CD147-knockdown or CD147-knockdown-plus-trastuzumab treatment reduced MAPK and Akt phosphorylation in all four cell lines compared with the controls, indicating that CD147 knockdown might increase the effects of trastuzumab on the MAPK and Akt pathways in HER2-positive breast cancer cells, and the effects of CD147 knockdown and trastuzumab were overlapping. This evidence concerns the gene ERBB2 and breast cancer.