FOLH1 and gastric cancer: Targeting biomarkers can be tumor-specific antigens or overexpressed oncoproteins, such as prostate-specific membrane antigen (PSMA) for prostate cancer (68, 69), epidermal growth factor receptor (EGFR) for lung cancer cells (36, 70), and human epidermal growth factor receptor 2 (HER2) for gastric cancer or breast cancer cells (37, 71).