MDK and neoplasm: As expected, the trastuzumab treatment resulted in significant tumor growth inhibition in the xenografts expressing the MDK-HER2 fusion (TGI = 67%) (Figures 7B), but it showed no efficacy in the xenografts expressing the ZNF207-HER2 fusion (TGI = 2%) (Figures 7C), thus supporting the resistant mechanism to trastuzumab in GC.