As an example, HER2 induces taxane resistance in breast cancers through signal amplification that: 1) induces drug efflux pumps including the ATP-binding cassette, sub-family B, member 1 (ABCB1) and ABCC3; 2) enhances the expression of drug metabolism proteins such as glutathione S-transferase P1 (GSTP1) and cytochrome P450 3A4 (CYP3A4); and 3) stimulates the expressions of cell survival proteins such as survivin, p21, and p53, etc3. The gene discussed is CYP3A4; the disease is breast cancer.