LGR5 and gastric cancer: In gastric cancer, activation of PGD2/PTGDR2 signaling pathway inhibits the JAK/STAT3 signaling pathway and downregulates the expression of stemness-associated proteins, such as octamer-binding transcription factor 4 (OCT4), leucine-rich repeat-containing GPCR-5 (LGR5), Sal-like protein 4 (SALL4), and NANOG, which inhibits the self-renewal ability of gastric cancer cells [20].