CONCEPTS OF CELL-DEATH AND APPLICATION TO CARCINOGENESIS

The occurrence of cell death as a physiologic event in multicellular o rganisms has been known for more than 150 yr. In 1972, the term apopto sis was introduced on morphological grounds. The hypothesis that all k inds of cell death can be categorized as either ''apoptotic'' or ''nec rotic'' is not generally confirmed. Cells seem to use different pathwa ys for suicide, as reflected by different morphology: condensation-pro minent, Type I or apoptosis; autophagy-prominent, Type II; and so fort h. Type II cell death was found in mammary tissue and mammary tumor ce lls and in a variety of other organs. For unequivocal identification o f the various types of cell death, morphological, biochemical, and fun ctional criteria may be used in combination. During tumor development in various organs of animals and humans, not only rates of cell prolif eration but also rates of cell death may increase with increasing mali gnancy. Morphological and functional criteria (antipromotion, withdraw al of survival factors) indicate that cell death in tumors frequently is of an active nature.