Tumor-specific EphA2 receptor tyrosine kinase inhibits anti-tumor immunity by recruiting suppressive myeloid populations in NSCLC

Given the success of both targeted and immunotherapies against cancer, there is increasing utility for identifying targeted agents that also promote anti-tumor immunity. EphA2 is a receptor tyrosine kinase that contributes to tumor growth and metastasis and has been identified as a viable target for many solid cancers. Investigating EphA2s impact on the host immune system may advance our understanding of tumor immune evasion and the consequences of targeting EphA2 on the tumor microenvironment. Here, we examine how tumor-specific EphA2 affects the activation and infiltration of immune cell populations and the cytokine and chemokine milieu in non-small cell lung cancer (NSCLC). Effects of EphA2 overexpression in murine NSCLC cells were evaluated in both in vitro cell viability assays and in vivo tumor models. Tumor immune infiltrate was assessed by flow cytometry. Cytokine and chemokine expression was evaluated using NanoString technology and qRT-PCR. Although EphA2 overexpression in NSCLC cells did not display proliferative advantage in vitro, it conferred a growth advantage in vivo. Analysis of lung tumor infiltrate revealed decreased natural killer and T cells in the EphA2-overexpressing tumors, as well as increased myeloid populations, including tumor-associated macrophages (TAMs). T cell activation, particularly in CD8 T cells, was decreased, while PD-1 expression was increased. These changes were accompanied by increased monocyte-attracting chemokines, specifically CCL2, CCL7, CCL8, and CCL12, and immunosuppressive proteins TGF-{beta} and arginase 1. Our studies suggest EphA2 on tumor cells recruits monocytes and promotes their differentiation into TAMs that likely inhibit activation and infiltration of cytotoxic lymphocytes, promoting tumor immune escape. Further studies are needed to determine the molecular mechanisms by which EphA2 affects the recruitment of these cell types and to test the function of these myeloid cells.