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Principles of Disease > Genetic Predisposition to Cancer > Flashcards

Genetic Predisposition to Cancer Flashcards

1
Q

What is cancer a disease of?

A

Somatic cells

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2
Q

Where do inherited cancer syndromes arise from?

A

Mutations in the germline cells

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3
Q

What are the genetic processes involved in the clonal expansion of tumours?

A

Oncogenes
Tumour supressor genes
DNA damage-response genes

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4
Q

How do oncogenes work?

A

Proto-oncogenes are normal genes that code for proteins to regulate cellular growth and differentiation. Mutations can change a proto-oncogene into an oncogene, which accelerates cell division- cancer arises when these oncogenes are activated.

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5
Q

Are oncogenes recessive or dominant?

A

Dominant

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6
Q

How do tumour suppressor genes work?

A

These are the cellular brakes for cell growth- the genes inhibit the cell cycle or promote apoptosis, or both. Cancer arises when both brakes fail- this is reffered to as the 2-hit hypothesis.

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7
Q

Are tumour suppressor genes recessive or dominant?

A

Recessive

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8
Q

How do DNA damage-response genes work?

A

These are the repair mechanics for DNA- cancer arises when both genes fail, spreading the accumulation of mutations in other critical genes.
(HNPCC results from failure of mismatch repair genes, MMI corrects errors).

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9
Q

What do MMR do?

A

MMR (mismatch repair genes) correct errors that spontaneously occur during DNA replication like single base mismatches or short insertions and deletions.

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10
Q

How does MSI show disfunction in MMR?

A
  • Cells with abnormally functioning MMR tend to accumulate errors.
  • Microsatellites (aka Simple Sequence Repeats SSR) are repeated sequences of DNA, can be made of repeating units of 1 – 6 base pairs
  • MSI (changes in microsatellite sequences) is the phenotypic evidence that MMR is not functioning normally – genetic hypermutability.
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11
Q

Describe a benign tumour.

A

Benign- lacks ability to metastasise, rarely becomes cancerous, can still cause health effects due to localized pressure on organs.

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12
Q

Describe a dysplastic tumour.

A

Dysplastic- benign but could progress into malignancy, cells show abnormalities in appearance and cell maturation, sometimes referred to as pre-malignant.

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13
Q

Describe a malignant tumour.

A

Malignant- Metastasises, not benign, spreads throughout body.

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14
Q

How are inherited cancer syndromes spotted in examination?

A

Family history

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15
Q

What are de novo mutations?

A

New mutations in germline cell of parent, no family history of hereditary cancer syndrome.

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16
Q

What are most inherited cancer genes like?

A

Most cancer susceptibility genes are dominant with incomplete penetrance- they often appear to skip generations and individuals inherit the cancer susceptibility gene, not the cancer.

17
Q

What are the forms of retinoblastoma?

A

Inherited/non-inherited, paediatric diagnosis

18
Q

What are the risk factors for breast cancer?

A

Ageing, family history, diet (alcohol), lack of expertise. There are high and moderate risk genes.

19
Q

What cancers are associated with the BRCA1 gene?

A

Lifetime risk of breast cancer, second primary breast cancer, and ovarian cancer. Also additional risk of colon and prostate cancer.

20
Q

What cancers are associated with the BRCA2 gene?

A

Lifetime risk of breast cancer, male breast cancer and ovarian cancer. Additional risk of prostate, pancreatic and laryngeal cancers.

21
Q

What are the risk factors for colorectal cancer?

A

Risk factors include ageing, previous history of CRC or adenomas, high-fat/low-fibre diet, inflammatory bowel disease, family history.

22
Q

Describe the pathway of adenoma to carcinoma formation.

A

Normal epithelium > Hyperproliferative epithelium > Adenoma > Carcinoma

23
Q

What are the hereditary CRC syndromes?

A

Non-polyposis
• Few to no adenomas
Polyposis
• Multiple adenomas- FAP/AFAP/MAP

24
Q

What are the clinical features of HRPCC?

A

Early but variable age at CRC diagnosis, tumour site throughout colon rather than descending colon, extracolonic cancers including endometrium, ovary, urinary tract, small bowel, bile ducts, sebaceous skin tumours.

25
Q

What are the clinical features of FAP?

A

Estimated penetrance for adenomas >90%
Risk of extracolonic tumors (upper GI, desmoid, osteoma, thyroid, brain, other)
CHRPE may be present
Untreated polyposis leads to 100% risk of cancer. Attenuated = later onset

26
Q

What distinguishes attenuated FAP?

A

Later onset

27
Q

What is recessive MYH polyposis distinguished by?

A

Similar clinical features of FAP.

28
Q

What can multiple gene mutations of lower risk explain?

A
  • May explain families with history of cancer and no identified mutation
  • May explain differences in cancer penetrance in families with same mutation
29
Q

How are these inherited cancer syndromes controlled?

A

Surveillance
Surgery
Prophylactic Chemoprevention

Principles of Disease (22 decks)

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