A concurrent canonical and modified miRNAome pan-cancer study on TCGA and TARGET cohorts leads to an enhanced resolution in cancer
MiRNA Epitranscriptomics has placed a new layer of complexity in the cancer field. Despite miRNA editing and shifted miRNA isoforms are gaining attention due to recent improvements in next-generation sequencing, a simultaneous study of both modifications in cancer is still missing. Here, we concurrently profiled multiple miRNA modifications, such as A-to-I RNA editing and shifted miRNA isoforms, in >13K adult and pediatric tumor samples across 38 distinct cancer cohorts from The Cancer Genome Atlas and The Therapeutically Applicable Research to Generate Effective Treatments datasets. We investigated the differences among canonical miRNAs and a wider comprehensive miRNAome from the expression, clustering, dysregulation, and prognostic perspective. Interestingly, the wider miRNAome boosted clustering results, uniquely outlining cohorts' clinical-pathological features. The abundance of expressed miRNA isoforms directly related to the activation/deactivation of critical carcinogenesis pathways. We found dysregulated modified miRNAs characterized by an opposite expression trend than their canonical counterparts in cancer, potentially impacting their targetome and function. Our study emphasizes the importance of modified miRNAs as potential cancer biomarkers and gene expression regulators, outlining once more the importance of going beyond the well-established paradigm of one-mature-miRNA per miRNA arm.