Bisphenol A and estrogen induce proliferation of human thyroid tumor cells via an estrogen-receptor-dependent pathway

Abstract

Objective: To determine the relationship between papillary thyroid carcinoma and environmental exposure to bisphenol A (BPA) or 17-β estrogen (E₂) by assessing the effects of these compounds on estrogen receptor expression and AKT/mTOR signaling.

Methods: The effects of low levels of BPA (1mM-10nM) and 17β-estradiol (E2, 0.1mM-1nM) on ER expression and cellular proliferation were determined in human thyroid papillary cancer BHP10-3 cells. Protein and mRNA levels of estrogen nuclear receptors (ERα/ERβ) and membrane receptors (GPR30) were determined by immunofluorescence assay, Western blotting, and RT-PCR, respectively, and proliferation was assessed by CCK-8 assay.

Results: The proliferative effects of BPA and E₂ were both concentration- and time-dependent. Expression of ERα/ERβ and GPR30 were enhanced by BPA and E_2. BPA and E₂ could quickly phosphorylate AKT/mTOR. Moreover, ICI suppressed ERα expression and activated GPR30 as did G-1. G-15 reversed the effects of E₂ on GPR30 and AKT/mTOR, but did not alter the effect of BPA.

Conclusions: BPA influences thyroid cancer proliferation by regulating expression of ERs and GPR30, a mechanism that differs from E₂. In addition, ICI and G-15 may have the potential to be used as anti-thyroid cancer agents.

Keywords: AKT; Bisphenol A; Estrogen receptor; Thyroid cancer; mTOR.