Bladder cancer (Bca) is the tenth most common malignant tumor globally, with approximately 500,000 new cases and 200,000 deaths reported each year (Geynisman et al., 2022, Lenis et al., 2020, Li et al., 2023). Approximately 75% of cases are non-muscle invasive, while the remainder are muscle-invasive (Lenis et al., 2020). Despite active treatment, the five-year survival rate for muscle-invasive cases is only 20-40%, and almost 50% exhibit metastasis within three years (Jiang et al., 2021, Zhang et al., 2021). Cisplatin-based combination chemotherapy is the primary treatment approach for metastatic Bca, yet, only 35% of patients initially respond to cisplatin therapy, and the majority of patients who are initially sensitive to cisplatin eventually develop resistance (Lenis et al., 2020, Li et al., 2023). There is an urgent need to identify the factors underlying cisplatin resistance and potential clinical targets is urgently needed.

The primary mechanisms of cisplatin resistance that are currently recognized include the increased efflux of cisplatin, intracellular inactivation of cisplatin, and abnormal DNA damage repair and so on (Jiang et al., 2021, Li et al., 2023). However, targeting just one of these mechanisms is not sufficient to overcome cisplatin resistance (Li et al., 2023). In recent years, accumulating evidence has indicated the pivotal role of epigenetic regulation in the acquisition of cisplatin resistance in cancer cells (Li et al., 2023). Various epigenetic regulatory mechanisms, such as DNA or RNA methylation, and post-translational modifications (PTMs) of histone, contribute to the up-regulation of drug efflux proteins expression in cancer cells or alternatively diminish the expression of drug uptake proteins, thereby circumventing the antitumor effects of cisplatin. Further in-depth investigation is warranted to explore the epigenetic regulatory mechanisms underlying cisplatin resistance.

Recently, a novel PTM known as lactylation, which involves the addition of lactyl groups to lysine residues in protein, has attracted considerable attention. Even under fully aerobic conditions, cancer cells, including those that are drug-resistant, generate lactate and adenosine triphosphate through glycolysis, a phenomenon known as the Warburg effect (Zhang et al., 2019). Accumulated lactate is not merely a metabolic waste product; rather, it serves as a multifunctional bio-signaling molecule that regulates various biological effects including tumor proliferation, metastasis, anti-inflammation, immune modulation, and gene expression (Doherty and Cleveland, 2013, Li et al., 2022a, Li et al., 2022b, Li et al., 2022c). Lactylation has been observed extensively on proteins in cancer cells, particularly on histones (Zhang et al., 2019). Histone lactylation can activate downstream gene transcription and participate in the regulation of tumor development, inflammation, angiogenesis, and macrophage polarization (Xiong et al., 2022, Yang et al., 2022, Yu et al., 2021a). Nevertheless, the involvement of lactylation in cisplatin resistance has not been thoroughly investigated yet.

The advancement of single-cell RNA sequencing (scRNA-seq) technology has presented unprecedented opportunities for the identification of distinct cancer cell populations and their markers (Sun et al., 2022, Zhao et al., 2021). Exploring the heterogeneity of resistant cells and their tumor environment can reveal the mechanisms of resistance and identify individualized treatment targets. In this study, scRNA-seq data from Bca were analyzed to identify and characterize cisplatin-resistant epithelial cells clusters. Cisplatin-resistant epithelial cells undergo metabolic alterations, showing an increased reliance on glycolysis, and up-regulation of lactylation in cisplatin-resistant epithelial cells. Furthermore, we conducted a screening for transcription factors driving cisplatin resistance in Bca and elucidated their roles in the development of resistant cells. A substantial body of evidence indicates that transcription factors play important role in cisplatin resistance, affecting processes such as DNA damage repair, enhanced drug efflux, and others factors (Sun et al., 2019, Torigoe et al., 2005).

Briefly, we unveiled the heterogeneity of cisplatin-resistant epithelial cells in Bca and elucidated the role of lactylation in cisplatin resistance. Specifically, we observed that lactylation was enriched in the promoter regions of these transcription factors, activating their transcription and thereby contributing to cisplatin resistance. Our findings provided novel insights into the underlying mechanisms of cisplatin resistance.