplasia III Flashcards

1
Q

what are 3 examples of inherited susceptibility to development of tumours?

A

retinitis pigmentosum
ataxia telangiectasia
fanconi’s anaemia

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2
Q

how does retinitis pigmentosum increase susceptibility to tumours?

A

increased risk of skin cancers when exposed to uv rays in sunlight

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3
Q

how does ataxia telangiectasia increase susceptibility to tumours?

A

defective response to radiation damage
profound susceptibility to lymphoid malignancies
usually die before 20

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4
Q

how does fanconi’s anaemia increase susceptibility to tumours?

A

sensitivity to dna cross linking agents, marrow hypo function and multiple congenital anomalies
predisposition to cancer

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5
Q

which gene inheritance causes familial adenomatous polyposis?

A

apc

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6
Q

which gene inheritance causes breast cancer?

A

brca 1/2

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7
Q

which gene inheritance causes li fraumeni syndrome?

A

p53

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8
Q

what is a proto oncogene?

A

a normal gene that can become an oncogene due to mutations or increased expression

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9
Q

what is the dna sequence of a proto oncogene?

A

identical to viral oncogenes

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10
Q

how do proto oncogenes become oncogenes?

A

mutation, amplification, translocation

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11
Q

what are the products of oncogenes?

A

oncoproteins

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12
Q

what is the significance of oncogenes?

A

cell can escape normal growth contro

lbecomes self sufficient - doesnt require external signals for growth

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13
Q

how many alleles of a proto oncogene need to mutate to cause neoplasia?

A

one

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14
Q

what is a tumour suppressor gene?

A

a gene that encodes proteins that suppress growth and therefore cancer

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15
Q

what is the result of loss or alteration of tumour suppressor genes?

A

loss of growth suppression

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16
Q

how many alleles of a tumour suppressor genes need to mutate to cause neoplasia?

A

two

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17
Q

list three oncogenes

A

rasc-mycher-2

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18
Q

what is the role of the ras oncogene?

A

normally transmits growth promoting signals to nucleus
mutant ras is permanently activated - continuous stimulation of cells
15-20% of all cancers
colon and lung cancer

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19
Q

what is the role of the c-myc oncogene?

A

binds to dna, stimulates synthesis
amplified –> neuroblastoma, breast cancer
translocation from 8 to 14 –> burkitts lymphoma

20
Q

what is the role of the her-2 oncogene?

A

encodes for a growth factor receptor
amplified
25% of breast cancers

21
Q

what is a competitive antagonist at the her-2 receptor?

A

herceptin

22
Q

list two tumour suppressor genes

A

pRb

p53

23
Q

what is the role of pRb?

A

passage beyond R checkpoint at G1/S boundary is governed by phosphorylation of pRb
defect in both alleles leads to cell escaping cell cycle control
retinoblastoma

24
Q

what is the role of p53?

A

approx 50% of tumour contains p53 mutations
gene encodes a nuclear protein which binds to and modulates expression of genes important for cell cycle arrest, dna repair and apoptosis

25
Q

describe the initiator stage of carcinogenesis

A
  1. exposure of cells to sufficient dose of initiator
  2. cell is altered, potentially capable of producing a tumour
  3. permanent dna damage
  4. irreversible and has memory
  5. effect modified by genetic factors
  6. initiation is not sufficient for tumour formation
26
Q

describe the promoter stage of carcinogenesis

A
  1. can induce tumours in initiated cells
  2. non tumourigenic on their own
  3. need exposure after initiation
  4. cellular changes are reversible if remove promoter
  5. enhance proliferations, especially in mutated cells and increase incidence of further mutations
27
Q

how does radiation contribute to tumour development?

A

dna damage:
single strand break
double strand break
base damage

28
Q

what is the effect of radiation dependent on?

A

quality of radiation

dose

29
Q

give two types of radiation

A

ionising

ultraviolet

30
Q

how do chemicals contribute to tumour development?

A

act directly

require metabolic conversion to an active form

31
Q

give three examples that contribute to tumour development

A

polycyclic aromatic hydrocarbons
aromatic amines
alkylating agents

32
Q

how do polycyclic aromatic hydrocarbons contribute to tumour development?

A

produced in combustion of tobacco and fossil fuel
hydroxylated to active form
lung cancer, bladder cancer, skin cancer

33
Q

how do aromatic amines contribute to tumour development?

A

hydroxylated in liver and conjugated with glucorinic acid
deconjugated to active form in urinary tract by urinary glucuronidase
active form sits in bladder –> bladder cancer
rubber and dye workers

34
Q

how do alkylating agents contribute to tumour development?

A

bind directly to dna

nitrogen mustard

35
Q

give three viruses that contribute to tumour development

A

hep b
epstein barr
human papilloma

36
Q

how does hep b contribute to tumour development?

A

associated with hepatocellular carcinoma
viral dna integrated into host cell genome
virus causes liver cell injury –> regenerative hyperplasia
increased cell division gives increased risk of genetic changes

37
Q

how does epstein barr contribute to tumour development?

A

implicated in pathogenesis of burkitts lymphoma, some hodgkins lymphoma and nasopharyngeal carcinoma
infects epithelial cells or oropharynx and B cells
viral genes dysregulate normal proliferative and survival signals
sets the stage for acquisition of mutations

38
Q

how does human papilloma contribute to tumour development?

A

hpv genes disrupt normal cell cycle

viral genes incorporated into host cell genome, driving proliferation

39
Q

give five other agents that contribute to tumour development

A 
asbestos
aflatoxins
schistosoma
helicobacter
hormones
40
Q

what does asbestos cause?

A

malignant mesothelioma

lung cancer

41
Q

what do aflatoxins cause?

A

hepatocellular carcinoma

42
Q

what does schistosoma cause?

A

bladder cancer

43
Q

what does helicobacter cause?

A

gastric cancer

lymphoma

44
Q

what do hormones cause?

A

androgens

hepatocellular carcinoma

45
Q

give three conditions that predispose tumours

A

ulcerative colitis
cirrhosis
adenoma of colon/rectum

Mechanisms of Disease (11 decks)

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