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POD > Genetic Predisposition to Cancer > Flashcards

Genetic Predisposition to Cancer Flashcards

1
Q

What causes cancer?

A
  • chance
  • environmental factors
  • inherited predisposition
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2
Q

Somatic vs Germline mutations

A
  • Somatic mutations occur in non-germline tissues and are nonheritable.
  • Germline mutations are present in egg or sperm and are heritable. They cause cancer family syndromes.
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3
Q

What is a proto-oncogene?

A

Normal genes that code for proteins to regulate cell growth and differentiation

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4
Q

How does a proto-oncogene become an oncogene?

A

by mutation

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5
Q

What do oncogenes do?

A
  • accelerate cell division

- can cause cancer if stuck in ‘on’ mode

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6
Q

What are tumour suppressor genes?

A

Genes that inhibit the cell cycle or promote apoptosis. They act as the cell’s brakes for cell growth.

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7
Q

What are DNA damage-response genes?

A

the repair mechanics for DNA

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8
Q

How does cancer arise from DNA damage-response genes?

A

Cancer arises when both genes fail, speeding the accumulation of mutations in other critical genes

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9
Q

What does HNPCC result from?

A

Failure of mismatch repair (MMR) genes

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10
Q

What does failure of MMR lead to?

A

Microsatellite Instability (MSI)=addition of nucleotide repeats

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11
Q

What does MMR do?

A

MMR corrects errors that spontaneously occur during DNA replication like single base mismatches or short insertions and deletions.

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12
Q

What evidence is there that MMR is not functioning normally?

A

MSI is the phenotypic evidence

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13
Q

What happens to cells with abnormally function MMR?

A

Thy tend to accumulate errors as novel microsatellite fragments (simple sequence repeats, SSR) are created

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14
Q

What is an example of an autosomal recessive syndrome?

A

MYH polyposis

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15
Q

What are other causes of cancer?

A
  • autosomal recessive disorders

- multiple modifier genes of lower genetic risk

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16
Q

What is a De Novo mutation?

A

A new mutation which occurs in the germ cell of a parent. There is no family history of hereditary cancer syndrome.

17
Q

What are 3 conditions in which de novo mutations are common in?

A
  • Familial adenomatous polyposis
  • Multiple endocrine neoplasia 2B
  • Hereditary retinoblastoma
18
Q

What is retinoblastoma?

A

The most common eye tumour in children which occurs in heritable and nonheritable forms

19
Q

What are the risk factors involved in breast cancer? (8)

A
  • ageing
  • family history
  • early menarche
  • late menopause
  • nulliparity
  • estrogen use
  • dietary factors
  • lack of exercise
20
Q

What genes can cause hereditary susceptibility to breast cancer?

A
  • BRCA1
  • BRCA2
  • TP53
  • PTEN
  • Undiscovered genes
21
Q

What are the functions of the BRCA1 gene?

A
  • checkpoint mediator
  • DNA damage signalling and repair
  • chromatin remodelling (inactive X chromosome)
  • transcription (not essential for this)
22
Q

What is the function of the BRCA2 gene?

A

DNA repair by homologous recombination

23
Q

What are the associated cancers of BRCA1?

A
  • breast cancer
  • secondary breast cancer
  • ovarian cancer
  • possible increased risk of other cancers
24
Q

What are the associated cancers of BRCA2?

A
  • breast cancer
  • male breast cancer
  • ovarian cancer
  • increased risk of prostate, laryngeal and pancreatic cancers
25
Q

What are the risk factors associated with colorectal cancer?

A
  • ageing
  • personal history of CRC or adenomas
  • high fat, low fibre diet
  • inflammatory bowel disease
  • family history of CRC
26
Q

What syndromes are associated with CRC?

A
  • non-polyposis (few to no adenomas)

- polyposis (multiple adenomas)

27
Q

Give an example of a non-polyposis syndrome.

A

Hereditary non-polyposis colon cancer aka Lynch syndrome- CRC &/or endometrial cancer

28
Q

Give 3 example of polyposis syndromes.

A
  • Familial adenomatous polyposis- severe colonic polyposis
  • attenuated FAP- less severe colonic polyposis
  • MYH associated polyposis- varying degrees of colonic polyposis
29
Q

What are the clinical features of HNPCC?

A
  • early but variable age at CRC diagnosis
  • tumour site throughout colon
  • extra colonic cancers: endometrium, ovary, stomach, urinary tract, small bowel, bile ducts, sebaceous skin tumours
30
Q

What are the clinical features of FAP?

A
  • estimated penetrance for adenomas >90%
  • risk of extra colonic tumours (upper GI, desmoid, osteoma, thyroid, brain, othere)
  • CHRPE may be present (congenital hypertrophy of retinal pigment epithelium)
  • 100% risk of cancer if untreated
31
Q

What are the clinical features of AFAP?

A
  • later onset
  • few colonic adenomas
  • not associated with CHRPE
  • upper GI lesions
  • associated with mutations at 5’ and 3’ ends of APC gene
32
Q

What are the clinical features of MYH polyposis?

A
  • similar clinical GI features to AFAP
  • common mutations in mut-MYH gene
  • recessive inheritance
33
Q

What may multiple modifier genes of lower genetic risk explain?

A
  • families with history of cancer and no identified mutation

- differences in cancer penetrance in families with same mutation

34
Q

How can cancer risk in adenomatous polyposis syndromes be managed?

A
  • surveillance
  • surgery
  • chemoprevention

POD (54 decks)

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