Overexpressed miR-21 contributes to the resistance of HCC cells to interferon-α/5-fluorouracil [25], the acquired resistance of EGFR-TKI [23] and gefitinib resistance [24] in non-small cell lung cancer cells [23], and the acquired resistance to trastuzumab in breast cancer [20]. The gene discussed is EGFR; the disease is breast carcinoma.