Chk2-mediated G2/M cell cycle arrest maintains radiation resistance in malignant meningioma cells.

In continuation to our studies on radioresistance in meningioma, here we show that radiation treatment (7Gy) induces G2/M cell cycle arrest in meningioma cells. Phosphorylation of Chk2, Cdc25c and Cdc2 were found to be key events since interference with Chk2 activation and cyclin B1/Cdc2 interaction led to permanent arrest followed by apoptosis. Irradiated cells showed recovery and formed aggressive intracranial tumors with rapid spread and morbidity. Nevertheless, knock down of uPAR with or without radiation induced permanent arrest in G2/M phase and subsequent apoptosis in vitro and in vivo. In conclusion, our data suggest that combination treatment with radiation and uPAR knock down or other inhibitors resulting in non-reversible G2/M arrest may be beneficial in the management of meningiomas.