The Single And Joint Effects Of BPA, DES And 4-CP On MCF-7 Cells

With the rapid development of agriculture, industry, economy and science, many chemicals were synthesized, entering the environment through various transport and transformation pathways. As a large class of these chemicals, xenoestrogens (XEs) exert their estrogenic effects by simulating or interfering with the ways that endogenous estrogens work. Almost existing in everywhere, XEs were detected not only in environment mediums such as soil, water, sediments, air and so on, but also in animal organisms as well as in human body. This indicated that humans were exposed to lots of XEs at all times. At the same time, a large number of researches showed associations between XEs exposure and development of endocrine-related diseases, including breast cancer, endometrial cancer, ovarian cancer, cervical cancer, prostate cancer, etc.In the present study, the three synthetic estrogens with similar structure, bisphenol A (BPA), diethylstilbestrol (DES) and 4-Cumylphenol (4-CP) were selected as target compounds. The ER (estrogen receptor) positive human breast cancer MCF-7 cells were chosen as the experimental cells. Cell viability assay was used as evaluation basis to examine the single estrogenic effects and the joint effects of BPA, DES,4-CP and physiologic concentrations of 17 β-estradiol (E2). In addition, western blot analysis was performed to explore the influence of the single XEs and the mix on the expression of estrogen receptor a (ERa), estrogen-related receptor y (ERRy) and anti-apoptosis protein Bcl-2. The main conclusions were as follows:(1) BPA, DES and 4-CP could increase the proliferation of MCF-7 cells in low dose and inhibit the proliferation in high dose, which act as low-dose and non-monotonic effect. In addition, they increased or inhibited the proliferation of MCF-7 cells via a time-dependent manner. Their potency to induce the proliferation of MCF-7 cells followed the rule of DES> BPA> 4-CP, and their toxicity in high dose followed the sequence of DES> 4-CP> BPA.(2) BPA, DES and 4-CP could affect the proliferation of MCF-7 cells by combining with ERa, activating the genomic pathway. Moreover, ERRy was also a important regulator in cell proliferation. And the binding affinity of these four XEs to ERa and ERRy in the order of E2> DES> 4-CP> BPA and BPA/4-CP> DES> E2, respectively. In the single XEs exposed assay, compared with the other two ERs, there was a more significant association between the expression of Bcl-2 and the corresponding cell proliferation rate, which indicated that XEs could affect cell proliferation by acting on apoptosis protein family.(3) The binary mixture of BPA and DES exerted stronger estrogenic activity compared with single BPA or DES. The possible reason was that BPA might improve the low binding affinity of DES to ERRy, meanwhile, DES enhanced the low binding affinity of BPA to ERa. However, the ternary mixture of BPA, DES and 4-CP showed an antagonism on cell proliferation, which indicated that the mix of BPA, DES and 4-CP weakened their estrogenic effects. But for the ternary mixtures, compared with the binary mixture, their effects on cell proliferation was reduced. And with the changes in concentrations of the three XEs, their influence on the expression of ERa, ERRy and Bcl-2 varied.(4) E2 with physiologic concentrations significantly improved the ability of single XEs to accelerate cell proliferation, for the reason that XEs might improve the low binding affinity of E2 to ERRy, and E2 enhanced the low binding affinity of XEs to ERa. Conversely, once combined E2 with the other two or three XEs, the estrogenic effects were inhibited, and many experiment groups almost lost its estrogenic activity. But the expression of ERa, ERRy and Bcl-2 was irregular, which meaned that the mix exerted estrogenic effects through more complex pathways.