BSC 219

Cancer Genetics

11/15/12

23.1 Cancer Is a Group of Diseases Characterized by Cell Proliferation

Tumor Formation: A Distinct Mass of Abnormal Cells

Benign tumor: the tumor remains localized.

Malignant tumor: tumor cells invade other tissues.

Metastasis: the tumor cells induce secondary tumors.

Cancer as a Genetic Disease

The clonal evolution of tumors

The tumor cells acquire more mutations that allow them to become increasingly more aggressive in their proliferate properties.

Role of Environmental Factors in Cancer

23.2 Mutations in a Number of Different Types of Genes Contribute to Cancer

Oncogenes and Tumor-Suppressor Genes

Oncogene: dominant-acting stimulatory genes that cause cancer

Proto-oncogenes: responsible for basic cellular functions in normal cells; when mutated, they become oncogenes.

Tumor-Suppressor Genes

Inhibit cancer and recessive acting; when mutated, normal cells become cancerous.

Genes That Control the Cycle of Cell Division

Signal-transduction pathways

A cascade of intracellular reactions

DNA repair genes

Genes that regulate telomerase

Inappropriate activation of telomerase may lead to cancer.

Genes that promote vascularization and the spread of tumors

23.3 Changes in Chromosome Number and Structure Are Often Associated with Cancer

Example:

A reciprocal translocation between chromosome 9 and 22 causes chronic myelogenous leukemia.

23.4 Viruses Are Associated with Some Cancers

Retroviruses cause cancer by

mutating and rearranging proto-oncogenes

inserting strong promoters near proto-oncogenes

Other viruses such as HPV produce cell growth factors

23.5 Changes in DNA Methylation Are Often Associated with Cancer

Epigenetic process:

Reversible genetic alterations

23.6 Colorectal Cancer Arises Through the Sequential Mutation of a Number of Genes