Objective: Glioblastoma cells produce cytokines with proinflammatory or immunosuppressive properties, or both, which, in addition to altered p53 gene expression, have been shown to be associated with glioblastoma resistance to radiotherapy. The reported data concerning cytokines have been isolated and sometimes discordant, and a comprehensive profile analysis of cytokines and their corresponding receptors in irradiated glioblastomas has received limited attention. The object of this study was to test the hypothesis that radiation alone in clinically relevant doses would not significantly alter expression of endogenous cytokines and their receptors in human glioblastoma celll ines with wild-type and mutant p53.
Design and method: Culture specimens of 4 glioblastoma cell lines of different p53 gene expression (U87, U118, U251, U373) were irradiated with cobalt 60 at a dose of 10 Gy. After 48 hours, radiosensitivity was defined through a colony formation assay, cell cycle distribution was analyzed by flow cytometry, and cytokine and cytokine receptor messenger-RNA (mRNA) profiles were defined with an RNase protection assay. Different single doses of radiation at varying time intervals after culture were applied also to wild-type p53 cell lines.
Results: All cell lines were relatively radioresistant at lower doses of 1 and 2 Gy. Immunosuppressive cytokine and cytokine receptor mRNA of the Th2 (IL-13Ralpha, IL-4) and Th3 family (TGF-beta1, 2 and 3, TGF-betaRI and RII) were expressed. In contrast, only 2 proinflammatory Th1 cytokine receptor genes (IFN-gammaRa and IFN-gammaRbeta), but no significant Th1 cytokine gene expression, were detected. Even though the population examined included a large fraction of reproductively dead cells, cytokine and cytokine receptor mRNA profiles were not altered significantly by irradiation in all cell lines, regardless of the p53 status.
Conclusion: These results suggest that cobalt irradiation alone at clinically relevant doses does not significantly alter the cytokine and cytokine receptor profiles in human glioblastoma cell lines.