Proto-oncogenes are functional structural genes present in the human genome that have sequences very similar to oncogenes seen in viruses. Under normal conditions, the proto-oncogenes perform vital functions in the cell. They have been shown to be associated with control of cell growth, differentiation, and proliferation including regulation of secreted growth factors, cell surface receptors, signal transduction systems, transcription factors, and the cell cycle.

However, proto-oncogenes can be altered to an oncogenic form by mutation. This most commonly occurs by chromosomal rearrangement, usually a translocation, although point mutations and gene amplification have also been reported. Once transformed, or activated, the proto-oncogene loses its normal function causing a disruption in cell regulation patterns, and potentially leading to carcinogenesis. Each proto-oncogene appears to have a unique mutation that causes this change in state, i.e., every time a particular proto-oncogene is modified to the oncogenic form, the same mutation must...