Eliciting effective antitumor immune responses in patients who fail checkpoint inhibitor therapy is a critical challenge in cancer immunotherapy, and in such patients, tumor-associated myeloid cells and macrophages (TAMs) are promising therapeutic targets. We demonstrate in an autochthonous, poorly immunogenic mouse model of melanoma that combination therapy with an agonistic anti-CD40 mAb and CSF-1R inhibitor potently suppressed tumor growth. Microwell assays to measure multiplex protein secretion by single cells identified that untreated tumors have distinct TAM subpopulations secreting MMP9 or cosecreting CCL17/22, characteristic of an M2-like state. Combination therapy reduced the frequency of these subsets, while simultaneously inducing a separate polyfunctional inflammatory TAM subset cosecreting TNF-α, IL-6, and IL-12. Tumor suppression by this combined therapy was partially dependent on T cells, and on TNF-α and IFN-γ. Together, this study demonstrates the potential for targeting TAMs to convert a “cold” into an “inflamed” tumor microenvironment capable of eliciting protective T cell responses.

在检查点抑制剂治疗失败的患者中提高有效的抗肿瘤免疫反应是癌症免疫治疗中的关键挑战，在这类患者中，肿瘤相关的髓样细胞和巨噬细胞（TAM）是有希望的治疗靶点。我们在黑色素瘤的本地化，免疫原性差的小鼠模型中证明，与激动性抗CD40 mAb和CSF-1R抑制剂联合治疗可有效抑制肿瘤生长。用微孔测定法测量单个细胞的多重蛋白分泌，发现未经处理的肿瘤具有分泌MMP9或共同分泌CCL17 / 22的独特TAM亚群，这是M2样状态的特征。联合疗法降低了这些亚群的频率，同时诱导了一个共同分泌TNF-α，IL-6和IL-12的单独的多功能炎性TAM亚群。通过这种联合疗法抑制肿瘤部分依赖于T细胞以及TNF-α和IFN-γ。总之，这项研究证明了靶向TAMs能够将“冷”转变为“发炎”的肿瘤微环境，从而引发保护性T细胞反应的潜力。