The expression of different CLDNs has been shown to have prognostic significance in different cancers, for example, claudin-1 has been linked with prognosis in colon cancer [4], claudin-18 has been linked with prognosis in gastric cancer (GC) [5], and claudin-10 has been linked with prognosis in hepatocellular carcinoma [6]. This evidence concerns the gene CLDN18 and cancer.