Effects of recombinant human tumor necrosis factor-α on the surface phenotype and the growth of human malignant glioma cell lines

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Abstract
Human malignant glioma cell lines and clones were incubated with various concentrations of recombinant human TNF-α, either alone or in combination with recombinant human IFN-γ. The surface expression of HLA-ABC (class I) antigens and β2-microglobulin, was significantly enhanced by TNF-α alone on every cell line and clone tested. After incubation with both TNF-α and IFN-γ, the surface expression of HLA-ABC antigens was only slightly higher than that observed with each cytokine alone. In contrast to IFN-γ, TNF-α had no effect on the surface expression of HLA-DR (class II) antigens. Moreover, the surface expression of HLA-DR induced by IFN-γ was unaffected by TNF-α. The increased expression of HLA-ABC antigens after treatment with TNF-α or IFN-γ correlated with increased levels of HLA-ABC-specific mRNA. In addition, TNF-α, like IFN-γ, selectively enhanced the surface expression of a tumor-associated antigen, Me14-D12, while it had no effect on the expression of various other surface antigens. In the absence of actinomycin D, TNF-α exhibited no direct cytotoxic/cytostatic effect on the glioma cell lines tested. These results indicate that TNF-α can enhance the surface expression of HLA-ABC antigens on human glioma cells in the absence of a direct cytotoxic/cytostatic effect.