To evaluate the effect of miR-205 on the responsiveness to Trastuzumab, HER2+ BC cell line SKBr3 has been transfected with 100 nΜ miR-205 precursor or negative control (miR-205 and miR-neg) for 24 h, and treated with 1 ug/ml Trastuzumab for the following 48 h. This evidence concerns the gene ERBB2 and breast cancer.