Module Three: Cancer Genetics Flashcards
What is the multi-step model of cancer development?
The accumulation of genetic and epigenetic alterations resulting from the:
Activation of oncogenes resulting in excessive growth signals
Inactivation of tumour suppressor genes resulting in the removal of normal control
What is knudson’s two hit hypothesis?
Tumour suppressor genes act recessively i.e. Both copies of genes must be inactivated for growth control to be lost
What are the genes that are responsible for many familial cancers?
Rb, tp53, p16, BRAC1/2, APC, hMLH1
What are the limitations of gene therapy for cancer treatment?
Targeted delivery, expression, multiple TSG defects
What does the Rb code for?
Codes for a nuclear protein that is a major inhibitor of the cell cycle
Sporadic Rb1 gene mutations are found in what cancers?
Bone, lung and breast (and retinoblastoma)
What does the adenomatous polyposis coli gene have critical roles in?
Cell division and adhesion, regulates beta-catenin activity and the Wnt pathway
Germline mutations in APC are responsible for what syndrome?
Familial polyposis syndrome affecting the large bowl
95% of APC mutations cause what?
Frame shifts that lead to production of a truncated, inactive protein
What do the BRCA1 and 2 genes code for?
Codes for the proteins involved in the repair of damaged DNA
What inactivates BRCA1 in sporadic breast cancers?
Methylation
What genes encode for proteins that repair DNA mismatches arising during cell replication?
MLH1, MSH2, MSH6, PMS2
Inactivation of mismatch repair genes results in what?
Micro satellite instability
Germline mutations are responsible for?
Lynch syndrome
TP53 functions in:
Cell cycle arrest, DNA repair and apoptosis
What syndrome is a result of TP53 germ line mutations?
Li-Fraumeni Syndrome
Apart from mutation and chromosomal loss, TP53 can occur by what?
Binding to viral proteins
What viruses bind to TP53?
SV40, papilloma, Adenovirus
What can inhibit the activity of TP53 through feedback mechanism?
MDM2
How many regions does the central part of TP53 contain?
5
TP53 is a what?
Nuclear phosphoprotein
What are examples of low risk genetic factors?
Genes involved in carcinogen breakdown, DNA Repair
What cancers are associated with Lynch syndrome?dw
Colorectal, endometrial, rarer: gastric, renal
What are the five steps to genetic testing?
Step one: is a familial cancer syndrome likely based on the analysis of pedigree?
Step two: is there a family member who has had cancer and is willing to have genetic testing to find the specific mutation?
Step three: genetic testing => is a mutation detected in a known familial cancer syndrome gene?
Step 4: predictive testing is offered to other family members (with appropriate counselling)
Step 5: negative result: close surveillance not necessary
Positive: screening, prevention, surgery
Role of familial cancer clinics?
Risk assessment
Genetic testing
Counselling
Surveillance advice