Immune cell responses to combined treatment of murine melanoma with ALT-803 and Sunitinib in normal and chronic alcohol consuming mice (TUM2P.1032)

Abstract

The immune enhancing IL-15 super agonist ALT-803 and Sunitinib, a tyrosine kinase inhibitor that inhibits immunosuppressive myeloid derived suppressor cells (MDSC) and T regulatory (Treg) cells, were examined for their single and combined effects on immune cell phenotype in normal and chronic alcohol consuming (CAC) mice inoculated with s.c. B16BL6 melanoma. ALT-803 alone and in combination with Sunitinib initially increased CD8+CD44hi and CD8+CD44hiCD62Llo memory phenotype T cells in the spleen and PBL. IFN-γ producing CD8+CD44hi T cells increased in the spleen and the increase was more robust in CAC versus normal mice. These responses decayed during the later stages of tumor growth, and declined more rapidly in the CAC mice. Sunitinib alone did not affect CD8+ T cells or their IFN-γ production. Sunitinib alone and in combination with ALT-803 prevented the increase in CD11b+Gr-1int MDSC in the spleen associated with no treatment or ALT-803 treatment in normal mice; however, the effect was less pronounced in CAC mice where MDSC did not increase in the untreated group over time. MDSC in the PBL increased over time in untreated and ALT-803-treated normal mice. Sunitinib prevented this increase until the late stages of tumor progression. Sunitinib alone and in combination suppressed CD4+CD25+FoxP3+ Treg cells in the spleen during tumor progression.