These results suggested that HLX22 in combination with HLX02 preferentially promoted apoptotic cell death in gastric cancer cells with 3 + HER2 expression compared to breast cancer cells with 3 + HER2 expression, implying that there were intrinsic differences in the tumor biology between HER2-positive gastric cancer and HER2-positive breast cancer in response to dual HER2 blockade. This evidence concerns the gene ERBB2 and breast carcinoma.