We analyzed RNA from 2 breast cancer cell lines (MDA-MB-231 (MM231) and MCF7) and exosomes derived from them We used Affymetrix miRNA-3 array to determine the miRNA profile to find out whether miRs content in exosomes and expression levels were different after 17β-estradiol . Overall design: Here, we performed a global profiling of differentially expressed miRNAs in breast cancer cell lines