PROLIFERATION KINETICS OF A HUMAN BREAST-CANCER LINE INVITRO FOLLOWING TREATMENT WITH 17-BETA-ESTRADIOL AND 1-BETA-D-ARABINOFURANOSYLCYTOSINE

Abstract

The effect of 17.beta.-estradiol on an estrogen receptor-positive human breast cancer cell line (MCF-7) was studied. Low concentrations (10-9 M) of 17.beta.-estradiol enhanced the rate of cell proliferation; the overall cell cycle time was shortened; and the proportion of cells in the S phase increased. Higher concentrations (10-7 M) suppressed proliferation and slightly decreased the proportion of cells in DNA synthesis. When combined with 1-.beta.-D-arabinofuranosylcytosine, an S-phase-specific chemotherapeutic agent, 10-9 M 17.beta.-estradiol enhanced cell killing. This enhancement was not observed with 10-7 M. 17.beta.-estradiol. Kinetic changes caused by hormones have profound implications in clinical therapy, since the efficacy of cycle active agents may be altered.