Antibody targeting of tumor associated macrophages in lung cancer remodel the tumor microenvironment and revives immune targeting of tumor cells

• Immunotherapy for cancer has revolutionized clinical practice and enabled cures for previously lethal cancers. However, the clinical responses are variable and highly influenced by immune regulatory compartments in the tumor microenvironment. This is especially true for immune-excluded tumors, where clinical trials aiming to recover T cell anti-tumor activity have been disappointing. Thus, in NSCLC and other cancers there is a clinical need for additional and combinatory treatments. We have previously shown that antibodies targeting scavenger receptors expressed on tumor-associated macrophages (TAMs), reduces tumor growth and impair metastasis in murine cancer models. Here we investigated targeting of the scavenger receptor MARCO on human TAMs in NSCLC. We found that expression of this receptor in the tumor correlated with immune-exclusion phenotype. Also, we found that lung cancer cell lines converted healthy myeloid cells towards TAM like cells with high expression of MARCO. These human MARCO+ myeloid cells stopped cytotoxic T cells and natural killer (NK) cells from killing tumors and inhibited their overall activity. We then generated anti-human MARCO antibodies and found that these could repolarize TAMs leading to augmented cytolytic ability of NK cells and T cells to kill tumor cells and recovered their proliferation and IFNγ production capacity. Overall, our data demonstrate that it is feasible to use antibodies to alter human TAM immune suppression of NK and T cell anti-tumor activities.

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