A human glioblastoma multiforme cell line (U87) and its derived-spheroids were irradiated either using a conventional irradiation (CIR) or a CK-like irradiation (IIR) in which the 8 Gy was delivered intermittently over a period of 40 min. The ability of glioma cells to migrate into a matrigel matrix was evaluated on days 1-8 from irradiation. Irradiation with CK-driven IIR significantly increased the invasion potential of U87 cells in a matrigel-based assay. In contrast to CIR, IIR was associated with increased levels of TGF beta at four days (real-time PCR), beta 1-integrin at 4-5 d (real-time PCR and protein gel blot) and no elevation in phosphorylated AKT at days 4 and 5 (protein gel blot). Our data suggests that glioma cell invasion as well as elevations of TGF beta and beta 1-integrin are associated with IIR and not CIR.