IsomiRs and tRNA-derived fragments are associated with metastasis and patient survival in uveal melanoma.

Uveal melanoma (UVM) is the most common primary intraocular malignancy in adults. With over 50% of patients developing metastatic disease, there is an unmet need for improved diagnostic and therapeutic options. Efforts to understand the molecular biology of the disease have revealed several markers that correlate with patient prognosis, including the copy number of chromosome 3, genetic alterations in the BAP1, EIF1AX and SF3B1 genes, and other transcriptional features. Here, we expand upon previous reports by comprehensively characterizing the short RNA-ome in 80 primary UVM tumor samples. In particular, we describe a previously unseen complex network involving numerous regulatory molecules that comprise microRNA (miRNAs), novel UVM-specific miRNA loci, miRNA isoforms (isomiRs), and tRNA-derived fragments (tRFs). Importantly, we show that the abundance profiles of isomiRs and tRFs associate with various molecular phenotypes, metastatic disease, and patient survival. Our findings suggest deep involvement of isomiRs and tRFs in the disease etiology of UVM. We posit that further study and characterization of these novel molecules will improve understanding of the mechanisms underlying UVM, and lead to the development of new diagnostic and therapeutic approaches.