Temozolomide has anti-tumor effects through the phosphorylation of cPLA on glioblastoma cells.

Temozolomide is an alkylating agent used as the first line of treatment for glioblastoma. However, chemoresistance to temozolomide is common in glioma patients. In addition, there are likely many unknown mechanisms for the anti-tumor effects of temozolomide. It is known that an alkylating agent, sulfur mustard, activates cytosolic phospholipase A (cPLA₂) releasing arachidonic acid to suppress tumors. The present study was performed to elucidate the involvement of cPLA in the anti-tumor mechanisms of temozolomide. In three glioblastoma cell lines (GL261, U251MG and T98G), we performed several evaluations including cell viability, cell migration and apoptosis, to study temozolomide-induced anti-tumor effects. Further, we evaluated tumor size in the murine orthotropic glioblastoma model after oral administration of temozolomide. Finally, we investigated the phosphorylation of cPLA in GL261 cells treated with temozolomide, and clarified whether phosphorylation of cPLA affects cell growth. Temozolomide suppressed cell growth and cell migration in glioblastoma cells in vitro and showed anti-tumor effect in the murine orthotopic glioblastoma model in vivo. Furthermore, temozolomide increased phosphorylation of cPLA which was associated with suppression of cell growth. However, in MGMT high-expressing glioblastoma T98G cells, temozolomide could not suppress cell growth or cause phosphorylation of cPLA These findings indicate that temozolomide suppressed cell growth partly by phosphorylation of cPLA in glioblastoma cells. In addition, because temozolomide did not cause phosphorylation of cPLA in MGMT high-expressing glioblastoma T98G cells, phosphorylation of cPLA may be caused by DNA alkylation of temozolomide.