The Influence of Retinoic Acid and Thalidomide on the Radiosensitivity of U343 Glioblastoma Cells

Background/aim: 13-cis-retinoic acid (RA) and thalidomide have shown a synergistic anti-proliferative effect on U343 glioblastoma (GBM) cells. In the present study, we test if their combined treatment might enhance the radiosensitivity of these cells. Materials and Methods: The radiosensitivity of U343 GBM cells was determined by the colony formation assay. Fibroblast growth factor-2 (FGF2) gene expression was determined by a quantitative polymerase chain reaction (qPCR). Results: RA up-regulated FGF2 gene expression, which was abrogated by thalidomide. No radiosensitisation by RA was observed under standard culture conditions with 10% serum, but enhanced radiosensitivity was observed under 1% serum during irradiation. However, a synergistic effect with thalidomide was not observed. Conclusion: Growth factors in the culture medium may mask radiosensitization by RA while autocrine expression of FGF2 did not seem to be protective. Importantly, the anti- proliferative effect of RA in combination with thalidomide would not compromise the radiosensitivity of these GBM cells. Glioblastoma multiforme (GBM) is a common and aggressive primary brain tumor of glial origin (45). Despite the use of