Proliferation Kinetics of Density-inhibited Cultures of Human Cells, A Complex in Vitro Cell System1

Proliferation kinetics and cell cycle parameters have been measured in exponentially growing and density-inhibited (daily medium changes) stable-plateau phase cultures of Chang human liver (LICH) cells. The mean duration of all phases of the cell cycle among the cycling population was approximately doubled in density-inhibited cultures. About 50% of the population was effectively noncycling but still viable. The lower rate of proliferation was balanced by cell loss into the culture medium leading to a constant cell number and a cell turnover rate of 20% per day. Densityinhibited cultures of LICH cells possess a number of the kinetic characteristics of tumors in vivo and may provide a useful in vitro system for a study of the effects of some chemotherapeutic agents, protracted schedules of X-irradiation, and of interaction between the two.