MIF signaling disruption in human M2 macrophages induces IL-1β⁺ and IL4I1⁺ TAM phenotypes via p53 and NR4A1 activation

Tumor-associated macrophages (TAMs) are critical drivers of cancer progression and metastasis, with the M2 phenotype being particularly pro-tumorigenic. However, the precise mechanisms governing their differentiation within the tumor microenvironment remain poorly understood. Macrophage migration inhibitory factor (MIF) and its receptor CD74 are known to drive NF-κB activation and establish a metabolically sustained prometastatic state, making this pathway a viable therapeutic target. Understanding how MIF influences macrophage polarization is crucial for developing effective TAM-targeted therapies.

Researchers investigated the role of autocrine macrophage migration inhibitory factor (MIF) signaling in human M2 macrophages. They disrupted this pathway to observe its impact on macrophage differentiation, p53 activity, and the nuclear receptor NR4A1. The study also examined the function of the arachidonic acid-selective acyl-CoA synthase ACSL4 in macrophage survival and cytokine release. Finally, the CDK4/6 inhibitor abemaciclib was tested for its effects on repolarizing TAM-like macrophages and modulating inflammatory signaling.

Human M2 macrophages rely on autocrine MIF signaling to suppress p53 during their M2-like transition. Disruption of this pathway led to activation of p53 and, unexpectedly, the nuclear receptor NR4A1. This activation induced a senescence-like state resembling specific IL-1β⁺ and IL4I1⁺ TAM subsets observed across multiple cancers. These TAM-like macrophages exhibited a transcriptional program primarily driven by NR4A1, mirroring that induced in IL-1β⁺ TAMs by TNF and PGE2. They also upregulated ACSL4, which promoted cell survival and restrained IL-1β release despite elevated IL1B expression. This effect was mediated by inducing the IL4I1⁺ TAM marker CD38, which drove IL-10 production. Mechanistically, ACSL4 preserved the homeostatic function of STING. Loss of ACSL4 resulted in extensive macrophage death and converted STING from a homeostatic regulator into a driver of IL-1 cytokine release. Finally, abemaciclib repolarized TAM-like macrophages toward a more inflammatory phenotype through off-target inhibition of ACSL4. Abemaciclib enhanced inflammatory signaling by modulating ectodomain shedding, increasing TNF while reducing the release of its natural antagonist, TNF receptor II.