ER81-shRNA Inhibits Growth of Triple-negative Human Breast Cancer Cell Line MDA-MB-231 In Vivo and in Vitro

The lack of effective treatment targets for triple-negative breast cancers make them unfitted for endocrineor HER2 targeted therapy, and their prognosis is poor. Transcription factor ER81, a downstream gene of theHER2, is highly expressed in breast cancer lines, breast atypical hyperplasia and primary breast cancers includingtriple-negative examples. However, whether and how ER81 affects breast cancer carcinogenesis have remainedelusive. We here assessed influence on a triple-negative cell line. ER81-shRNA was employed to silence ER81expression in the MDA-MB-231 cell line, and MTT, colony-forming assays, and flow cytometry were used to detectcell proliferation, colony-forming capability, cell cycle distribution, and cell apoptosis in vitro. MDA-MB-231cells stably transfected with ER81-shRNA were inoculated into nude mice, and growth inhibition of the cellswas observed in vivo. We found that ER81 mRNA and protein expression in MDA-MB-231 cells was noticeablyreduced by ER81-shRNA, and that cell proliferation and clonality were decreased significantly. ER81-shRNAfurther increased cell apoptosis and the residence time in G0/G1 phase, while delaying tumor-formation andgrowth rate in nude mice. It is concluded that ER81 may play an important role in the progression of breastcancer and may be a potentially valuable target for therapy, especially for triple negative breast cancer.