Isoform-Specific Transcriptomic Regulation of miR-133A1, miR-133A2, and miR-133B in Colorectal Cancer

Background: MicroRNA-133 (miR-133) has been implicated in diverse cancers as a tumor suppressor, yet the isoform-specific contributions of miR-133A1, miR-133A2, and miR-133B in colorectal cancer (CRC) remain unclear. Methods: We established stable colorectal cancer cell lines expressing each miR-133 isoform and performed iso-form-level transcriptomic profiling. Differentially expressed genes (DEGs) were iden-tified relative to parental cells and subjected to gene ontology (GO) and KEGG en-richment analyses. Comparative analyses highlighted both shared and distinct bio-logical pathways regulated by each isoform. Results: Venn diagram and clustering analyses revealed that all three isoforms shared a core regulatory program, with 34 genes consistently upregulated and 195 genes downregulated across all isoforms, while also displaying isoform-specific DEGs. miR-133A1 and miR-133A2 showed strong transcriptional similarity, predominantly modulating extracellular matrix or-ganization, cell migration, and apoptotic pathways. In contrast, miR-133B exhibited a distinct expression profile, preferentially influencing RNA processing, immune sup-pression, and oncogenic signaling pathways including PI3K-Akt, Hippo, and p53 sig-naling. Heatmap analysis of representative genes confirmed both overlapping and isoform-specific expression changes, with survival- and proliferation-associated genes more strongly upregulated in miR-133A2 and miR-133B. Conclusion: These findings suggest that miR-133 isoforms exert both shared and divergent regulatory functions in colorectal cancer, coordinating apoptosis, proliferation, migration, and signaling net-work modulation. Isoform-specific transcriptional regulation of miR-133 may contrib-ute to tumor progression and represents a potential biomarker and therapeutic target in CRC.