In this study, we endeavored to extensively characterize the potential of ERBB2 as a clinical biomarker through a myriad of in vitro and in vivo diverse gastric cancer (GC) models and human tumors, with an overall objective of replicating GC tumor heterogeneity and identifying pathways/networks that could contribute to trastuzumab resistance. This evidence concerns the gene ERBB2 and neoplasm.