LAUSR

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.