Discovered as inflammatory cytokines, MIF and DDT exhibit widespread expression and have emerged as critical mediators in the response to infection, inflammation, and more recently, in cancer. In this comprehensive review, we provide details on their structures, binding partners, regulatory mechanisms, and roles in cancer. We also elaborate on their significant impact in driving tumorigenesis across various cancer types, supported by extensive in vitro, in vivo, bioinformatic, and clinical studies. To date, only a limited number of clinical trials have explored MIF as a therapeutic target in cancer patients, and DDT has not been evaluated. The ongoing pursuit of optimal strategies for targeting MIF and DDT highlights their potential as promising antitumor candidates. Dual inhibition of MIF and DDT may allow for the most effective suppression of canonical and non-canonical signaling pathways, warranting further investigations and clinical exploration.

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 (CATT ₅ ) mice and compared with wild-type (WT) or high-expression MIF allele (CATT ₇ ) 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 T _H 1 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 CATT ₅ mice exhibited reduced tumor burdens compared with WT or CATT ₇ 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.