Hsa_circ_0020134 promotes liver metastasis of colorectal cancer through the miR-183-5p-PFN2-TGF-β/Smad axis

Circular RNAs (circRNAs) are a distinct class of non-coding RNAs that play regulatory roles in the initiation and progression of tumors. With advancements in transcriptome sequencing technology, numerous circRNAs that play significant roles in tumor-related genes have been identified. In this study, we used transcriptome sequencing to analyze the expression levels of circRNAs in normal adjacent tissues, primary colorectal cancer (CRC) tissues, and CRC tissues with liver metastasis. We successfully identified the circRNA hsa_circ_0020134 (circ0020134), which exhibited significantly elevated expression specifically in CRC with liver metastasis. Importantly, high levels of circ0020134 were associated with a poor prognosis among patients. Functional experiments demonstrated that circ0020134 promotes the proliferation and metastasis of CRC cells both in vitro and in vivo. Mechanistically, upregulation of circ0020134 was induced by the transcription factor, PAX5, while miR-183-5p acted as a sponge for circ0020134, leading to partial upregulation of PFN2 mRNA and protein levels, thereby further activating the downstream TGF-β/Smad pathway. Additionally, downregulation of circ0020134 inhibited epithelial-mesenchymal transition (EMT) in CRC cells, which could be reversed by miR-183-5p inhibitor treatment. Collectively, our findings confirm that the circ0020134-miR-183-5p-PFN2-TGF-β/Smad axis induces EMT transformation within tumor cells, promoting CRC proliferation and metastasis, thus highlighting its potential as a therapeutic target for patients with CRC liver metastasis.