Oncogenes

Oncogenes are gain-of-function mutations of normal normal regulatory genes or photo-oncogenes. Originally discovered in retroviruses initiating a vari ety of animal and avian cancers, oncogenes nle believed to be important con tributors to human carcinogenesis. Photo-oncogenes are altered by point mut ation, amplification or. rearrangement. Structural alteration of proto-onco genes leads to a quantitative ol qualitative expression change of the corre sponding protein product. Oncoproteins subvert signal transduction pathways at the cell surface, in the cytosol and/or in the nucleus. Together with o ther oncoproteins or in the absence of tumor suppressor gene products, onco genes contribute to human cancer formation by supporting accelerated prolif eration, de-regulating cell cycle control or blocking apoptosis.