Interleukin-2-secreting Mouse Fibroblasts Transfected with Genomic DNA from Murine Melanoma Cells Prolong the Survival of Mice with Melanoma

A retrovirus was used to introduce a provirus (pZipNeoSVIL-2) containing the gene for interleukin-2 (IL-2) along with a neor gene (confers resistance to G418) into LM cells, a mouse cell line expressing defined major histocompatibility complex class I antigens (H-2k). After initial selection in growth medium containing G418, IL-2 secretion was confirmed, and the cells were then cotransfected with genomic DNA from B16F1 or B16F10 melanoma cells, along with DNA from a plasmid (pHyg) that confers resistance to hygromycin. After a second round of selection in growth medium containing sufficient quantities of hygromycin to kill 100% of nontransfected cells but without further modification, the unfractionated populations of transfected cells were tested for their immunotherapeutic properties in C57BIV6 mice (H-2b) with established B16 melanomas (H-2b). Animals with melanomas treated with either of the transfected cell populations survived significantly (P < 0.01) longer than untreated mice or mice treated with irradiated (5000 rads) B16F1 melanoma cells. The animals also survived longer (P < 0.05) than mice with melanoma treated with IL-2-secreting LM cells transfected with genomic DNA from MOPC-315 cells, a nonimmunologically cross-reactive murine tumor. As determined by the capacity of monoclonal antibodies to T-cell subsets to inhibit the antimelanoma response in a 51Cr release assay, the antimelanoma immunity in mice immunized with cells transfected with genomic DNA from either B16F1 or B16F10 cells was mediated primarily by Lyt-2.2+ T-cells. These data raise the possibility that a generic, live cell tumor vaccine can be developed that can be modified to provide specificity for the neoplasms of individual patients.