Anti-proliferative and pro-apoptotic effects of 3,3'-diindolylmethane in human cervical cancer cells.

The antitumor effects of Indo-3-carbinol (I3C) have been proven in many human carcinoma cells. However, the roles of 3,3-diindolylmethane (DIM), an important polymer converted from I3C under pH 5.0-7.0, on the growth and proliferation of cervical cancer HeLa and SiHa cells still remain unrevealed. In the present study, we investigated the potential anti-proliferative and pro-apoptotic effects of DIM on HeLa and SiHa cells. Cell proliferation was detected by Cell Counting kit-8 and apoptosis was analyzed by flow cytometry. In addition, morphological changes accompanying cell apoptosis were observed using an inverted microscope after Hoechst 33258 staining. In addition, expression changes of proteins involved in the MAPK and PI3K pathways were determined by western blotting. DIM treatment inhibited the proliferation and induced apoptosis of HeLa and SiHa cells significantly in a time- and dose-dependent manner. Moreover, SiHa cells were more sensitive to DIM treatment than HeLa cells (P<0.05). In addition, the expression of ERK, p38 and p-p38, which are involved in the MAPK pathway, was downregulated by DIM treatment. Another protein involved in the MAPK pathway, JNK, was upregulated. Furthermore, DIM treatment significantly suppressed the expression of Akt, p-Akt, PI3K p110α, PI3K p110β, PI3K class III, GSK3-β, p-PDK1 and p-c-Raf which are involved in the PI3K pathway. These results demonstrate that DIM exerts antitumor effects on HeLa and SiHa cells through its anti-proliferative and pro-apoptotic roles, especially for SiHa cells. The molecular mechanism for these effects may be related to its regulatory effects on MAPK and PI3K pathway and apoptosis proteins. DIM may be a preventive and therapeutic agent against cervical cancer.