Targeted inhibition of the H3K27ac/OGT/O-GlcNAcylation axis to overcome gemcitabine-induced chemotherapy resistance in bladder cancer

Gemcitabine (Gem), a primary treatment for advanced and metastatic bladder Cancer, can lead to malignant progression and drug resistance, though the underlying mechanisms are not fully understood. Post-translational modifications (PTMs) are key to understanding this resistance and identifying new chemosensitizers. To decipher the relationship between the PTM and Gem-induced chemotherapy resistance in bladder Cancer, a Gem-resistant cell line was developed from Gem-sensitive cells through repeated exposure to the drug, revealing increased levels of acetylation and O-GlcNAcylation compared to the parent cells. Thereafter, considering the significant role of histone acetylation in gene regulation, the Histone Acetyltransferase Inhibitor C646 was employed to inhibit growth of Gem-resistant bladder Cancer cells. Intriguingly, C646 was found to prevent the progression of Gem-resistant bladder Cancer not only by inhibiting acetylation but also O-GlcNAcylation modifications both in vitro and in vivo. Immunohistochemistry analysis of bladder Cancer clinical specimens confirmed that both histone H3 lysine 27 acetylation (H3K27ac) and O-GlcNAc transferase (OGT) expression levels were elevated post-chemotherapy and positively correlated. Further, chromatin immunoprecipitation followed by quantitative reverse transcription polymerase chain reaction (ChIP-qPCR) demonstrated that H3K27ac influences OGT expression by binding to its promoter region. Additionally, C646 disrupted OGT-mediated O-GlcNAcylation by suppressing the acetylation of H3K27 and its accumulation on the OGT promoter, thereby inhibiting Gem-resistant bladder Cancer growth. Consequently, targeting the H3K27ac/OGT axis with Histone Acetyltransferase Inhibitor offers a promising strategy to overcome Gem resistance in bladder Cancer.