Introduction of miR-3613-3p as a regulator of transforming growth factor-β (TGF-β) signaling pathway in colorectal cancer.

Introduction: Colorectal cancer (CRC) is the second common cancer and the fourth major reason of cancer death worldwide. Dysregulation of intracellular pathways, such as TGF-β/SMAD signaling, contributes to CRC development. MicroRNAs (miRNAs) are post-transcriptional regulators that are involved in CRC pathogenesis. Here, we aimed to investigate the effect of miR-3613-3p on the TGF-β /SMAD signaling pathway in CRC.

Methods & Results: Bioinformatics analysis suggested that miR-3613-3p is a regulator of TGF-Β signaling downstream genes. Then, miR-3613-3p overexpression was followed by downregulation of TGF-βR1, TGF-βR2, and SMAD2 expression levels, detected by RT-qPCR. Additionally, dual luciferase assay supported the direct interaction of miR-3613-3p with 3'UTR sequences of TGF-βR1 and TGF-βR2 genes. Furthermore, reduced SMAD3 protein level following the miR-3613-3p overexpression verified its suppressive effect against TGF-β signaling in HCT-116 cells, detected by western blot analysis. Finally, miR-3613-3p overexpression induced sub-G1 arrest in HCT116 cells, detected by flow cytometry, and promoted downregulation of cyclin D1 protein expression, which was detected by western blotting analysis.

Conclusion: Our findings indicated that miR-3613-3p plays an important role in CRC by targeting the TGF-β/SMAD signaling pathway and could be considered as a new candidate for further therapy investigations.