THE EFFECT OF TRANSFORMING GROWTH FACTOR-BETA(2)-SPECIFIC PHOSPHOROTHIOATE-ANTI-SENSE OLIGODEOXYNUCLEOTIDES IN REVERSING CELLULAR IMMUNOSUPPRESSION IN MALIGNANT GLIOMA

This in vitro study was aimed at restitution of transforming growth factor (TGF)-beta2-mediated suppression of T-lymphocyte activation within malignant gliomas. In early-passage tumor cell cultures of two glioblastomas (HTZ-153 and HTZ-209) and one malignant astrocytoma classified as World Health Organization Grade III (HTZ-243), autologous peripheral blood mononuclear cells were activated by interleukin-1alpha and interleukin-2 in vitro (lymphokine-actived killer cells) and tested for cytotoxic and proliferative activity. In expression studies (Western blot and Northern hybridization) of all three tumors, TGF-beta could be detected at the protein and messenger ribonucleic acid (mRNA) levels. A polyclonal anti-TGF-beta neutralizing antibody did not enhance lymphocyte proliferation upon stimulation with tumor targets (H-3-thymidine incorporation) and slightly stimulated lymphocyte cytotoxicity against autologous target cells. Preincubation of target cells for 12 hours with TGF-beta2-specific phosphorothioate-anti-sense oligodeoxynucleotides (S-ODN's) did. however, enhance lymphocyte proliferation up to 2.5-fold and autologous tumor cytotoxicity up to 60%, compared to controls not treated with S-ODN's. Incubation of tumor cells with TGF-beta2-specific S-ODN's resulted in decreased TGF-beta-specific immunoreactivity in cultured glioma cells, in reduced TGF-beta2 protein concentration (Western blot), and in a change in the expression pattern of TGF-beta2 mRNA's. These observations may have implications for in vivo and in vitro activation of a cellular immune response against autologous malignant glioma cells.