Lactic acid exposure alters lysophosphatidic acid receptor-mediated regulation of growth and motility in pancreatic cancer cells.

Lysophosphatidic acid (LPA) receptor signaling contributes to the regulation of cancer cell functions. Lactic acid serves not only as an important energy source for cancer cells but also activates various signaling pathways that influence cancer cell behavior. To investigate the roles of LPA receptors in the malignant behavior of pancreatic cancer PANC-1 cells, PANC-LA1 and PANC-LA5 cells were generated by culturing PANC-1 cells with 1 or 5 mM lactic acid, respectively, for approximately 3 months. LPAR1, LPAR3, and LPAR5 expression levels expression levels were elevated, whereas LPAR2 expression was reduced in PANC-LA1 and PANC-LA5 cells compared with PANC-1 cells. PANC-1 cell growth was inhibited by LPA. Conversely, PANC-LA1 cell growth remained unchanged in response to LPA, and LPA increased PANC-LA5 cell growth. The motility of PANC-LA1 and PAN-LA5 cells was markedly elevated compared with that of PANC-1 cells. LPA further enhanced PANC-LA1 and PAN-LA5 cell motility but did not affect PANC-1 cell motility. In the presence of LPA, AM966 inhibited, whereas TC LPA5 4 stimulated PANC-LA5 cell growth and PANC-LA1 cell motility. Although GRI-977,143 increased PANC-LA5 cell growth, it reduced PANC-LA1 cell motility. (2S)-OMPT increased PANC-LA5 cell growth and PANC-LA1 cell motility. When cells were cultured in serum-free media, the viability of PANC-LA1 and PANC-LA5 cells was higher compared with that of PANC-1 cells. PANC-LA5 cell growth and PANC-LA1 cell motility were inhibited by AZD3965 and galloflavin. These findings indicate that LPA receptor signaling is involved in the regulation of PANC-1 cell behavior induced by long-term lactic acid exposure, with LPA1 and LPA3 acting as major positive regulators of proliferation and motility following long-term lactic acid exposure, whereas LPA2 and LPA5 exert distinct regulatory effects.