Apoptosis
The term apoptosis refers to the death of a cell according to a genetic programme. In the adult organism, diseased, old or useless cells are driven into "suicide" by a complex system of signals and messengers.
In cancer cells, the apoptosis programme is disturbed: the tumour cells do not react to the cell death signals and continue to divide without inhibition. A major reason for this is errors in the apoptosis signalling pathway or pathological changes in the apoptosis-triggering genes.