PTGDR2 and gastric cancer: Yes-associated protein (YAP) is involved in the progression of many malignancies and is thought to enhance the expression of GCSCs surface markers and self-renewal GCSCs via TGF-β-activated kinase 1 (44) or by inhibiting the expression of lipocalin-type prostaglandin D2 synthase (L-PTGDS) and prostaglandin D2 receptor 2 (PTGDR2) (45).And the increased expression of GCSCs markers and renewal of GCSCs will in turn promote the progression of GC and the self-renewal of GC cells (45).