Augmentation of tumor targeting in a line of glioma-specific mouse cytotoxic T-lymphocytes by retroviral expression of mouse gamma-interferon complementary DNA.

As an initial approach to experiments directed toward effective adoptive immunotherapy for cancer using lymphokine genes, we transferred retrovirally a complementary DNA encoding mouse gamma-interferon (IFN-gamma) into a specific cytotoxic T-lymphocyte clone, designated E-4, against 203 glioma cells (a 20-methylcholanthrene-induced mouse glioma line) and confirmed the efficacy of IFN-gamma production from the exogenous gene on augmentation of tumor targeting. Of five, two gene-transferred subclones constitutively produced 8 to 10 times the amount of IFN-gamma as compared with the parental E-4. Correspondingly, these two subclones exhibited 2 to 3 times higher killing activity against 203 glioma than the parental cells; the enhancement of the killing activities was abrogated by an adequate addition of anti-IFN-gamma antibody. No alteration was seen after the gene transfer in cell surface phenotypes, Thy-1+, Lyt-1-, Lyt-2+,3+, and asialo-GM1-. The surface expression of a major histocompatibility complex Class I antigen, H-2Kb, was not altered remarkably, but the Class II antigen, I-Ab, was partially and slightly enhanced on the two IFN-gamma-producing sublines mentioned above on fluorescence-activated cell sorter analysis. Since it is considered that in the vicinity of the constitutively IFN-gamma producing cytotoxic T-lymphocyte cells tumor cells are exposed to a high concentration of IFN-gamma, the cells may be stimulated to induce or enhance the expression of surface antigens including major histocompatibility complex antigens as well as tumor-associated antigens relevant to immune recognition. The 203 glioma cells pretreated with IFN-gamma were more efficiently killed by both the parental E-4 and the gene-transferred sublines. Taken together, the results suggested that the augmented specific tumor-killing activity of our gene-transferred cytotoxic T-lymphocytes was ascribed to the constitutive production of IFN-gamma derived from the exogenous gene.