Lysophosphatidic acid (LPA) is a simple physiological lipid and exhibits several biological functions by binding to G-protein-coupled LPA receptors (LPA receptor-1 (LPA1) to LPA6). The present study aimed to evaluate whether LPA signaling via LPA2 and LPA5 is involved in the chemoresistance to anticancer drugs in colon cancer DLD1 cells. In cell survival assay, cells were treated with fluorouracil (5-FU) every 24 h for 2 days. The cell survival rate to 5-FU of DLD1 cells was significantly decreased by LPA treatment. In the presence of LPA, the cell survival rate to 5-FU was significantly elevated by LPA5 knockdown. Before initiation of the cell survival assay, cells were pretreated with an LPA2 agonist, GRI-977143. The cell survival rate to 5-FU was markedly increased in DLD1 cells treated with GRI-977143. In the presence of GRI-977143, the elevated cell survival rate of DLD1 cells was reduced by LPA2 knockdown. To assess the effects of LPA2 and LPA5 on the enhancement of chemoresistance, long-term 5-FU treated (DLD-5FU) cells were generated from DLD1 cells. The cell survival rate to 5-FU of DLD-5FU cells were significantly elevated by LPA5 knockdown. GRI-977143 treatment increased the cell survival rate to 5-FU of DLD-5FU cells. These results suggest that LPA2 promotes and LPA5 suppresses the acquisition of chemoresistance in colon cancer cells treated with anticancer drugs.
Keywords: LPA5; anticancer drugs; chemoresistance; colon cancer cells; lysophosphatidic acid.