Increased Cell Growth Response to Lysophosphatidic Acid (LPA) of Lung Cancer Cells via LPA Receptor Signaling Induced by Cooperative Action of Lymphatic Endothelial Cells and Fibroblasts.

Lysophosphatidic acid (LPA) receptors (LPA1 to LPA6) are implicated in cancer pathogenesis. Stromal cells within the tumor microenvironment contribute to the malignant progression of cancer cells. Given that stromal cells can contribute to the malignant behavior of tumor cells, this study investigated the role of LPA receptor-mediated signaling in modulating stromal cell-induced cancer cell growth. Lung cancer A549 cells were co-cultured with lymphatic endothelial SVEC4-10 cells and/or fibroblast 3T3 cells, or cultured in their respective supernatant. Co-culture with SVEC4-10 and/or 3T3 cells altered the expression of LPAR1, LPAR2, and LPAR5 genes in A549 cells. LPA enhanced A549 cell growth in the supernatant derived from co-cultured SVEC4-10 and 3T3 cells, exceeding the effects observed in the supernatant from SVEC4-10 or 3T3 cells alone. A549 cell growth was suppressed by AM966 (LPA1 antagonist) and TC LPA5 4 (LPA5 antagonist), and promoted by GRI-977143 (LPA2 agonist). Autotaxin (ATX) expression was upregulated in A549 cells co-cultured with SVEC4-10 and/or 3T3 cells, and lysophosphatidylcholine (LPC) treatment enhanced A549 cell growth in the co-culture supernatant of both cell types. Mouse lung cancer LL/2 cells also showed increased growth in response to LPA when cultured with the co-culture supernatant, and this effect was inhibited by AM966 and TC LPA5 4, and promoted by GRI-977143. These findings suggest that co-culture of SVEC4-10 and 3T3 cells more effectively promotes lung cancer cell growth through LPA receptor signaling than either cell type alone.