ERK, PKC and PI3K/Akt Pathways Mediate Extracellular ATP and Adenosine-Induced Proliferation of U138-MG Human Glioma Cell Line

Abstract

Objective: Extracellular nucleotides and nucleosides induce proliferation in a set of human glioma cell lines. In this study we investigate the signal transduction pathways involved in ATP and adenosine-mediated proliferation in U138-MG human glioma cells. Methods: Cell proliferation was accessed through [³H]thymidine incorporation, cell counting and flow cytometry. Protein phosphorylation was detected through Western blotting. Results: ATP or adenosine (100 µ M) induced extracellular signal-regulated protein kinase (ERK), Akt and GSK3β phosphorylation. The increase in [³H]thymidine incorporation induced by ATP or adenosine was decreased when cells were incubated with LY 294002 (by ±90%), GF 109203X (by ±76%) or PD 098059 (by ±63%). The increase in cell numbers with ATP or adenosine was less after a 48-hour treatment of cells with ATP or adenosine plus GF 109203X (by ±66%) or LY 294002 (by ±83%). Percentage of cells in S phase was decreased in cells treated with LY 294002 plus ATP when compared to ATP- treated cells. Conclusion: Stimulation of purinergic receptors in U138-MG cells leads to cell proliferation mediated by PI3K/Akt, ERK and PKC signaling. It may be clinically important for pharmacological intervention in gliomas to associate purinergic receptor antagonists and signal transduction pathways blockers.