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PoD > Genes: Cancer > Flashcards

Genes: Cancer Flashcards

1
Q

First thing to consider with cancer

A
  • family history
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2
Q

Non-heritable vs heritable

A

Non-heritable: most cancers, somatic mutation, occurs in non-germline tissues
Heritable: Germline mutation, present in egg or sperm, causes family cancer syndromes, affects every cell in offspring

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3
Q

Genetic processes associated with cancer:

A
  • Oncogenes
  • Tumour suppressor genes
  • DNA damage-response for DNA
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4
Q

Oncogenes

A

can accelerate cell division

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5
Q

Proto-oncogenes

A
  • Normal gene that codes for proteins to regulate cell growth and differentiation
  • A mutation can change proto-oncogene into an oncogene
  • > Cells get stuck in growth mode
  • An oncogene virus can active an oncogene e.g. HPV
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6
Q

Tumour suppressor genes

A
  • Cell’s brakes for cell growth
  • Genes inhibit cell cycle or promote apoptosis or both
  • Cancer arises when the genes cease to do this along with DNA damage response
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7
Q

Two-Hit Hypothesis

A
  • Inherit an autosomal dominant mutation, 1st hit isn’t enough but you are susceptible to cancer
  • 2nd hit by coincidence results in tumours -> leads to cancer
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8
Q

DNA damage-response genes

A
  • Repair mechanics for DNA. Spell checker
  • Cancer arises comes from tumour suppressor genes and DNA damage response fail
  • The result is an accumulation of mutations in other critical genes
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9
Q

Failure of mismatch repair genes

A
  • If there is a defective DNA repair then this can lead to microsatellite instability (MSI)
  • MSI is evidence of MMR nor working
  • These types of cells accumulate errors
  • Shows a predisposition for bowel cancer
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10
Q

Examples of oncogenes and syndrome

A
  • Genes: RET

- Syndrome: MEND2 (Multiple endocrine neoplasia)

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11
Q

Examples of tumour suppressor gene and syndrm

A
  • Genes: BRCA1, BRCA2, APC, RB

- Breast/ovarian cancer, FAP, retinoblastoma

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12
Q

Examples of DNA repair genes and syndromes

A
  • Genes: MLH1, MSH2, PMS1, PMS2

- Syndrome: HNPCC (Hereditary non-polyposis colon cancer)/Lynch syndrome

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13
Q

Other causes

A
  • Autosome recessive syndromes: MYH polyposis

- Multiple modifier genes of lower genetic risk

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14
Q

De Novo mutations

A
  • New mutation occurs in germ cell of parent, no family history
  • e.g. familial adenomatous polyposis (30% of cases), multiple endocrine neoplasia 2B
  • Hereditary retinoblastoma
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15
Q

Retinoblastoma

A
  • Most common eye tumour in children
  • Heritable and nonheritable forms
  • Identifying at-risk infants substantially reduces morbidity and mortality
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16
Q

Heritable retinoblastoma

A
  • Bilateral
  • 20% of cases
  • Increased risk of secondary primaries: osteosarcoma, other sarcomas, melanoma
17
Q

Nonheritable retinoblastoma

A
  • Unilateral

- No secondary primaries

18
Q

Risk factors for breast cancer

A
  • Ageing
  • FH (20-40% of hereditary cases)
  • Dietary factors
  • Lack of exercise
  • Early menarche/late menopause i.e. long exposure of breast tissues to hormones
  • Oestrogen use: pill and HRT
  • No kids/no breast feeding
19
Q

BRCA1 functions

A
  • Checkpoint mediator
  • DNA damage signalling and repair
  • Chromatin remodelling (inactive X chromosome)
  • Transcription
20
Q

BRCA1 associated cancers

A
  • Breast cancer: 50-85% (often early age at onset)
  • Second primary breast cancer: 40-60%
  • Ovarian cancer: 15-45%
21
Q

BRCA2 associated cancers

A
  • Breast: 50-85%
  • Ovarian: 10-20%
  • Male breast cancer: 6%
22
Q

Risk factors for colorectal cancer

A
  • Age
  • Personal history of CRC or adenomas (dysplastic polyps)
  • High fat, low-fibre diet
  • Inflammatory bowel disease
  • FH, failure of MMR
23
Q

Non-polyposis

A
  • Hereditary non-polyposis colon cancer: CRC or endometrial cancer
  • Early diagnosis: around 45
  • Tumour site is throughout rather than descending colon (site of sporadic cancer)
  • Extracolonic cancers: endometrium, ovary, stomach, urinary tract, small bowel etc
24
Q

Types of polyposis

A
  • Multiple adenomas
  • Familial adenomatous polyposis
  • Attenuated familial adenomatous polyposis
  • MYH associated polyposis
25
Q

FAP

A
  • severe colonic polyposis (with or without CRC)
  • 90% penetrance
  • risk of extracolonic tumours - upper GI, brain, thyroid
  • Untreated leads to 100% risk of cancer
  • Develop cancer by mid to late 30s
  • Congenital hypertropy of the retinal pigment eithelium (CHRPE), spot at back of ete
  • > 4 CHRPEs is a greater risk of FAP
26
Q

AFAP

A
  • less severe colonic polyposis (with or without CRC)
  • Later onset, around 50
  • No associated CHRPE
  • Few polyps but you do get upper GI polps
  • Associated with mutations at 5’ and 3’ ends of APC gene
27
Q

MAP

A
  • varying degree of severity (with or without CRC)
  • similar GI features to attenuated FAP
  • Recessive inheritance
28
Q

Management

A
  • Surveillance
  • Surgery
  • Chemoprevention: certain nonsteroidal anti-inflammatory drugs can slow polyp formation
  • HMPCC: adult carriers take aspirin and can significantly reduce risks
29
Q

Predictive gene tests:

A
  • Not always available
  • Problem with gene variants of unknown signficance
  • For adult onset cancers, predictive test not offered until adulthood
30
Q

Advances in predictive test

A
  • Exome sequencing

- Genome sequencing, still don’t know what to do with reults

PoD (33 decks)

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