snoRNAs and their derived sdRNAs: Emerging regulators, biomarkers, and therapeutic targets in human cancers (Review)

Small nucleolar RNAs (snoRNAs) are a conserved class of non‑coding RNAs that guide 2'‑O‑methylation and pseudouridylation of ribosomal RNA. First identified over five decades ago, snoRNAs have emerged as critical regulators of cellular function, with high‑throughput sequencing revealing their dysregulation in numerous human diseases, particularly cancer. In the present review, the biogenesis, classification, and modification mechanisms of snoRNAs and snoRNA‑derived fragments (sdRNAs) are comprehensively summarized. Recent advances in understanding their non‑canonical functions are highlighted, which extend beyond ribosomal RNA modification to include regulation of mRNA splicing, stability, and protein interactions. These diverse mechanisms enable snoRNAs to influence key cancer‑related processes such as proliferation, metastasis, metabolic reprogramming, and therapy resistance. A comprehensive overview of snoRNA dysregulation across major cancer types is provided, including colorectal, hepatocellular, gastric, lung, breast, and ovarian cancers, with a detailed discussion of underlying molecular pathways. Furthermore, their emerging potential as diagnostic and prognostic biomarkers detectable in liquid biopsies is examined, as well as their promise as therapeutic targets amenable to antisense oligonucleotide and small molecule intervention. The present review integrates current knowledge of snoRNA/sdRNA biology and highlights critical gaps and future directions, providing a foundation for translating these regulatory RNAs into clinical oncology applications.