Additionally, the association between the expression levels of each gene and the progression-free interval (PFI) of GC patients was analyzed, indicating that the expression levels of MET, TKTL1, CLDN9, and CHST4 did not affect the PFI of GC patients, while the expression level of MIOX did (Additional file 2: Figure S2F). Here, CLDN9 is linked to gastric cancer.