Antisense oligonucleotide-mediated inclusion of the TRA2β ultraconserved poison exon induces the expression of a lncRNA with anti-tumor effects

Dysregulated expression of oncogenic splicing factors (SFs) occurs in human tumors in part through alterations in splicing of poison exons (PE), highly conserved exons that trigger RNA degradation. TRA2β is one such SF that undergoes PE suppression in tumor cells. Therefore, manipulation of TRA2β-PE can be a promising therapeutic strategy for cancer. Here, we demonstrate that low TRA2β-PE inclusion correlates with decreased patient survival across multiple tumor types. TRA2β-PE-targeting antisense oligonucleotides (ASOs) induce anti-cancer phenotypes and widespread transcriptomic alterations in cell culture models by causing both TRA2β protein knockdown and upregulation of TRA2β-PE-containing transcripts, which act as long-noncoding RNAs (lncRNAs) to sequester nuclear proteins. Finally, we demonstrate efficacy of TRA2β-PE-targeting ASOs in preclinical 3D organoid and in vivo patient-derived xenograft models. Together, this demonstrates that oncogenic SFs can be drugged using PE-targeting ASOs and elucidates a mechanism by which the TRA2β-PE acts both as a regulator of TRA2β protein expression and as a lncRNA that controls cancer cell growth.