Mirtrons in Human Cancers

Mirtrons represent a new subclass of microRNAs (miRNAs) that are processed through non-canonical biogenesis pathways. Unlike canonical miRNAs, which require Drosha-mediated cleavage, mirtrons are generated via the splicing of short intronic sequences, bypassing Drosha entirely. While mirtrons are found across a variety of organisms, their conservation between species is relatively low. This evolutionary divergence has resulted in mirtrons acquiring species-specific regulatory functions. In humans, mirtrons remain an understudied group of regulatory RNAs. However, emerging evidence highlights their critical roles in cancer biology. These small RNAs influence a range of oncogenic processes, including tumor initiation, progression, metastasis, and resistance to therapy. By directly regulating the expression of oncogenes and tumor suppressor genes, mirtrons serve as key molecular mediators within cellular signaling pathways. What sets mirtrons apart from canonical miRNAs is their unique mode of biogenesis and structural attributes, which reveal alternative regulatory mechanisms that could be exploited in cancer biology. Recent advances in understanding their functions suggest that mirtrons hold significant potential as biomarkers for cancer diagnosis and prognosis. Additionally, their role as modulators of cancer pathways positions them as promising therapeutic targets in precision oncology. This review delves into the growing body of research on mirtrons, focusing on their biogenesis, biological roles, and implications in cancer. By emphasizing their distinct features and clinical relevance, it aims to provide a comprehensive perspective on the potential applications of mirtrons in advancing cancer diagnostics and therapeutics.