Targeting Iron Regulatory Protein 2 in Tumor-associated Macrophages Activates Antitumor Immunity in NSCLC via Modulating SphK1-PD-L1 Axis.

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide. As a predominant immune cell population in the tumor microenvironment (TME), tumor-associated macrophages (TAMs) play a critical role in tumor progression and resistance to immune checkpoint inhibitors (ICIs). TAMs can promote either antitumor immunity or immunosuppression depending on their polarization status. Iron regulatory protein 2 (IRP2) is a key regulator of intracellular iron homeostasis and has been reported to be upregulated in several tumor types. However, the role of IRP2 in the TME remains unclear. This study revealed the previously unrecognized role of IRP2 in NSCLC progression and explored its potential as a TAM-directed therapeutic target linked to programmed death-ligand 1 (PD-L1) regulation. We found that IRP2 skewed TAMs toward an immunosuppressive state that promoted tumor cell proliferation and migration, and limited apoptosis. Furthermore, IRP2 may sustain PD-L1 expression in TAMs by limiting sphingosine kinase 1 (SphK1)-associated lysosomal degradation. In conclusion, our findings identify IRP2-dependent maintenance of the immunosuppressive TAM phenotype as a promising therapeutic target in NSCLC.