Identification and characterization of a tumor-derived immunosuppressive glycoprotein from murine melanoma K-1735

Abstract

A suppressive immunoregulatory factor (IRF) produced by murine melanoma K-1735 M3 has been identified. Extracts from tissue or cultured cells grown in serum-medium were prepared by 3 M KCl extraction and partially purified by low-salt precipitation. IRF extracted from fresh tumor, cultured cells, and spent medium from the K-1735 cell line suppressed 3H-thymidine incorporation by splenocytes during mitogen stimulation. Cell viability was not impaired by IRF. IRF suppressed splenocyte proliferation, protein synthesis, murine IL-2-mediated blastogenesis, and mixed splenocyte responses. However, in vitro generation of allogenic cytotoxic cells was not suppressed. Significant inhibitory activity could not be extracted from normal tissues. IRF activity was reduced by treatment with proteolytic enzymes and neuraminidase and was bound by lentil lectin, indicating that the factor is a glycoprotein. IRF was heat-stable, yet labile to treatment with acid, base, or 2-mercaptoethanol. Inhibitory activity was partially characterized by preparative isoelectric focusing (pI 3.5-5.8), and the active moiety had a molecular size of 10-12 K according to HPLC. The HPLC-purified active fraction of IRF did not contain the immunosuppressive retroviral antigen p15(E). Splenocytes from animals treated with IRF in vivo demonstrated reduced responses to Con A and PHA in vitro. Suppressor cells were not identified. We have identified a low-molecular-weight glycoprotein from a murine melanoma, which suppresses a variety of immunologic responses in vitro and in vivo. IRF appears to be a potent mediator of tumor-induced immunosuppression in this model.

SANTAVACTM: Summary of Research and Development

“…The role of cell surface antigens in targeted immune responses has been well investigated and reported [16][17][18][19][20][21]. Briefly, cancer cells escape immune surveillance by maintaining a cell surface that lacks immunodominant antigens [21,22] and presents immunosuppressive ones [23][24][25][26][27]. However, the surfaces of cancer cells still show some evidence of antigenicity.…”

Effects of Chemoimmunotherapy with and without Surgery in Murine MBT-2 Bladder Tumor

“…Tumor cells may not only locally produce or induce the formation of soluble immunosuppressive factors [3,4], but they may also in their late growth induce the produc tion of suppressor T cells that are capable of inhibiting the production of cytotoxic T lymphocytes [5]. This can sig nificantly suppress the host's antitumor immune response and remains the major obstacle of successful anticancer immunotherapy.…”

“…How ever as a tumor progressively grows, it may induce deteri oration of the host's antitumor immune response [1,2] by secreting soluble immunosuppressive factors locally [3,4] and inducing the production of suppressor T cells systemically [5], Theoretically, treatments that either eliminate the tumor-induced immunosuppression or augment the host's tumor-specific immune response may be applied either singly or in combination as the armature for anti cancer therapy. Cyclophosphamide (CYC) has been…”

Production of a Suppressor of Lymphocyte Proliferation by Two Human Oral Carcinoma Cell Lines

“…hortnones [14,23] and irnmune complexes [24]. In cases where "soluble factors' have been examined, however, they appear to have widely diHering properties with molecular weights ranging from <1000 to > 2,000,000 in different systems [25,26]. The picture is further confused by the potential for artefaetual results such as the direct interaction of milogens and thymidine in lymphocyte proliferation a.ssays [ 11].…”