AS (alternative splicing) is a fundamental process by which a gene can generate multiple distinct mRNA transcripts to increase protein diversity. Defects in AS influence the occurrence and development of many diseases, including cancers, and are frequently found to participate in various aspects of cancer biology, such as promoting invasion, metastasis, apoptosis resistance and drug resistance. NcRNAs (noncoding RNAs) are an abundant class of RNAs that do not encode proteins. NcRNAs include miRNAs (microRNAs), lncRNAs (long noncoding RNAs), circRNAs (circular RNAs) and snRNAs (small nuclear RNAs) and have been proven to act as regulatory molecules that mediate cancer processes through AS. NcRNAs can directly or indirectly influence a plethora of molecular targets to regulate cis-acting elements, trans-acting factors, or pre-mRNA transcription at multiple levels, affecting the AS process and generating alternatively spliced isoforms. Consequently, ncRNA-mediated AS outcomes affect multiple cellular signaling pathways that promote or suppress cancer progression. In this review, we summarize the current mechanisms by which ncRNAs regulate AS in cancers and discuss their potential clinical applications as biomarkers and therapeutic targets.

Background: Hepatocellular carcinoma (HCC) with stemness features are pivotal for tumorigenesis, chemoresistance, and progression. Long non-coding RNAs have been implicated in the regulation of HCC stemness features; however, their mechanisms remain largely unknown. Here, we found that Lnc-PDZD7 is a potential oncogene. We systematically analyzed the clinical significance and mechanism of Lnc-PDZD7 in stemness and chemosensitivity regulation. Methods: We analyzed the Lnc-PDZD7 expression levels in liver cancer tissues and cell line by qRT-PCR and In situ hybridization. Gain- and loss-of-function experiments were conducted to investigate the biological functions of Lnc-PDZD7 in stemness and chemosensitivity regulation. Bioinformatics analysis, dual-luciferase reporter assays were performed to validate that Lnc-PDZD7 competitively regulates EZH2, Moreover, chromatin immunoprecipitation assays, bisulfite genomic sequencing and Western blot were performed to evaluate the mechanisms of EZH2 repressing ATOH8. Results: Lnc-PDZD7 is frequently upregulated in HCC tissues. Patients with high Lnc-PDZD7 expression had poorer prognoses and a poor response to adjuvant TACE therapy. Lnc-PDZD7 could promote stemness features and suppress the sensitivity of HCC cells to anticancer drugs in vitro and in vivo. Mechanistically, Lnc-PDZD7 functioned as a molecular sponge for miR-101, antagonizing its ability to repress EZH2 expression. Subsequently, EZH2 can further inhibit the expression of the stemness regulator ATOH8 via elevating its H3K27 trimethylation and DNA methylation. Conclusion: Lnc-PDZD7 promotes stemness properties and suppresses chemosensitivity though the miR-101/EZH2/ATOH8 pathway, providing new biomarkers for diagnosis and potential drug targets for HCC.