Cancer Flashcards
2 ways in which cancer is a genetic disease
- Caused by alterations of a gene or multiple genes that regulate the growth of a cell
- Some mutations are inherited in families, producing a genetic predisposition
Genetic cancer risk: Mendelian or complex trait?
Can be either Mendelian (ex- BRCA1) or complex
What makes cancer a multistage genetic process
Genetic alterations accumulate as cells transform into malignancy (normal -> pre-malignant -> malignant)
3 types of cancer genes
Oncogenes
Tumor suppressor genes
DNA repair genes
Oncogenes
Positive regulators of cell proliferation
Type of mutations that turn proto-oncogenes into oncogenes
Gain of function: one mutant allele has dominant effect over normal allele
Tumor suppressor genes
Cell cycle checkpoints
Types of mutations that alter tumor suppressor genes in cancer
Loss of function: both copies of allele have to be inactivated (recessive)
Types of mutations that alter DNA repair genes in cancer
Loss of function: both copies of allele have to be inactivated (recessive)
Consequences of DNA repair gene mutations
Increased mutations, leading to creation of oncogenes or destruction of tumor suppressor genes
Driver vs passenger mutations
Driver mutations cause cancer, but passenger mutations don’t
Passenger mutations can be used as lineage markers to track timeline of cancer
Examples of genes that frequently harbor driver mutations
p53 (tumor suppressor gene)
HER, EGF, PDGF (oncogenes: growth factors)
BRCA (tumor suppressor gene)
Helicase, MSH2, MLH1, XP A-G (DNA repair genes)
2-hit hypothesis in retinal blastoma
For inherited cases, one allele has a germline mutation (inherited) and the other is mutated in somatic cells
Causes earlier age of onset with multiple tumors or both eyes affected
Mutated gene in retinal blastoma and method of inheritance
RB (retinal blastoma) protein
Tumor suppressor gene
Dominant inheritance (but recessive at level of cell)
