We have investigated the introduction and expression of the human lL-6 gene in human colorectal carcinoma cells. lL-6 secreted by the transfected HT-29 human colorectal carcinoma cells was shown to be biologically active. Significant enhancement in the expression of CEA, but not in the expression of HLA class l and class II and ICAM-1 antigens, was observed. These results thus suggest another potential role for the use of lL-6 gene transfer in the immunotherapy of human cancers. We also demonstrated an enhancement by recombinant human M-CSF (rhM-CSF) on the ADCC activity of human monocytes using several MAbs. We have investigated the approach of combining tumor-infiltrating lymphocytes and anti-tumor MAbs in the creation of a T cell capable of secreting anti-tumor Ig. The cDNA expression construct of the chimeric D612 heavy chain and light chain genes in retroviral vectors were introduced into MOLT-4 cells. The secreted Ig retained its antigen-binding properties and its ability to mediate ADCC against human tumor cells. We have also investigated whether human T lymphocytes are able to distinguish the determinants of the point-mutated ras p21 proteins from normal ras p21. Cellular immunity to three synthetic peptides representing amino acids 5-17 of mutated ras p21 proteins with an exchange of normal glycine (G12) at position 12 by valine (V12), cysteine (C12) or aspartic acid (D12) was studied. T cell lines specific for peptides V12, C12, and D12 were able to be established from normal peripheral blood lymphocytes. The specificity of the T cell lines were assayed by T cell proliferation and production of cytokines. Cytotoxicity was demonstrated using as targets autologous EBV transformed B cells, pulsed with specific mutated ras peptides, and autologous EBV transformed B cells transfected with a vector carrying ras p21 protein constructs. T cells were MHC class II restricted. The results demonstrated that a human T cell specific immune response to point-mutated ras p21 proteins bearing a single amino acid substitution can be elicited from PBL, suggesting a potential for specific immunotherapy of human cancers.
