In this study, we suppressed miR-155 activity by miRCURY LNATM microRNA inhibitor  and observed that caspase-3 activity increased by 2 folds in 75nmol concentration of inhibitor but Ovcharenko and colleagues showed that miR-155 caused suppression of apoptosis in MDA-MB-453 breast cancer and human T cell leukemia Jurkat cells by blocking caspase-3 activity by identification of genes that differentially influence TRAIL-induced apoptosis through siRNA and miRNA library screening.Totally our results were in consistent with the findings of this group (62). This evidence concerns the gene CASP3 and breast cancer.