LPAR2 receptor stimulates progression of gastric cancer through β‐catenin signaling pathway

Lysophosphatidic acid (LPA) is a simple lipid that has been implicated in cellular homeostasis and pathology of different cancer by binding with G-protein coupled receptors (LPAR1-6). The aberrant Wnt signaling pathway has been reported to facilitate a crucial role in tumorigenesis and therapy responses. Although dysregulated β-catenin signaling pathway has been established as a critical mediator of gastric cancer, whether LPA and LPAR2 play a role in the β -catenin signaling pathway during gastric cancer progression remains elusive.Our present study explored an unknown role of LPA and LPAR2 in LPA-induced activation of β-catenin and its downstream signaling mechanism in β-catenin mediated gastric cancer.We analyzed the mRNA levels of different LPA receptors in human gastric cancer by ULCAN database using TCGA dataset. LPA ELISA, Western blotting, and immunohistochemical analysis were done in the human normal stomach and cancerous stomach to measure the LPA level and check the expression of different LPA receptors. To investigate the functional role of LPAR2 in LPA-mediated gastric cancer progression, we performed ECIS proliferation, migration assay, scratch assay, and transwell invasion assay in LPA or LPA with LPAR2 antagonist treated cells. To elucidate the molecular mechanism of LPA-mediated gastric cancer progression, we performed Western blotting, Real-time PCR, Luciferase assay, Immunocytochemistry, and nuclear fractionation in gastric cancer cells treated with LPA or LPA with LPAR2 antagonist.We confirmed a robust increase in LPA level and significantly increased expression of LPAR2 receptor in human gastric cancer tissue samples (P<0.001) by LPA ELISA, western blotting analysis, and immunohistochemistry, suggesting a possible role of LPA in gastric cancer through LPAR2 receptor. In cultured AGS and NCI-N87 gastric cancer cell line, LPA treatment increased proliferation, migration, and invasion activity, whereas LPAR2 receptor antagonist abrogated the LPA induced effect. Further, when the cells were treated with LPA, it increased the β-catenin activity, nuclear localization of β -catenin, and the expression of the downstream target genes of the β-catenin signaling pathway. In addition, we confirmed LPA-induced activation of the β-catenin signaling pathway through the LPAR2 receptor by using LPAR2 antagonist and by knockdown of LPAR2 where LPAR2 antagonist treatment or LPAR2 knockdown rescued LPA induced activation of the β -catenin signaling pathway in both cell lines.we established a novel LPA-LPAR2-β-catenin signaling pathway in the progression of gastric cancer. All our results support that LPAR2 is a potential marker and target for developing novel therapeutic strategies in the treatment of gastric cancer.