One of estrogens in the body, 17β-oestradiol (E2), is a pleiotropic hormone that regulates the growth and differentiation of many tissues and also acts as a mitogen that promotes the development and proliferation of hormone-responsive cancers such as breast and ovarian carcinomas. Xenoestrogens are chemical compounds that imitate oestrogen in living organisms and are classified as a type of endocrine-disrupting chemical (EDC). Bisphenol A (BPA) is a widely used industrial compound, and also known as an EDC and especially a xenoestrogen. In this study, we examined the effect of E2 or BPA on the cell growth of BG-1 ovarian cancer cells in vivo and in vitro. In the cell proliferation assay in vitro, E2 or BPA increased the growth of the BG-1 ovarian cancer cells expressing oestrogen receptors (ER). Their proliferation activity was reversed by the treatment of ICI 182 780, a well-known antagonist of ER, which demonstrates that the cell proliferation by E2 or BPA is mediated by ER and BPA certainly acts as a xenoestrogen in the BG-1 ovarian cancer cells. Clearly, E2 and BPA increased the expression of cyclin D1, a factor responsible for the G1/S cell cycle transition. These reagents also decreased the expression of p21, a potent cyclin-dependent kinase (CDK) inhibitor that arrests the cell cycle in the G1 phase. As a result, they promoted the proliferation of BG-1 cells via upregulation of the cell cycle progression. In mice xenograft models transplanted with BG-1 ovarian cancer cells, E2 or BPA administration significantly induced the tumour proliferation compared with vehicle (corn oil) treatment for 10 weeks, which was identified by the measurement of tumour volume and histological analysis on tumour tissues such as hematoxylin and eosin (H&E) staining and BrdU incorporation assay. Taken together, as an EDC having a xenoestrogenic activity, BPA was demonstrated to have a risk of tumour proliferation in oestrogen-dependent cancers such as ovarian cancer.
This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Ministry of Education, Science and Technology (MEST) of government of Korea (no. 2011-0015385).
Treatment with bisphenol A and methoxychlor results in the growth of human breast cancer cells and alteration of the expression of cell cycle-related genes, cyclin D1 and p21, via an estrogen receptor-dependent signaling pathway