Little enthusiasm was originally shown for research in apoptosis, but as the central role of apoptosis became more and more evident in normal tissue development and in the onset of certain diseases, interest grew to the point where today apoptosis research is one of the most competitive areas of biology. Research on apoptosis has caused a fundamental shift in how biologists and oncologists view the onset of cancer. At one time cancer could be explained as the dysregulation of cell growth as cells no longer remain growth arrested but entered the cell cycle to grow and divide uncontrollably. Now, in some cases, cancer can be described as the dysregulation of cell death in that cells, possibly injured or mutated, that should have died do not. This survival advantage likely allows these cells to accumulate mutations that result in a malignant phenotype.
Apoptosis also occurs spontaneously in many tumors.
Why apoptosis should occur in tumor cells is unknown, but there are a number of possible explanations. The apoptosis seen may simply be the tumor cell following the same programmed response of the normal cell from which it is derived, or it may be responding to stimuli produced in the tumor microenvironment. Small alterations in the rate of cell loss may, therefore, shift the balance in tumor physiology from growth to regression. Oncologists and basic scientists are pursuing this notion. Growth factors, cytokines, and a number of newly cloned genes have also been shown to have a considerable role in the instigation or repression of apoptotic signaling.