Pakistan Journal of Pharmaceutical Sciences

Abstract: Background: Hepatocellular carcinoma (HCC) is characterized by profound metabolic reprogramming and an immunosuppressive tumor immune microenvironment (TIME). Lactate accumulation has recently been implicated in protein lactylation and tumor progression, but its role in reshaping the TIME in HCC remains incompletely understood. Objectives: To investigate how lactate-related metabolic reprogramming influences global protein lactylation and the TIME in HCC. Methods: We integrated high-throughput RNA sequencing, construction of a lactate metabolic process activity (LMPA) model, molecular subtyping, survival analysis and single-cell RNA sequencing to characterize lactate-associated alterations in HCC. Tissue microarrays and in vitro functional assays were used to validate key findings. Results: Elevated expression of lactate dehydrogenase A (LDHA), a core enzyme in lactate metabolism, was significantly associated with altered transcriptional profiles, unfavorable survival and changes in TIME composition in patients with HCC. In vitro, LDHA overexpression promoted HCC cell proliferation, migration and invasion. Patients with high LMPA exhibited significantly poorer prognosis and distinct immune infiltration patterns, including altered proportions of B cells, CD4+ T cells, neutrophils, macrophages, and dendritic cells. Single-cell RNA sequencing further revealed heterogeneous LMPA patterns across cell populations and increased global protein lactylation, particularly in immune cells. In addition, LMPA-based molecular subtypes were closely associated with lactylation-related features. LDHA expression, HDAC2 expression and metastasis were identified as significant prognostic factors. Conclusion: Lactate-related metabolic reprogramming may enhance global protein lactylation and remodel the TIME in HCC, thereby promoting tumor progression. These findings highlight the potential of targeting lactate metabolism and lactylation-associated pathways as novel therapeutic strategies for HCC.