Differential effects of purinergic signalling in Gastric Cancer derived cells through P2Y and P2X receptors

Gastric Cancer (GC) is the one of the most prevalent cancer and one of the leading causes of cancer-induced deaths. Previously, we have found that the mRNA for the purinergic P2Y2 receptor is significantly increased in GC samples as compared to adjacent healthy mucosa taken from patients diagnosed with GC. In this work, we studied in detail the purinergic signaling in the gastric adenocarcinoma-derived AGS cell line and compared to the non-tumoral epithelial cell line, GES-1. In AGS cells, we detected the expression of several purinergic receptors, and we found important differences in the expression pattern compared to GES-1 cells. Functional studies revealed a strong contribution of P2Y2 receptors in the increase in intracellular calcium, elicited by ATP, UTP and the specific agonist MRS2768. Purinergic responses were preserved in the absence of extracellular calcium and inhibited by the P2Y2 antagonists suramin and AR-C118925. In contrast, in GES-1 ATP induced significantly higher responses as compared to UTP and P2X receptor antagonists were able to partially block these responses. Proliferation studies showed that ATP regulates AGS cell proliferation in a biphasic manner, slightly increasing cell proliferation at 10 and 100 uM, but inhibiting at 300 uM ATP. On the other hand, 1-300 uM UTP, a selective P2Y2 agonist, increased concentration-dependently cell proliferation. The effects of UTP and were prevented by wide range and specific purinergic antagonists. In contrast in GES-1 cells ATP only decreased cell-proliferation in a concentration dependent manner and UTP had no effect. Notably, the application of purinergic antagonist alone was enough to change the rates of AGS cells proliferation, indicating that nucleotides released by the cells can signal through paracrine and autocrine mechanisms. Finally, in tumor-derived biopsies, we found that whereas the expression of P2Y2 is significantly increased, the expression of P2X4 is significantly decreased, as compared to healthy tissues. Taken together, these results demonstrate the involvement of different purinergic receptors and signaling in GC, and the pattern of expression changes in tumoral cells, and this change probably directs ATP and nucleotide signaling from an anti-proliferative effect in healthy cells to a proliferative effect in tumoral cells.