NSUN2 Promotes Cancer Immune Evasion via Its Moonlighting Function Acting on Metabolic Reprogramming

Background: Although cancer immunotherapies have revolutionized cancer treatment, a substantial proportion of patients remain unresponsive. Elucidating the molecular mechanisms underlying tumor immune evasion and identifying key regulators are essential for improving immunotherapy efficacy. NOP2/Sun RNA methyltransferase 2 (NSUN2) exhibits widespread mutations across pan-cancer cohorts. This study aimed to delineate the noncanonical functions of NSUN2 in cancer immune modulation and explore its potential as a therapeutic target for cancer immunotherapy. Methods: Multiple cancer cells expressing catalytically inactive NSUN2 mutants were generated and subjected to in vitro functional assays and in vivo studies in immunocompetent mouse models to evaluate their effects on tumor growth and antitumor immunity. Integrative multi-omics analyses, including transcriptomics, metabolomics, and mass spectrometry, were performed to elucidate the molecular mechanisms underlying NSUN2-mediated immune evasion. A proteolysis-targeting chimera (PROTAC) system was developed to achieve targeted degradation of NSUN2, and the clinical relevance of NSUN2 expression in predicting immunotherapy responses was assessed using institutional and public datasets. Results: The enzymatically inactive NSUN2 mutant had minimal effects on tumor cell proliferation in vitro but markedly promoted tumor immune evasion in vivo. Multi-omics analyses revealed that NSUN2 induced metabolic reprogramming and elevated succinate levels, which suppressed cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling in tumor-associated macrophages (TAMs), thereby remodeling the tumor immune microenvironment and promoting M2-like TAM infiltration. Mechanistically, NSUN2 interacted with GATA-binding protein 3 (GATA3) through its methyltransferase domain, relieving GATA3-mediated transcriptional repression of succinate-CoA ligase GDP/ADP-forming subunit α and β genes (SUCLG1 and SUCLG2), leading to succinate accumulation. A newly developed NSUN2-targeting PROTAC demonstrated therapeutic efficacy and safety in combination with cancer immunotherapy. Clinically, low NSUN2 expression was associated with improved immunotherapy responses and survival. Conclusions: Taken together, these findings revealed a noncanonical role of NSUN2 in reshaping the tumor immunosuppressive microenvironment, positioning NSUN2 as a pivotal repressor of cancer immunity and a promising immunotherapeutic target.