Abstract 4133: The in vitro melanoma tumor microenvironment conditions macrophages to an immunosuppressive M2-like phenotype, which is reversible by oncolytic virus ORCA-010 with immune modulators

Abstract

Abstract The melanoma tumor environment suppresses the immune reaction, favoring tumor escape from the immune system. This suppressive environment is in part sustained by tumor associated M2-like macrophages. In order to activate the immune system, one approach is macrophage-targeted therapies, that repolarize M2-like macrophages to M1-like macrophages. ORCA-010 is a potency enhanced, replication selective oncolytic adenovirus, with strong anti-tumor activity. As a model of macrophage polarization in the tumor microenvironment, human melanoma cell lines were co-cultured in vitro with CD14+ monocytes. The effects to induce M1-like macrophages by addition of lipopolysaccharide (LPS) and interferon (IFN)-gamma, JAK2 or p38 MAPK inhibitors combined with ORCA-010, was assessed in the co-cultures. Cell phenotypes were characterized by flow cytometry. Our data demonstrate that ORCA-010 significantly reduces M2-like macrophage marker CD163 on CD45+ cells in co-cultures, and increases co-stimulatory M1-like macrophage markers CD80 and CD86 expression on macrophages. CD80 is significantly up-regulated by ORCA-010 with LPS and IFN-gamma. Next, the macrophage polarizing effects of combining ORCA-010 with p38 MAPK and JAK2 inhibitors, known for their favorable myeloid M1 and dendritic cell skewing properties, were assessed in the melanoma co-cultures. The inhibitors JAK2 (AG490) and p38 MAPK (LY2228820) both significantly reduced CD163 levels, however did not induce increased CD80 and CD86 by themselves. Only when combining these with ORCA-010 did we observe a CD86 up-regulation. In a B16.OVA immunocompetent mouse model, ORCA-010 appeared to enhance recruitment of CD8+ T cells to the tumor. Interestingly, combining ORCA-010 with anti-PD-1 resulted in a significant increase of recruitment of CD8+ T cells at the tumor, which could be further enhanced by co-treatment with a p38 inhibitor. Our data suggest that ORCA-010 induces a repolarization of the M2-like macrophages to a favorable M1-like phenotype. This can be further enhanced by the combined administration of ORCA-010 with a TLR4 agonist and IFNγ, or with a JAK2 inhibitor. This work is supported by the European Union Horizon2020 ITN-EID grant 643130 “VIRION”. Citation Format: Ioanna E. Milenova, Rieneke van de Ven, Wenliang Dong, Victor W. van Beusechem, Tanja D. de Gruijl. The in vitro melanoma tumor microenvironment conditions macrophages to an immunosuppressive M2-like phenotype, which is reversible by oncolytic virus ORCA-010 with immune modulators [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4133.