ERBB2 and breast cancer: Given the lack of clinical evidence of association between HER2-Δ16 and resistance to trastuzumab in BC, as well as the lack of preclinical data on the anti-tumor efficacy of trastuzumab in xenografts carrying HER2-Δ16 [26], our data suggest that HER2-Δ16 was not a resistance mechanism to trastuzumab in GC when tested in the PDGCX model.