CRABP2 and lung cancer: In order to explore whether the expression of CRABP2 is a potential tumor-related gene, we first analyzed the changes in the expression of CRABP2 in all tumors through the GEPIA database (http://gepia2.cancer-pku.cn/#general), and the results showed that the expression of CRABP2 in ovarian cancer, lung cancer, endometrial cancer, and breast cancer was significantly increased (Fig. 3A), which implies that CRABP2 is an essential oncogenic gene in cancer.