Improved coupling between proliferation‐arrest and differentiation‐induction in ML‐1 human myeloblastic leukemia cells

Abstract

Proliferation and differentiation are coupled in normal cells and are aberrant in leukemia cells. The studies reported here were aimed at more effectively coupling proliferation-arrest and differentiation-induction in a human myeloblastic leukemia cell line (ML-1). This was accomplished by using reduced serum conditions in conjunction with a differentiation-inducing agent: cells were first incubated in reduced serum [0.3% fetal bovine serum (FBS)] instead of standard conditions (7.5% FBS) and, second, exposed to 12-O-tetradecanoylphorbol-13-acetate (TPA). The effects of this protocol were as follows: first, cell proliferation was slowed and cells accumulated in G0/G1 phase of the cell cycle; this occurred with only a minimal decrease in viability [to approximately 88-92% (0.3% FBS) from greater than or equal to 96% (7.5% FBS)]. Second, the induction of differentiation was accelerated; this allowed the time of exposure to TPA to be decreased. Acceleration of induction was very pronounced when cells were maintained in 0.3% FBS both before and during exposure to TPA, with TPA at concentrations above the minimum sufficient for induction but below those causing significant cytotoxicity; as little as 1 hour of TPA exposure resulted in near-maximal induction (approximately 80%) with this protocol, compared to the greater than or equal to 1 day required with previous standard protocols. In sum, conditions that slow ML-1 cell proliferation (0.3% FBS) enhance TPA-induced differentiation, substantially narrowing the time frame of induction; these conditions should be useful for studying the molecular mechanisms that underlie the induction process.