DIFFERENT CHEMO-SENSITIVITY AND ENDOCRINO-SENSITIVITY OF MCF-7 CELLS WITH OR WITHOUT ESTRADIOL SUPPLEMENT IN-VITRO

The sensitivity of MCF-7 cells to tamoxifen (TAM) and mitomycin C (MMC ) was assessed in rapidly and slowly growing cells with or without est radiol supplementation, respectively. The growth of MCF-7 was inhibite d by MMC in a concentration-dependent manner with or without estradiol (E2) supplementation. Preincubation with MMC suppressed subsequent E2 stimulated growth of MCF-7. TAM inhibited the growth of MCF-7 supplem ented with E2, and preincubation with TAM prevented subsequent E2 stim ulated growth of MCF-7. However, TAM did not inhibit the growth of MCF -7 cells in E2free medium. These results suggested that MMC may be mor e effective than TAM on breast cancer cells in the dormant or slow-gro wth phase.