Cancer is a genetic disease.
The fundamental defect of cancer cells is a deregulated proliferation that results from the progressive accumulation of genetic and epigenetic alterations. The regulation of cell proliferation in multicellular organisms is complex and requires the integration of a multitude of signals, both extracelluar and intracellular. The genetic and epigenetic alterations in cancer cells invariably affect the regulatory pathways that govern the proper cellular responses to this myriad of signals. Normal proliferative cells are endowed with the abilities to choose between growth and quiescence, differentiation and apoptosis. The execution of these alternative choices is influenced by physiological factors and stress to achieve a controlled and balanced proliferation.