Analysis of the immunosuppressive state in patients with malignant brain tumors

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Background : Malignant glioma cells secreted both thrombospondin-1 (TSP-1) and transforming growth factor-b (TGF-β) and the expression of both cytokines correlated with malignancy of gliomas. (Neuropathology 20 : 161, 2000) TSP-I has a potential to activate a latent form of TGF-β.Purpose : Experiments were performed to elucidate whether 1) TSP-1 secreted by malignant glioma cells participates in a latent TGF-β activaticn, and 2) a synthetic peptide which are found In TSP-1 moleoule and has a function of adhesion Can inhibit a motility of glioma cells. We established an ELISA for measurement of TSP-1 secretion by malignant glioma Cells.Results :1) Role of TSP-1 in latent TGF-β activation : Neutralizing anti-TSP-1 mouse monoclonal antibody or rabbit polyclonal antibody was added to culture medium of malignant glioma cells. The active form of TGF-β In the supernatants was measured by ELISA Addition of the antibodies resulted in a decrease of the active TGF-β in the supernatants in a dose-related manner. This Indicates that TSP-1 participates in the latent TGF-b activation. (Neurol Med Chir (Tokyo), in press)2) Inhibition of motility of glioma cells by a synthetic peptide : To examine the role of TSP-1 in motility of glioma cells, malignant glioma cells wae treated with a synthetic peptide which includes three adhesion sites in TSP-1 molecule. The motility of glioma cells was Inhibited by the peptide in a dose-related manner. The result agrees with the previous observation that transfection of antisense TSP-1 cDNA into glioma cells resulted in a decrease of motility of glioma cells. (Manuscript submitted)3) Measurement of TSP-1 in culture supernatants by ELISA : A sandwich ELISA using mouse anti-TSP-1 antibody and rabbit antibody was established Concentrations of TSP-1 in culture supernatants of 9 glioma cell lines were 43 - 2431 ng/1 x 10^6 cells/24 hours (643 ± 838 ; mean ± SD), while that of malignant melanoma (DFB) was 7.5 ng/1 x 10^6 cells/24 hours.