Multiple antigens related to the major envelope glycoprotein of murine leukemia virus expressed on B16 melanoma cells as targets of host immune response

Abstract

Reactivity of B16 melanoma cell surface proteins with antisera to the major envelope glycoprotein, gp70, of murine leukemia viruses was assessed by radioimmunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Surface proteins from cultured monolayers of the B16 melanoma and variant lines B16-F1, B16-F1(1r6), B16-F10, and B16-F10(1r6), and from purified B16 melanoma tumor cells, contained three glycosylated components specifically reactive with gp70 antisera, with apparent molecular weights of 70,000, 80,000, and 85,000 (B16-gp70, B16-gp80, and B16-gp85). Antisera raised in syngeneic C57BL/6 mice by immunizing with X-irradiated B16, B16-F10, or B16-F10(1r6) cells immunoprecipitated only solubilized B16-gp70, B16-gp80, and B16-gp85. Absorption of mouse antiserum to B16-gp70/80/85 antigens with purified viruses from various sources indicated that antigens on all three molecules were related to endogenous AKR-type murine leukemia virus antigens. Mice hyperimmunized against melanoma cells were challenged subcutaneously with 4 X 10(4), 10(5), or 2.5 X 10(5) viable B16 or B16-F10 cells, inocula that were lethal and nonmetastatic in unimmunized mice. The lowest cell dose was rejected by 90% of immunized mice. Tumors grew in an average of 58% of immunized mice challenged with 10(5) cells, pulmonary metastases occurring in 61% of those mice. Inocula of 2.5 X 10(5) cells grew in all immunized mice, with a 60% incidence of metastasis. These studies indicate that host immunity to B16-gp70/80/85 antigens can either inhibit or stimulate B16 melanoma tumor progression.