identification of miRNA differential expression patterns in a new model of acquired letrozole resistance

Since differential miRNA expression patterns associated with acquired AI resistance have been poorly investigated, the aim of this study was to delineate the deregulation of miRNA expression associated with aromatase inhibitor (AI) response failure in new cellular models of AI resistance. For this purpose, we generated and characterized novel cellular models of acquired resistance to letrozole (Res-Let cells) and to anastrozole (Res-Ana cells) and performed microarray experiments to identify miRNAs whose expression was either deregulated between control (MCF-7aro) and resistant cells (Res-Let or Res-Ana). With the aim to select relevant miRNAs, two independent cell culture replicates were performed for each experimental condition. MCF-7aro and Res-Let cells were grown in the presence of androstenedione (AD) combined or not with letrozole. Two independent cell culture replicates for each experimental condition were used to generate total RNA. Total RNA was extracted from cell culture using a Qiagen RNA extraction kit and RNA quality was assessed using the BioAnalyzer 2100? (Agilent Technologies). Complex probes were produced from these RNA, then hybridized to GeneChip® miRNA 3.0 array according to the manufacturer's recommendations (Affymetrix). Res-Ana cells were grown in the presence of androstenedione (AD). Two independent cell culture replicates for each experimental condition were used to generate total RNA. Total RNA was extracted from cell culture using a Qiagen RNA extraction kit and RNA quality was assessed using the BioAnalyzer 2100 (Agilent Technologies). Complex probes were produced from these RNA, then hybridized to GeneChip® miRNA 3.0 array according to the manufacturer's recommendations (Affymetrix).