Lymphokine-mediated immunotherapy studies in mouse tumor systems

Studies have been performed using two subcutaneously implanted mouse tumor models to investigate the immunotherapeutic potential of lymphokine-containing culture supernatants from long-term human lymphoblast cell cultures. Human lymphoblastoid cell line, RPMI 1788, was used as a cell culture source of lymphokines. Supernatants were removed from cultures at the stationary phase of growth and concentrated on Amicon filters retaining molecules above 10,000 Daltons. This concentrate was applied to a Sephadex G-25 column, equilibrated with ammonium bicarbonate buffer, for removal of salts and dye from the culture medium. The effluent was lyophilized and reconstituted for use in further purification by affinity chromatography and SDS-PAGE gels. Such preparations were used to inject DBA/2 mice bearing subcutaneous L-1210 tumors. In addition, the B-16 melanoma was used as a model of a solid tumor in C57Bl/l mice. Animals were treated intralesionally and intraperitoneally with lymphokines containing preparations and control solutions. Tumors growing subcutaneously were susceptible to lymphokine-induced inflammation-mediated regression without additional therapy. In the study of L-1210 subcutaneous tumors, reduction in tumor size was followed by complete regression, prolonged survival, immunity to additional inoculation, and cures in 20--40% of the treated mice. Tumor regression and prolongation of survival were also noted in mice bearing B-16 melanomas. These studies support the use of mouse tumors as bioassays for antitumor inflammatory activity of human lymphokine preparations and help to quantitate their potential use in human tumor immunotherapy.