HDAC2 as a therapeutic target in bladder cancer: insights into the altered epigenetic regulation and lysine lactylation

BACKGROUND: The pathogenesis of bladder cancer (BCa) is driven in part by aberrant epigenetic regulation, most notably the dysregulated expression of histone deacetylases (HDACs). As a class I HDAC, HDAC2 is often overexpressed in cancers and promotes malignancy through diverse mechanisms. Given its broad oncogenic role, an in-depth investigation of its specific functions in epigenetic and post-translational regulation within BCa holds significant promise for developing novel precision therapies. METHODS: In vitro functional assays, including CCK-8, colony formation, transwell and apoptotic assays, as well as in vivo assays in a nude mouse subcutaneous tumor model, were performed to assess the oncogenic and drug-resistant effects of HDAC2. RNA-seq and ATAC-seq were employed to analyze the epigenetic regulatory mechanisms of HDAC2. Combined proteome, lactylome and acetylome analysis of control and HDAC2-overexpressing BCa cells were conducted to map the global profiling of protein lysine acetylation (Kac) and lactylation (Kla). RESULTS: In vitro and in vivo experiments confirmed that HDAC2 overexpression significantly promoted proliferation, metastasis and chemoresistance of BCa. Integrated RNA-seq and ATAC-seq analysis revealed that HDAC2 overexpression led to significant epigenetic alternations, and knockdown of its downstream GRIK2 significantly reversed the oncogenic effects of HDAC2. We screened class I HDACs for their impact on Kac and Kla in BCa cells and found that HDAC2 most significantly reduced global Kla levels. Subsequent proteomic analysis of HDAC2-overexpressing cells identified 528 differentially regulated Kla proteins (encompassing 683 sites) and 1,129 differentially regulated Kac proteins (encompassing 1,458 sites). Notably, DHX15 in the splicesome pathway emerged as the most prominent HDAC2-regulated lactylated protein in the absence of concurrent Kac alterations. Moreover, HDAC2 promoted BCa malignancy through the downregulation of DHX15 Kla and the subsequent modulation of RPL9 splicing. CONCLUSION: Collectively, these findings suggest the pivotal role of HDAC2 in epigenetic modulation and lysine lactylation, and underscore HDAC2 as a promising therapeutic target in BCa.