Molecular Biology

Molecular Genetics

New View Of Cancer: 'Epigenetic' Changes Come Before Mutations

New View Of Cancer: 'Epigenetic' Changes Come Before Mutations: "Epigenetic changes -- those that don't affect the gene's sequence of DNA but change the gene in other ways -- influence a wide variety of human diseases, including cancer, birth defects and psychiatric conditions. Epigenetic alterations include the turning off or quieting of genes that normally suppress cancer and the turning on of oncogenes to produce proteins that set off malignant behavior.

Feinberg and his colleagues propose that cancers develop via a three-step process. First, there is an epigenetic disruption of progenitor cells within an organ or tissue, altered by abnormal regulation of tumor-progenitor genes. This leads to a population of cells ready to cause new growth.

The second step involves an initiating mutation within the population of epigenetically disrupted progenitor cells at the earliest stages of new cell growth, such as the rearrangement of chromosomes in the development of leukemia. This mutation normally has been considered the first step in cancer development.

The third step is genetic and epigenetic instability, which leads to increased tumor evolution.

Many of the properties of advanced tumors, including the ability to spread, or metastasize, are inherent properties of the progenitor cells that give rise to the primary tumor, Feinberg notes. These properties do not necessarily require other mutations to occur. "

. . . developing since 10/06/06