Anja Pickhard, Johanna Margraf, Guido Piontek, Andreas Knopf, Rudolf Reiter, Anne-Laure Boulesteix and Jürgen Schlegel
Background: It is well documented that low dose ionizing radiation induces migration of glioma cells, but the mechanisms are still poorly understood. The aim of the current study was to elucidate the intracellular signal transduction pathways of radiation induced migration in human glioma cells.
Methods: Migration was assessed via a wound healing assay. In addition, tumor cell proliferation was evaluated with a MTT colorimeritric assay using 3 glioma cell lines (LN18, LN229, LNZ308). The cells were treated with increasing doses of irradiation (2Gy, 5Gy, 8Gy) in the presence or absence of EGF or inhibitors of the EGFR or downstream pathways (AG1478, LY294002, PD98059). Biochemical activation of EGFR, Akt/PKB and MAPK/ERK was examined by Western blot analysis.
Results: Irradiation induced a dose dependant intense increase of migrating cells and a decrease of proliferation. The inhibition of PI3K by LY294002 (50 µmol/L) reduced the radiation-induced migration (LN18: p<0.001, LN229: p=0.16, LNZ308: p=0.13), the blockade of MEK1 by PD98059 (50 µmol/L) was also effective (LN18: p=0.036, LN229: p=0.021, LNZ308: p=0.021). After irradiation, no effect on EGFR or the downstream pathways was observed in Western blot analysis.
Conclusion: Our results demonstrate that the downstream pathways of EGFR are involved in radiation induced migration of glioma cells.
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