Objectives: Excess estrogen states, such as those generated by obesity, have long been associated with the development of type I endometrial cancers. Epidemiological studies have linked consumption of isoflavones with a decreased incidence of endometrial malignancy. Thus, our goal was to assess the effect of the isoflavones, novasoy and genistein, on cell proliferation, cell cycle, apoptosis, progesterone receptor (PR) and estrogen receptor-alpha (ERα) expression and the AKT/mTOR and MAPK pathways in endometrial cancer cells.
Methods: The endometrial cancer cell lines ECC-1 and RL-95-2 were used. Cell proliferation was assessed with MTT assay after exposure to novasoy and genistein at varying concentrations. Cell cycle progression was analyzed by flow cytometry. Apoptosis was assessed by flow cytometery for annexin V expression and ELISA for caspase-3 activity. Expression of ERα, PR and hTERT mRNA were evaluated using real time RT-PCR. Western immunoblotting was performed to evaluate the effects of novasoy and genistein on the AKT/mTOR and MAPK signaling pathways.
Results: Novasoy and genistein inhibited cell growth in a dose-dependent manner in both cell lines through induction of cell cycle G2 arrest and apoptosis. Treatment with novasoy and genistein decreased hTERT expression in a dose-dependent manner. Genistein decreased ERα mRNA expression while increasing PR expression. Genistein induced phosphorylation of p42/44 in a dose dependent manner in both cell lines but reduced phosphorylation of S6 in only the RL-95-2 cells.
Conclusions: Novasoy and genistein inhibited cell proliferation through varying pathways in different cell lines but included decreased ERα expression and subsequent alteration in the expression of proteins upstream and downstream of the AKT/mTOR and MAPK pathways. Thus, isoflavones may be a promising therapeutic agent in the treatment and prevention of endometrial cancer.
Keywords: Endometrial cancer; MAPK pathway; estrogen receptor; genistein; mTOR pathway; novasoy.