ERBB2 and gastric cancer: To further characterize the different GCX models, we analyzed them by immunohistochemistry for the expression of p53 (P53), known to be mutated in about 50% of gastric adenocarcinomas [22], CDX2, marker for intestinal gastric cancer subtype [23] and HER2 [25], overexpressed in 15–20% of GC, (Fig. 1B).