PIM1/NF-κB/CCL2 Blockade Enhances Anti-PD-1 Therapy Response by Modulating Macrophage Infiltration and Polarization in Tumor Microenvironment of NSCLC

Elevated infiltration of tumor-associated macrophages (TAMs) drives tumor progression and correlates with poor prognosis for various tumor types. Our research identifies that the ablation of the Pim-1 proto-oncogene (PIM1) in non-small cell lung cancer (NSCLC) suppresses TAM infiltration and prevents them from polarizing toward the M2 phenotype, thereby reshaping the tumor immune microenvironment (TME). The predominant mechanism through which PIM1 exerts its impact on macrophage chemotaxis and polarization involves CC motif chemokine ligand 2 (CCL2). The expression level of PIM1 is positively correlated with high CCL2 expression in NSCLC, conferring a worse overall patient survival. Mechanistically, PIM1 deficiency facilitates the reprogramming of TAMs by targeting nuclear factor kappa beta (NF-κB) signaling and inhibits CCL2 transactivation by NSCLC cells. The decreased secretion of CCL2 impedes TAM accumulation and their polarization toward a pro-tumoral phenotype. Furthermore, Dual blockade of Pim1 and PD-1 collaboratively suppressed tumor growth, repolarized macrophages, and boosted the efficacy of anti-PD-1 antibody. Collectively, our findings elucidate the pivotal role of PIM1 in orchestrating TAMs within the TME of NSCLC and highlight the potential of PIM1 inhibition as a strategy for enhancing the efficacy of cancer immunotherapy.