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Principles of Disease-Megan > Genetic Predisposition to cancer > Flashcards

Genetic Predisposition to cancer Flashcards

1
Q

Where do somatic mutations occur

A

In non-germline tissues so are non-heritable

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2
Q

Where are germline mutations found

A

In eggs or sperm so they are heritable and can cause cancer family syndromes

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3
Q

Which genetic processes are associated with cancer

A

Oncogenes
Tumour suppressor genes
DNA damage-response genes

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4
Q

What are tumours considered to be

A

Clonal expansions

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5
Q

What are proto-oncogenes

A

A normal gene that codes for proteins to regulate cell growth and differentiation

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6
Q

What can cause a proto-oncogene to become an oncogene

A

Mutations

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7
Q

What does one mutation in an oncogene do

A

Accelerate cell division

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8
Q

What are tumour suppressor genes

A

The cell’s brakes for cell growth

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9
Q

What are benign tumours

A

Tumours which are unable to metastasise

They rarely or never become cancerous but can still cause negative health effects due to pressure on other organs

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10
Q

What are the risk factors for breast cancer

A 
Nulliparity
Estrogen use
Dietary factors (e.g. alcohol)
Lack of exercise
Ageing
Family history
Early menarche
Late menopause
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11
Q

Which genes can cause hereditary cancer

A

BRCA1
BRCA2
TP53
PTEN

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12
Q

What are the risk factors of colorectal cancer

A 
Ageing
Personal history of CRC or adenomas
High-fat, low-fibre diet
Inflammatory bowel disease
Family history of CRC
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13
Q

What are adenomas seen as in colorectal cancer

A

Dysplastic

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14
Q

Which genes are associated with cancer

A

Oncogenes
Tumour suppressor genes
DNA damage-response genes

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15
Q

How many mutations are required in an oncogene for cancer development

A

1

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16
Q

How do tumour supressor genes act as a cell’s brakes

A

They inhibt the cell cycle or promote apoptosis or both

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17
Q

When does cancer arise in regards to tumour supressor genes

A

When BOTH breaks fail

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18
Q

How many mutations are required in tumour supressor genes for cancer development

A

2

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19
Q

What are DNA damage response genes

A

The repair mechanics for DNA

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20
Q

How many mutations are required in DNA damage response genes for cancer development

A

2

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21
Q

What happens when both genes fail in DNA damage response genes

A

It speeds the accumulation of mutations in other critical genes

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22
Q

What is HNPCC

A

Hereditary nonpolyposis colorectal cancer

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23
Q

How does HNPCC arise

A

From the failure of mismatch repair (MMR) genes

So a base pair mismatch will not undergo DNA repair causing another base to be inserted (so 2 wrong bases present)

24
Q

What does mismatch repair failure lead to

A

Microsatellite instability (MSI)

25
Q

What occurs in microsatellite instability (MSI)

A

Novel Microsatellite fragments (simple sequence repeats - SSRs) are created

26
Q

What do mismatch repair (MMR) genes do

A

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

27
Q

What is phenotypic evidence that MMR is not functioning normally

A

The presence of MSI

28
Q

What are dysplastic cells

A

Cells that show abnormalities of appearance & cell maturation
The are benign but could progress to malignancy so are known as pre-malignat

29
Q

What are malignant tumours

A

Tumours which can metastasise

30
Q

Give an example of an oncogene

A

RET

31
Q

Give an example of a cancer syndrome an oncogene can cause

A

MEN2 (Multiple endocrine neoplasia)

Familial medullary thyroid cancer

32
Q

Give an example of a tumour suppressor gene

A

BRCA1, BRCA2
APC
P53
RB

33
Q

Give an example of a cancer syndrome a tumour suppressor gene can cause

A

Breast/ovarian cancer
Li-Fraumeni syndrome
Retinoblastoma

34
Q

Give an example of a DNA repair gene

A

MLH1, MSH2, MSH6, PMS1, PMS2

35
Q

Give an example of a cancer syndrome a DNA repair gene can cause

A

HNPCC

Lynch Syndrome

36
Q

What are the other causes of cancer

A

Autosomal recessive syndromes (e.g. MYH polyposis)

37
Q

Where do de novo mutations occur

A

In the germ cell of a parent that has no family history of hereditary cancer syndrome

38
Q

Where are de novo mutations common

A

Familial adenomatous polyposis
Multiple endocrine neoplasia 2B
Hereditary retinoblastoma

39
Q

Why do most cancer susceptibility genes , which are dominant show incomplete penetrance

A

The individuals inherit altered cancer susceptibility gene not cancer

40
Q

What is retinoblastoma

A

The most common eye tumor in children that can occur in heritable and nonheritable forms
Identifying at-risk infants substantially reduces morbidity and mortality

41
Q

Describe the features of inherited retinoblastoma

A

Tumour: Usually bilateral
Average age at diagnosis: Under
Increased risk of second primaries: Osteosarcoma, other sarcomas, melanoma, others

42
Q

How many mutations are required for colorectal cancer to occur

A

Multiple

43
Q

How many adenomas occur in non-polyposis hereditary CRC syndromes

A

few to none

44
Q

How many adenomas occur in polyposis hereditary CRC syndromes

A

Multiple

45
Q

Give examples of polyposis hereditary CRC syndromes

A

FAP – severe colonic polyposis +/- CRC
AFAP - less severe colonic polyposis +/-CRC
MAP – varying degrees of colonic polyposis +/- CRC

46
Q

What is FAP, AFAP and MAP

A

FAP – familial adenomatous polyposis
AFAP – attenuated FAP
MAP – MYH associated polyposis

47
Q

What are the clinical features of HNPCC

A

Early but variable age at CRC diagnosis ( about 45 years)
Tumor site throughout colon rather than descending colon
Extracolonic cancers: ovary, stomach, urinary tract

48
Q

What are the clinical features of FAP

A

Risk of extracolonic tumors (upper GI, desmoid, osteoma, thyroid, brain, other)
CHRPE may be present

49
Q

What are the clinical features of FAP

A

Risk of extracolonic tumors (upper GI, desmoid, osteoma, thyroid, brain, other)
CHRPE (Congenital Hypertrophy of the Retinal Pigment Epithelium) may be present

50
Q

What are the clinical features of attenuated FAP

A 
Later onset (CRC about age 50)
Few colonic adenomas
Not associated with CHRPE
Upper GI lesions 
Associated with mutations at 5' and 3' ends of APC gene
51
Q

What are the clinical features of attenuated FAP

A 
Later onset (CRC about age 50)
Few colonic adenomas
Not associated with CHRPE
Upper GI lesions 
Associated with mutations at 5' and 3' ends of APC gene
52
Q

What are the meatures of MYH polyposis

A

Upper GI lesions (similar to attenuated FAP)
Common mutations in mut- MYH gene
Recessive inheritance

53
Q

How is cancer managed in adenomatous polyposis syndromes

A

Through:
Surveillance
Surgery
Chemoprevention

54
Q

Polymorphisms, mutations and variants of unknown significance may

A

Have no difference or have a huge difference

55
Q

What advances in technology are helping in cancer studies

A

Exome sequencing - looks for misprints in exons

Genome sequencing - looks for misprints in the whole genome

56
Q

What do inherited mutations cause

A

An increased predisposition to cancer

Only a small proportion of cancers are due to inherited mutations

Principles of Disease-Megan (41 decks)

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