17Beta-estradiol Mediated Expression Of Hsp27 In Papillary Thyroid Cancer And Its Molecular Mechanism

Objective: To investigate the effect of 17β-estradiol on the expression of Hsp27 in papillary thyroid cancer cells and its molecular mechanism.Methods: K1 and BCPAP cells were treated with 10-8 mol/L17β-estradiol(E2) for different time periods, the expression levels of Hsp27 mRNA in cells were detected by Real-time PCR, and the expression levels of Hsp27 protein in cells were detected by Western blot. K1 and BCPAP cells were treated with E2, PPT and DPN respectively, then detected the expression levels of Hsp27 by Western blot. RNA interference against ERα or ERβ(ERα siRNA or ERβ siRNA) was designed and synthesized, then transfected to K1 and BCPAP cells. The expression levels of Hsp27, ERα and ERβ in cells were analyzed by Western blot. The activity of Hsp27 promoter was evaluated by chromatin immunoprecipitation analysis(ChIP). The cell viability was evaluated by MTT assay. The caspase-3 activity was determined by enzyme labeled analytical instrument. The interaction between Hsp27 and Procaspase-3was detected by co-immunoprecipitation assay.Results: K1 and BCPAP cells were treated with 10-8 mol/L E2 for different time periods, the expression levels of Hsp27 mRNA and protein in K1 and BCPAP cells were increased gradually with the increasing hours for E2 treatment, and peaked at 24 h(P<0.05). PPT could promote the expression levels of Hsp27 protein(P<0.05), while DPN could reduce the expression levels of Hsp27 protein(P<0.05). Pretreatment with ERα siRNA obliterated the inductive effects of E2 on Hsp27 protein expression levels(P<0.05), but pretreatment with ERβ siRNA increased the inductive effects of E2 on Hsp27 protein expression levels in K1 and BCPAP cells(P<0.05).ChIP result has confirmed that ERα protein could bind to the region of Hsp27 gene promoter in K1 and BCPAP cells. MTT and caspase-3 activity results suggested that the up-regulation of Hsp27 by ERα facilitates proliferation and confers resistance to apoptosis provoked by TNF-α(P<0.05). Meanwhile pretreatment with ERα siRNA and Hsp27 siRNA obliterated the inductive effects of E2 on the interaction between Hsp27 and Procaspase-3.Conclusion: 17β-estradiol can induced the expression of Hsp27 in K1 and BCPAP cells by an ERα-dependent manner, and Hsp27 is resistant to apoptosis.