3,3'-DIINDOLYLMETHANE INDUCES APOPTOSIS IN HUMAN CANCER-CELLS

3,3'-Diindolylmethane is a dimer of indole-3-carbinol formed both in v ivo and in vitro. In this study, human cancer cells MCF-7 (with wild-t ype p53), T47-D (mutant p53), and Saos-2 (deficient in p53 gene), were used to examine the anticancer activities of 3,3'-diindolylmethane. T he dose-dependent growth inhibitory effect was found in all these cell lines. Exposure of the cells to 50 mu M solution of 3,3'-diindolylmet hane for 48 h, apoptosis (programmed cell death) was evidenced by the characteristic morphology of cell nuclei under fluorescence microscope and the DNA ''ladder'' in agarose gel electrophoresis. The percentage of apoptotic cells in each cell line was found to be 12% for MCF-7, 1 4% for T47D and 13% for Saos2 cells. Exposure of MCF-7 cells to 100 mu M 3,3'-diindolylmethane for 24 h, 19% of apoptotic cells were detecte d by flow cytometry analysis. The lowest dose required for induction o f apoptosis in MCF-7 cells was found to be 10 mu M after 72 h incubati on. Western blot showed that wild-type p53 protein was unchanged after MCF-7 cells had been exposed to 50 mu M 3,3'-diindolylmethane for 8 h . This study provides evidences that 3,3'-diindolylmelhane induces apo ptosis in human cancer cells and that the induction of apoptosis is in dependent of p53 pathway. (C) 1996 Academic Press, Inc.