-4D3 treatment downregulates claudin-4, EGFR, and VEGF in cancer cells and inhibits cell proliferation-4D3 decreases gastric cancer stemness markers-Combined 4D3 and cis-diamminedichloroplatinum (CDDP) have a synergic anti-cancer effect-4D3 increases CDDP intracellular concentration-4D3 monotherapy inhibited the growth of well-differentiated gastric cancer in vivo but not poorly differentiated one-Concurrent CDDP and 4D3 exhibit higher anti-cancer activity compared to monotherapy in both tumors and improve mice survival. The gene discussed is EGFR; the disease is gastric cancer.