MicroRNAs: Novel clinical biomarkers for cancer radiotherapy (Review).

MicroRNAs (miRNAs/miRs) have attracted increasing attention as biomarkers and therapeutic agents for cancer treatment, particularly in the context of radiotherapy. Originally identified >30 years ago, miRNAs are short, non‑coding RNA molecules that regulate gene expression by binding to target mRNAs. Their involvement in physiological processes such as cell cycle regulation, DNA repair, apoptosis and signal transduction makes them essential for modulating cancer cell responses to therapeutic interventions. Recent research has explained the dual role of miRNAs in tumorigenesis. Some miRNAs function as oncogenes, promoting tumor growth and resistance to treatment, while others act as tumor suppressors, enhancing radiosensitivity and promoting apoptosis in cancer cells. Because of their stability, specificity and presence in bodily fluids, miRNAs are promising non‑invasive biomarkers for the diagnosis, prognosis and monitoring of therapeutic responses in cancer. Furthermore, miRNAs such as miR‑144, miR‑200c and let‑7 have demonstrated potential in guiding radiotherapy for breast, prostate, lung and other cancers, modulating treatment outcomes by enhancing radiosensitivity or contributing to radioresistance. Despite the early challenges of miRNA‑based therapies, advancements in miRNA delivery systems, including TargomiR‑ and liposome‑based approaches, offer promising avenues for clinical applications. The present review highlights the role of miRNAs as biomarkers and modulators in cancer radiotherapy and discusses ongoing research on miRNA delivery mechanisms to improve therapeutic outcomes. Future studies are needed to address the challenges of miRNA pleiotropy and safety in clinical applications, to advance miRNA‑based interventions in precision oncology, and to enhance the efficacy of radiotherapy across various cancer types.