Familial Cancer Flashcards
What are the main gene mutations that lead the cancer? (2)
- Caretaker genes
- Gatekeeper genes
What are the main categories of environmental factors that lead the cancer?
- Macro environment (e.g. chemicals, viruses)
- Micro environment (e.g. hormones, radicals)
What is the multistage process of colon carcinogenesis?
Normal epithelium >> hyperproliferative epithelium >> adenoma (early - intermediate - late) >> carcinoma >> metastasis
What is an inherited cancer?
Inherited genetic mutations increase an individual’s chance of developing cancer.
-e.g. BRCA
What is penetrance?
Percentage with a gene change who develop the condition.
-may be altered by genes/environment
What is the function of gatekeeper genes?
Directly regulate tumour growth.
- monitor / control cell division and death
- prevent accumulations of mutations
What is the main function of caretaker genes?
Improve genomic stability.
-e.g. repair mutations
What is the main function of landscaper genes?
Control the surrounding stromal environment.
Give an example of how importance of gene function affects the likelihood of developing cancer.
COLORECTAL CANCER:
- gatekeeper mutation (>95%)
- caretaker mutation (70%)
- landscaper mutation (10-20%)
What is the effect of loss of function of tumour suppressor genes?
Loss of function increases the risk of cancer.
Give some examples of tumour suppressor genes.
APC
BRCA
TP53
Rb
What is the function of oncogenes?
Regulate cell growth and differentiation.
How can oncogenes increase the risk of cancer?
Mutation»_space; gain of function»_space; increased risk of cancer.
What is Knudson’s 2 hit hypothesis?
Cancer is the result of multiple mutations.
- recessive at cellular level (i.e. need both genes inactivated)
- e.g. retinoblastoma
According the Knudson’s 2 hit hypothesis, what is the difference between sporadic and inherited cancers?
Sporadic - 2 ‘hits’ required in a cell.
Inherited - 1 additional ‘hit’ required in a cell (inherit 1).
What sort of inheritance pattern do most cancer syndromes show?
Autosomal dominant.
-for cancer RISK
How do autosomal recessive cancer syndromes account for some sporadic disease?
Must inherit both copies in order to have an increased cancer risk.
- appears to skip generations
- e.g. Fanconi anaemia
How many generations should be included when taking a family history?
At least 2 generations.
What are the main differences between sporadic and familial cancers?
SPORADIC
- onset at older age
- 1 cancer in individual
- family unaffected
FAMILIAL
- onset at younger age
- multiple 1* cancers in individual
- other family members affected
How is diagnostic and predictive testing usually used for cancer diagnosis?
DIAGNOSTIC - testing on DNA of relative with cancer to identify familial mutation
PREDICTIVE - if mutation is identified, test family for specific mutation to determine risk
What are some disadvantages of genetic testing in cancer?
- Anxiety
- May not lead to change in management
- Costly to NHS
What is retinoblastoma?
Rare childhood ocular cancer.
-classic example of 2-hit hypothesis
What gene is mutated in retinoblastoma?
Rb1 gene.
How does retinoblastoma develop?
Both Rb1 genes mutated/lost.
- inherited cases (1 mutation in germline) present at younger age
- bilateral cases are almost always germline
What is retinoblastoma associated with?
Increased risk of other cancers.
- due to radiation
- e.g. osteosarcoma
What is Familial Adenomatous Polyposis (FAP)?
Hundreds of polyps in bowel.
-high bowel cancer risk
How can FAP be inherited?
Autosomal dominant inheritance.
-APC tumour suppressor gene
What is the inheritance pattern of HNPCC?
Autosomal dominant inheritance.
- mismatch repair genes
- e.g. MLH1, MSH2, PMS 1
What is the Amsterdam criteria for HNPCC?
5 criteria used to identify HNPCC:
e.g. 2 affected generations, FAP excluded, tumours verifieds, etc
How is HNPCC managed?
Colonscopy every 2 years and removal of polyps.
- high cancer risk
What process are BRCA genes involved in?
DNA repair.
-autosomal dominant inheritance
What is the risk of breast cancer with BRCA gene?
80%.
What are the options for BRCA gene carriers?
- Breast screening
- Mastectomy
- Lifestyle changes
What mutation is associated with Li Fraumeni syndrome?
P53 mutation.
- autosomal dominant
- ~100% lifetime risk of cancer (e.g. breast, sarcoma)