Irradiation of healthy brain alters expression of genes involved in cell motility and invasiveness of glioblastoma

Traumatic brain injury is known to cause proliferation and migration of astrocytic and neuronal cells. To find out whether irradiation may influence migration of intracranial tumors, we performed expression profiling of orthotopically implanted glioblastomas following irradiation to the contralateral (non-diseased) hemisphere. Microarrays were used to identify differentially expressed genes associated with glioblastoma-malignancy in distinct tumor compartments following irradiation of brain tissue of contralateral (non-diseased) hemisphere. Differentially expressed genes were the object to functional network analysis with Ingenuity pathway analysis software We orthotopically implanted 2.5x10^6 cells of the human glioblastoma cell line U87 MG into immunodeficient NSG mice. Following tumor detection in serial imaging, fractionated irradiation with 3 x 5 Gy was applied to the contralateral hemisphere. Non-irradiated tumor-bearing mice served as control group. Following snap-freezing of brains, tumor cores and peripheries were separated using laser-capture microdissection (LCM) and subjected to RNA isolation and Affymetrix microarray hybridisation. We sought to separately compare gene expression profiles following contralateral irradiation within the two tumor compartments.