ERBB2 and breast cancer: Moreover, in the serum of HER2-positive patients who did not respond to HER2-targeted drug treatment with trastuzumab with or without lapatinib, TGFβ1 levels were significantly higher in exosomes than in patients who had a complete response (CR) or partial response (PR), indicating a possible new mechanism-of-action for NmU in HER2-positive BC that increases resistance to the anti-tumor immune response.