Protein arginine methyltransferases in cancer: mechanisms, functions, and therapeutic opportunities

Protein arginine methyltransferases (PRMTs) catalyze the methylation of arginine residues on both histone and non-histone substrates, orchestrating cellular processes such as transcriptional regulation, RNA splicing, signal transduction, and DNA damage response. Because dysregulated methylation reprograms epigenetic and post-transcriptional landscapes to promote malignant transformation, aberrant PRMT activity is closely associated with tumorigenesis and cancer progression. Major family members, containing PRMT1, CARM1, PRMT5, and PRMT6, regulate gene expression through site-specific histone methylation, thereby contributing to the transcriptional activation or repression. PRMTs also methylate a wide range of non-histone proteins, including transcription factors, splicing regulators, and signaling intermediates, to coordinate cell cycle progression, DNA repair, and RNA metabolism. Collectively, PRMT-mediated methylation contributes to higher-order cancer phenotypes, including metabolic reprogramming-through modulation of glycolytic flux, lipid biosynthesis, and redox homeostasis-and immune evasion via altered immune signaling and checkpoint pathways within the tumor microenvironment. Recent advances in chemical biology have led to the development of selective PRMT inhibitors, several of which are currently under clinical evaluation. In this review, we provide a comprehensive and integrative overview of PRMT biology, systematically organizing current knowledge from multilayered regulatory mechanisms to downstream oncogenic effects and emerging therapeutic opportunities.