Abstract 3573: 17β-estradiol enhances hPygopus2 expression via ERα-SP1 promoter complexes

• Published in: Cancer research (Chicago, Ill.) Ill.), 2013-04, Vol.73 (8_Supplement), p.3573-3573
• Main Authors: Tzenov, Youlian R., Andrews, Phillip G., Kao, Kenneth R.
• Format: Article
• Language: English
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/1538-7445.AM2013-3573

Background: The chromatin remodeling protein Human Pygopus2 (hPYGO2) is widely overexpressed in, and required for the proliferation of several cancer cell lines derived from a variety of tumors. Because of the requirement of hPYGO2 for the G1/S cell cycle transition, its cell cycle dependent expression and its regulation by the Retinoblastoma protein in breast cancer (BC) cells, we hypothesized a fundamental link to the cell cycle. Thus, due to their predominant role in BC, we tested if 17β-estradiol (E2) would cause upregulation of hPYGO2 through Estrogen receptor alpha-SP1 transcription factor (ERα-SP1) promoter complexes.Methods: Eight ERα positive (ER+) and negative (ER-) BC cell lines were grown in low serum conditions and treated with ERα agonists and/or antagonists. mRNA levels were analyzed by Q-PCR and protein by immunoblot. ERα and SP1 promoter binding sites and DNA binding domains were functionally inactivated by site-directed mutagenesis. ERα and SP1 occupancy at the hPYGO2 promoter after treatment with various activators/inhibitors was analyzed by chromatin immunoprecipitation assays. Cell cycle progression was assessed by flow cytometry.Results: hPygopus2 mRNA and protein levels were higher in ER+ BC cells relative to ER- cells. ERα agonists induced, while antagonists inhibited, hPygopus2 mRNA and protein expression. ERα and SP1 occupancy at the hPYGO2 promoter required intact promoter binding sites and functional DNA binding domains. E2 increased, while Fulvestrant decreased, ERα binding to the hPYGO2 promoter while having no effect on SP1 binding. SP1 directed siRNA reduced SP1 occupancy at the hPYGO2 promoter and decreased hPygopus2 mRNA and protein expression in both ER+ and ER- cells. Treatment with betulinic acid, an SP1 inhibitor, resulted in cell cycle arrest in ER- BC cell lines.Conclusion: Our findings indicate that ERα and SP1 regulate hPygopus2 expression via promoter binding and that SP1 continues to play a role in hPYGO2 regulation in ER- cells, thereby revealing the potential efficacy of betulinic acid as a treatment for endocrine-disruptor resistant BC. Citation Format: Youlian R. Tzenov, Phillip G. Andrews, Kenneth R. Kao. 17β-estradiol enhances hPygopus2 expression via ERα-SP1 promoter complexes. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3573. doi:10.1158/1538-7445.AM2