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Death in normal and neoplastic cells

It is well known that cell loss occurs from growing neoplasms in vivo. This is particularly prominent in slowly growing tumours, including many human examples (Steel, 1967), and in some cases the rate of cell loss may be as much as 80% of the rate of cell production (Terz, Curutchet, and Lawrence, 1971). Whilst metastasis and desquamation may account for some of the observed cell loss much of it must be due to death of tumour cells in situ. Cell death on this scale, sufficient materially to influence the overall growth rate, has for years provoked enquiry but little is known of its mechanism. It is often regarded as a feature of abnormality, either in the environment within the tumour or in the neoplastic cells themselves, but the claim has also been made that it represents the retention by tumour cells of a basic physiological function concerned also with the control of normal cell populations (Laird, 1969). The problem is of more than academic interest, since relatively minor increases in the cell death rate, could they be induced without corresponding increases in cell production, would ensure regression of many human tumours. In an attempt to clarify some aspects of this problem, thispaper reviews the phenomenon of cell death in both normal and neoplastic populations.