PTGDR and gastric cancer: Recently, Song et al. have identified a regulatory network in gastric cancer whereby claudin-4 expression is reduced by miR-596 and miR-3620-3p, which are in turn bound by lncRNA-KRTAP5-AS1 and lncRNA-TUBB2A acting as ceRNAs, resulting in increased claudin-4 expression, suggesting that non-coding RNAs play important roles in the regulatory network of oncogenes and tumor suppressors in gastric cancer [19].