Proto-oncogenes activation mechanisms. Role of gene overexpression in breast cancer

The Proto-oncogenes play a key role in the regulation of cell proliferation and differentiation, together with tumor supressor, DNA repair and apoptosis regulatory genes. The accumulation of successive qualitative and/or quantitative alterations of these genes constitutes the basis of cancer development. The proto-oncogene overexpression is an important mechanism of oncogene activation since it represents a gain-of-function event and, therefore, the estimulation of cell proliferation or survival. Overexpression can be associated with genetic changes, as chromosome translocation or gene amplification, or with epigenetic changes, mainly DNA methylation and histone acetylation. This kind of alteration is frequent in breast cancer and associated with poor prognosis and resistance to the treatment.