ASH2L‐K312‐Lac Stimulates Angiogenesis in Tumors to Expedite the Malignant Progression of Hepatocellular Carcinoma

Abstract Hepatocellular carcinoma (HCC) is a common malignant tumor. However, the role of lactic acid–modified proteins in its pathogenesis is unclear. This study determines the distribution of a novel post‐translational modification—protein lactylation—in HCC to identify potential targets and obtain mechanistic insights into this disease. Using high‐throughput proteomics, lysine 312 lactylation (K312‐lac) of the Set1/Ash2 histone methyltransferase complex subunit (ASH2L) is revealed as a candidate for further investigation. Subsequently, alanyl‐tRNA synthetase 1 (AARS1) and histone deacetylase 1 (HDAC1) are shown to mediate lactylation modification of ASH2L. In vivo experiments demonstrate that ASH2L‐K312‐lac promotes HCC malignant progression and is positively correlated with tumor microvessel density, and vascular endothelial growth factor A (VEGFA) is identified as the key mediator in ASH2L‐K312‐lac‐induced angiogenesis. High‐throughput sequencing reveals ASH2L‐K312‐lac enrichment in the genome regions encoding VEGFA , facilitating targeted recruitment of the mixed lineage leukemia complex to these loci and enhancing VEGFA expression through synergistic activation of enhancers and promoters. Finally, clinical sample analyses and robust in vivo preclinical experiments identify ASH2L‐K312‐lac as a promising therapeutic target for clinical application. These findings provide a theoretical foundation for the clinical translation of ASH2L‐K312‐lac‐based treatment approaches, offering potential advancements in HCC diagnosis and treatment.