Abstract P6-01-10: Estrogen receptor β2 and β5 increase expression of ABCG2 and drug resistance of the triple- negative breast cancer cell line SUM159

Abstract

Abstract Recent clinical studies indicate that estrogen receptor β2 (ERβ2) and β5 (ERβ5) expression in TNBC correlates to worse prognosis. We have expressed ERβ2 and ERβ5 in the triple negative cell line SUM159. Estrogen receptors β2 and β5 are highly similar to estrogen receptor β1, except for a truncated C-terminus making the remaining ligand -binding domain incapable of binding to estrogen. In addition, at the C-terminus, ER β2 and β5 have a unique peptide each of 27 and 4 amino acids in length respectively. Stably expressing ERβ2 and ERβ5 using a transposon integrated, tetracycline- regulated expression system increases expression of the drug resistance gene, ABCG2 in the triple negative SUM159 cells. Furthermore, we also find that the cells become more resistant to treatments with paclitaxel. We find that ERβ2 and ERβ5 interact with HIF-1α and HIF-2α and are recruited to HIF response elements (HRE's) in chromatin. In agreement with this, we find that ERβ2 and ERβ5 are recruited to the ABCG2 promoter, which contains HRE's and is known to be a target of HIF signaling. We propose that ERβ2 and ERβ5 play a role in chemo - resistance of TNBC and that targeting these factors may reduce chemo resistance thus preventing tumor-relapses and their associated mortalities. Citation Format: Faria M, Gustafsson J-A, Strom A. Estrogen receptor β2 and β5 increase expression of ABCG2 and drug resistance of the triple- negative breast cancer cell line SUM159 [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-01-10.