Lactylation-Driven NUPR1 Promotes Immunosuppression of Tumor-Infiltrating Macrophages in Hepatocellular Carcinoma

While checkpoint immunotherapy effectively mobilizes T-cell responses against tumors, its success in hepatocellular carcinoma (HCC) is frequently undermined by immunosuppressive myeloid cells within the tumor microenvironment. This study investigates the role of nuclear protein 1 (NUPR1), a gene prominently expressed in tumor-associated macrophages (TAMs), in mediating this suppression and influencing immunotherapy outcomes. Through comprehensive analysis of single-cell RNA sequencing (scRNA-seq) datasets and functional assays in vitro and in vivo, NUPR1 is identified as a critical regulator within TAMs. The upregulation of NUPR1 is associated with enhanced M2 macrophage polarization and increased expression of immune checkpoints PD-L1 and SIRPA, resulting in CD8+ T cell exhaustion and a diminished response to immunotherapy. Mechanistically, NUPR1 inhibits the ERK and JNK signaling pathways, thereby creating an immunosuppressive milieu conducive to tumor progression. Additionally, tumor-derived lactate is shown to upregulate NUPR1 expression in macrophages via histone lactylation, perpetuating a feedback loop that intensifies immune suppression. Pharmacological targeting of NUPR1 reverses M2 polarization, curtails tumor growth, and augments the efficacy of PD-1 blockade in preclinical models, positioning NUPR1 as both a potential biomarker for immunotherapy responsiveness and a therapeutic target to boost immunotherapy efficacy in HCC.