ERBB2 and breast cancer: Subsequent single-cell RNA sequencing investigations of HER2+ with the monoclonal antibody, Trastuzumab (Herceptin), successful in targeting HER2+ breast cancer cells (Wang et al. 2019b), re-affirmed previously highlighted gene sequences such as CLU and SEPP1 genes in trastuzumab-treated patients and indicated new gene signatures of interest such as the chemokine ligands CXCL1 and CXCL8 that were significantly downregulated under trastuzumab treatment (Wang et al. 2019a).