Impact of low concentrations of phthalates on the effects of 17β-estradiol in MCF-7 breast cancer cells

Objective: To explore whether lower concentrations of phthalates interfere with the effects of 17β-estradiol on the growth of MCF-7 breast cancer cells.

Materials and methods: MCF-7 cells were treated with 17β-estradiol (E₂), phthalates, including butyl benzyl phthalate (BBP), di(n-butyl) phthalate (DBP), and di(20ethylhexyl) phthalate (DEHP), or with both E₂ and phthalates, all at 10nM. After incubation for 48 hours, the cells were harvested and extracted for MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. The proteins involving proliferative and apoptotic pathway were then evaluated using Western blot analysis.

Results: In MCF-7 cell cultures, the MTT assay revealed a significant increase in cell viability with E₂ and these three phthalates, and significantly more cell proliferation with the combination of E₂ and phthalates. Proliferating cell nuclear antigen, as well as phosphatidylinositide 3-kinase (PI3K) and p-Akt, were all substantially increased in cultures with E₂, phthalates, and the two combined. An additive effect of phthalates on the obvious increase of Bcl-2 and ER α expression was also noted in the presence of E₂.

Conclusion: The present study demonstrates that even at a very low concentration, BBP, DBP, and DEHP were not only still capable of displaying estrogenic activity, but also of inducing an additive proliferative effect through the PI3K/Akt signaling pathway and preventing apoptosis in the presence of E₂. Therefore, the effects of current reference doses for phthalates defined by the government, especially for premenopausal women, should be further considered.