Introduction to Cancer Genetics

Cancer is a general term, describing a group of different diseases. Because these diseases are different, it is unlikely that a general cure for cancer will evolve. Each type of cancer needs its own treatment program.

There are two common properties for all types of cancer:
1. Abnormal proliferation (so called neoplasia, that results in a neoplasm structure)
2. Invasive ability. Property that separates benign tumors from cancer.

Cancer cells invade other regions by travelling through the circulatory system or lymphatic system. This process is called metastasis, in which disease is spread from one organ to another non-adjacent organ.

Cancers can be classified according to cell type.

1.Leukemia and Lymphoma
2.Carcinoma
3.Sarcoma
4.Melanoma
5.Retinoblastoma, Neuroblastoma, Glioblastoma
(1: blood-borne cancers, 2-5: solid tumors)

Cancer is a genetic disease and can also be seen as a disturbance in the cell cycle regulation system. You can inherit a predisposition for cancer, but for the disease to break out additional somatic mutations are required.

These mutations arise from:
1. Environmental mutagens (physical or chemical agents that change DNA)
2. Imperfections during DNA copying and repair (so called spontaneous mutations).

There are two ways to categorize mutated genes based on function:

1.Function in a cancer cell
- Genes that have been activated or over expressed = oncogenes (one mutated allele is enough)
- Genes that have been inactivated:

1.Tumor suppressor genes. Both alleles need to be mutated. E.g. RB1 and p53
2. DNA-mismatch repair genes
Both alleles need to be mutated.

2.Function in normal cell:
- Genes that directly control proliferation (controlling cell birth rate or death rate) = Gatekeepers
- Genes that control the rate of mutation = Caretakers

Mutation in some genes always leads to the same type of cancer, independent of what kind of mutation or where it has arisen (e.g.WT1). Mutations in other genes result in many different forms of cancer (e.g. p53)