The Research On The Proliferation Toxicity Of Three EDCs To Two Estrogen-dependent Cancer Cells

Any materials, in the traditional sense, will produce toxicity to the body as long as it reaches a certain quantity or concentration, but doesn’t have the corresponding toxicity when lower than the safe threshold. Toxicologists have believed that higher doses of chemicals will cause greater effects than low doses, that is "the dose makes the poison". Recently, a great deal of researches on endocrine disrupting chemicals (EDCs), have questioned the traditional eco-toxicology concept. XEs, as a typical kind of EDCs, are capable of eliciting biphasic dose responses for different endpoints at many organization levels, especially for the low-dose and non-monotonic interference effects. Therefore, the low-dose and non-monotonic effects cannot be inferred and predicted by high-dose exposure experiments, and the occurrence mechanisms are still unclear as well. Moreover, EDCs pervasively exist in the aquatic environment which is gaining attention from more and more researchers, so the integrated toxicities of EDCs and detailed mechanisms need to be further studied.Based on cell proliferation experiments, classical estrogen-dependent breast cancer MCF-7, MDA-MB-231 cells and hepatoma HepG2 cells were adopted as the study subject.1) Different concentrations of three typical EDCs including estrogens (i.e.,17-β-estradiol, E2 and 17-α-ethynylestradoil), antiestrogens (i.e., tamoxifen, TAM and Fulvestrant, ICI 182,780), and androgens (i.e., testosterone, TEST and androstenedione, AND) were used in the experiment, following treated with different stimulation time, the cell proliferation rates and drug susceptibility were tested in vitro by the 3-(4,5-dimethylthiazol-2)-2,5 diphenyltetrazolium bromide (MTT) assay.The results illustrated that there was an obvious exposure time-dependent cytotoxicity which was in the order of 12 h< 24 h< 48 h> 72 h; and the proliferation effects of all exposure EDCs on HepG2 cells were stronger than breast cancer cells. However, the proliferation toxicity did not show a two-way dose effect relationship curve when treated with estrogen, androgen or anti-estrogen. All exposure concentrations of various EDCs promoted cell proliferation except for TAM (10-5 mol/L) and TEST (10-5 mol/L).2) The cell proliferation maximum responses time-48 h was selected as the stimulated time for the joint-effect experiments. Simultaneously, E2 and TEST with the strongest and the weakest cell proliferation effects concentrations were use as the substrate for binary or ternary joint toxicity of EE2, antiestrogens (TAM and ICI 182, 780) and androgens (TEST and AND). The results showed that the joint exposure can produce synergistic or antagonistic effects for different tissues or cells even the different cancerous cells of the same tissue.3) In order to explore the cytotoxic mechanisms of different XEs, the relative expression levels of three kinds of estrogen receptor mRNA including ERα36, ERa66 and ERβ were detected by Real-time fluorescent quantitative polymerase chain reaction (RT-PCR). The results showed that the mRNA of three estrogen receptors were up-regulated or down-regulated with the inducements of all kinds of examined EDCs-whether with estrogens, with antiestrogens, or with androgens, indicating that cell proliferation effects were regulated by three kinds of ER mRNA. Particularly, the AND the TEST, as a kind of typical androgens, can stimulate the ER mRNA expression in different ways. In particular, the AND the TEST, as a kind of typical androgens, also can stimulate the ER mRNA expression in different ways.