CLDN9 and gastric cancer: PAM, CLDN9, CHST6, SLC16A3, KDELR3, and CASP6 are regarded as biomarkers or prognosis genes in the signature, with reports revealing their expression in the areas of the prostate (Jimenez et al., 2001), endometrial lung adenocarcinoma (Wang Z.H. et al., 2019), Uveal Melanoma (Li et al., 2018), and gastric cancer (Wang Z. et al., 2019).