Claudin 1 (CLDN1) has beenfound to be highly expressed in GC and is a poor predictive disease marker bymediating tumor necrosis factor-α induced cell migration, enhancement ofproliferation, and metastasis while SULF1 has been found to besignificantly hypomethylated causing significant downregulated protein expression.25, , -28 This SULF1 downregulation may be indicative of aposttranslational modification, feedback loop, or degradation event viaprotein–protein interactions but is still unclear. This evidence concerns the gene CLDN1 and gastric cancer.