Abstract
BACKGROUND: Long non-coding RNAs (lncRNAs) play crucial roles in cancer pathogenesis, including colorectal cancer (CRC). Distinct lncRNA transcripts from the same gene show diverse regulatory roles in cancer. The MIR100HG, a lncRNA gene characterized by multiple transcript variants, has been implicated in promoting CRC oncogenesis. However, the specific functions of individual MIR100HG transcripts in tumorigenesis remain unclear. METHODS: We explored the MIR100HG transcripts upregulated by TGFβ1 treated in CRC cells using RNA-Seq and characterized a novel transcript in CRC cells and tumor tissues via qRT-PCR. Chromatin immunoprecipitation and luciferase assays revealed this transcript's upstream regulation. Functional experiments were performed in vitro and in mouse models. The molecular mechanism was elucidated through RNA-seq, RNA pull-down, mass spectrometry, RNA immunoprecipitation and co-immunoprecipitation. Finally, we evaluated the transcript's therapeutic potential by treating mouse model tumors with antisense oligonucleotide. RESULTS: We identified a novel transcript, MIR100HG-L, which retains more portion of exon 1 compared to the previously reported shorter transcript. MIR100HG-L was transcriptionally upregulated by TGFβ/SMAD signaling and exhibited elevated expression in CRC tissues. Functionally, this transcript was demonstrated to promote CRC cell proliferation, suppress apoptosis and enhance drug resistance. Mechanistically, MIR100HG-L specifically interacted with BCLAF1, serving as a protein scaffold to connect BCLAF1 with splicing factors. This interaction significantly induced BCLAF1-mediated splicing events of oncogenes related to apoptosis and DNA damage response, enhancing their expression and contributing to CRC development. MIR100HG-L-targeted antisense therapy reduced tumor growth and increased cetuximab sensitivity. CONCLUSIONS: Our study reveals a novel MIR100HG transcript induced by TGFβ/SMAD signaling and explores its distinct oncogenic mechanism through a structure-specific interaction with the BCLAF1. These findings suggest distinct MIR100HG transcripts may exert diverse functions and lead to the identification of novel molecular markers and therapeutic targets for CRC.