Lactate drives immune resistance via a pharmaceutically reversible H3K18la-KIF20A-c-Myc-PD-L1 axis in hepatocellular carcinoma

Objective: Resistance to immunotherapy, driven by the immunosuppressive tumor microenvironment, remains a major clinical challenge in hepatocellular carcinoma (HCC). Although metabolic reprogramming is a known culprit, the precise epigenetic mechanisms linking lactate accumulation to immune evasion are poorly defined. Methods: Immunohistochemistry analysis of 89 pairs of HCC and paracancerous tissues was conducted to correlate histone h3 lysine 18 lactylation (H3K18la) levels with TNM stage. A separate clinical cohort of 46 patients with HCC was enrolled to assess the association between H3K18la levels and anti-PD-1 therapy resistance. Chromatin immunoprecipitation sequencing in HCC cells, performed to screen for downstream targets, identified kinesin family member 20A (KIF20A). The regulatory relationships among H3K18la, KIF20A, c-Myc, and PD-L1 were verified with dual-luciferase reporter assays and chromatin immunoprecipitation-PCR. The immune evasion mechanism was explored through gene knockdown/overexpression in HCC cells, followed by co-culture with CD8+ T cells and functional analysis via flow cytometry. Finally, a subcutaneous mouse xenograft model was established to evaluate the synergistic efficacy of a glycolysis inhibitor combined with anti-PD-1 therapy on tumor growth and the tumor immune microenvironment. Results: Histone lactylation (forming H3K18la) was identified as a key epigenetic checkpoint linking tumor metabolism to immunotherapy failure in HCC. Elevated H3K18la is a reliable biomarker for tumor progression and resistance to anti-PD-1 therapy. Mechanistically, we discovered that lactate-driven H3K18la directly activates transcription of the oncogene KIF20A. KIF20A in turn stabilizes c-Myc protein, thereby enhancing PD-L1 expression and attenuating anti-tumor immunity. This immunosuppressive phenotype was therapeutically reversible: genetic silencing of KIF20A restored T cell function, and pharmacological inhibition of glycolysis acted synergistically with anti-PD-1 therapy in suppressing tumor growth and extending survival by dismantling the H3K18la-KIF20A axis. Conclusions: This study deciphered a novel druggable metabolic-epigenetic pathway (lactate-H3K18la-KIF20A-Myc-PD-L1) responsible for immune evasion in HCC. Targeting this axis might offer a promising strategy to reprogram the tumor microenvironment and restore immunotherapy sensitivity.