MicroRNA expression profiling of tamoxifen sensitive and resistant ER+ breast cancer cell lines

Tamoxifen is an effective anti-estrogen treatment for patients with estrogen receptor-positive (ER+) breast cancer. However, about 30% of such patients receiving tamoxifen as an adjuvant therapy experience recurrence within 15 years, and most patients with advanced disease eventually develop resistance to tamoxifen. To elucidate the underlying molecular mechanisms of tamoxifen resistance, we performed a systematic analysis of miRNA-mediated gene regulation in three clinically-relevant tamoxifen-resistant human breast cancer cell lines (TamRs) compared to their parental tamoxifen-sensitive MCF-7/S0.5 cell line. Alterations in the expression of 131 miRNAs in tamoxifen-resistant vs. parental cell lines were identified, 22 of which were common to all TamRs using both sequencing and LNA-based quantitative PCR technologies. ER+ and tamoxifen sensitive breast cancer cell line (MCF-7/S0.5) and its derived tamoxifen resistant clones: TAMR-1, TAMR-4 and TAMR-8 were miRNA expression profiled in triplicates of each using Exiqon's miRCURY LNA based microRNA Ready-to-use PCR, Human panel I+II, V2.R (Exiqon, product number 203608).