Combinational Anti-Cancer Effects of Natural Phytochemicals in Human Endometrial Cancer Cells

Endometrial cancer is the most common gynecological cancer in the United States. Ishikawa endometrial cancer cells, a human estrogen responsive and well-differentiated adenocarcinoma cell line, is being used as a model system to characterize anti-cancer responses of individual and effective combinations of natural plant-derived compounds.  Treatment of Ishikawa cells with either 3,3’-diindolylmethane (DIM) or artmesinin (ART) for 48 hours dose dependently induced a G1 cell cycle arrest and apoptotic response that was observable at 30 µM DIM and 300 µM ART.  Flow cytometry revealed that cells treated with DIM (15 µM ) and ART (150 µM) for 48 hours show only minor increases in the percentage of cells arrested in G1.  In contrast, treatment with a 15 µM DIM and 150 µM ART combination showed a striking synergistic anti-proliferative response with a 10-fold percent increase in the number of G1 phase arrested cells compared to cells treated with each phytochemical alone.  Protein analysis by western blots revealed that the combined treatment with suboptimal concentrations of DIM and ART induced significant decreases in expression of the CDK2 and CDK4 G1-acting cell cycle genes. Treatment with a combination of DIM and ART selectively strongly down-regulated the protein and transcripts expression of the HER2 member of the EGF receptor gene family, an important growth factor signaling pathway in endometrial cancer cells.  Future work is directed at understanding the cellular mechanism and in vivo tumor consequences by which combinations of DIM and ART synergistically act to mediate their anti-cancer signaling in human endometrial cancer cells.