Abstract
Cancer immunotherapy has transformed oncology, but lasting responses are still limited due to resistance mechanisms within the tumor microenvironment. MicroRNAs (miRNAs) have emerged as critical regulators of immune checkpoint pathways, antigen presentation, T-cell activity, and macrophage polarization. By modulating both tumor-intrinsic and immune cell-intrinsic processes, miRNAs influence the efficacy of immune checkpoint inhibitors, therapeutic vaccines, and adoptive cell therapies. Additionally, circulating and exosomal miRNAs are being investigated as minimally invasive biomarkers to predict patient response and resistance to immunotherapy. Clinical trials of miRNA-based treatments, including mimics and inhibitors, have highlighted both the promise and challenges of translating these molecules into clinical use. Advances in delivery systems, RNA chemistry, and combinatorial strategies are paving the way for their integration into precision immuno-oncology. This review offers a comprehensive overview of the mechanistic, biomarker, and therapeutic roles of miRNAs in cancer immunotherapy, highlighting ongoing clinical progress and prospects.