Oncogenic signaling.

Cancer develops when one or more cells begin to grow uncontrollably, presumably as a result of alterations in the highly regulated processes of normal cell division. These changes may result from germline or somatic mutations in genes that control normal cell proliferation, resulting in oncogenes. Oncogenes--originally defined as viral genes that transformed mammalian host cells--code for proteins with diverse functions. Antioncogenes, or tumor-suppressor genes, code for proteins acting as brakes in the cell cycle. Mutations in or deletions of these genes release the brakes. An overview of cellular signaling pathways, how they may be altered in cancers, and recently reported clinical implications of abnormal expression of some oncogenes and tumor-suppressor genes will be presented here.