Thuy Tran, Gabriela Athziri Sánchez‐Zuno, Lais Osmani, Jasmine I. Caulfield, Caroline Naomi Valdez, Marta Piecychna, Lin Leng, Michelle E. Armstrong, Seamas C. Donnelly, Carlo Bifulco, Terri Clister, Rajan P. Kulkarni, Lin Zhang, Mario Sznol, Lucia B. Jilaveanu, Harriet M. Kluger, Insoo Kang, Richard Bucala
These findings highlight that the addition of anti-MIF to anti-PD-1 reduces tumor growth, enhances antitumor responses, prolongs survival, and augments key intratumor immune cell populations involved in immune activation against tumors.
Macrophage migration inhibitory factor (MIF) is an upstream regulatory cytokine that is associated with advanced disease and poor outcomes in multiple cancer types, including melanoma. We investigated whether anti-MIF therapy could enhance the antitumor effects of the immune checkpoint inhibitor anti-programmed cell death 1 (anti-PD-1) in 2 murine tumor models. The therapeutic efficacy of anti-MIF, alone or combined with anti-PD-1, was tested in the YUMMER1.7 melanoma and MC38 colorectal cancer models. Tumor growth and survival were assessed in untreated Mif-knockout (KO) and low-expression human MIF allele (CATT5) mice and compared with wild-type (WT) or high-expression MIF allele (CATT7) mice. Tumor-bearing animals underwent cytokine profiling, tumor immunohistochemistry, flow cytometry, and scRNA-Seq. We also correlated functional variant MIF alleles with melanoma incidence and progression in patients. Our results showed that combined anti-MIF and anti-PD-1 significantly reduced tumor growth, improved survival, and promoted tumor regression, accompanied by enhanced TH1 cytokine levels, increased macrophage activation-related cytokines, and increased type 1 conventional dendritic cells. scRNA-Seq analysis revealed an expansion of intratumor Cd74/C1q/Aif1-expressing macrophages, which exhibited an antitumor phenotype, in response to anti-MIF therapy. MIF-KO and CATT5 mice exhibited reduced tumor burdens compared with WT or CATT7 mice alone and in the presence of anti-PD-1. In patients with melanoma, the high-MIF expression genotype (-173C/C) occurred at higher frequencies compared with healthy controls. These findings highlight that the addition of anti-MIF to anti-PD-1 reduces tumor growth, enhances antitumor responses, prolongs survival, and augments key intratumor immune cell populations involved in immune activation against tumors. This approach merits further consideration for clinical trial development.