EIF4A3/circPTGR1/miR-4725-5p positive- feedback loop promotes colorectal cancer progression via FAK/AKT signaling pathway

BACKGROUND: Colorectal cancer (CRC) is one of the most common malignancies, but the molecular mechanisms underlying CRC progression are not well-understood. Accumulating evidence suggests that circular RNAs (circRNAs) play important roles in genesis and development of cancer. However, the roles and molecular mechanisms of circRNAs in CRC remain largely unelucidated. METHODS: The differential expression patterns of circRNAs between primary CRC tumor tissues and corresponding liver metastases were profiled by RNA sequencing. Associations between circPTGR1 expression and clinicopathological features as well as prognosis were analyzed among CRC patients. The effect of circPTGR1 on CRC growth and metastasis was explored through in vitro, in vivo—comprising subcutaneous xenograft, tail-vein lung metastasis, and intrasplenic liver metastasis models—and notably, patient-derived organoid (PDO) assays. The reciprocal regulation among circPTGR1, miR-4725-5p, and EIF4A3, together with the interaction between miR-4725-5p and FAK (Focal Adhesion Kinase), was predicted by bioinformatic analyses and subsequently validated using qRT-PCR, western blotting, RNA immunoprecipitation (RIP), and dual-luciferase reporter assays. Further confirmation of these regulatory interactions was performed in clinical CRC tissues, PDOs, and xenograft models by qRT-PCR, western blotting, and immunohistochemistry (IHC). RESULTS: Expression of circPTGR1 was significantly upregulated in CRC and elevated circPTGR1 was associated with poor prognosis in CRC patients. In vitro and in vivo experiments demonstrated that circPTGR1 promoted the growth, migration, invasion, and metastasis of CRC. The role of circPTGR1 in enhancing CRC cell proliferation and invasiveness was confirmed utilizing PDO models. Mechanistically, circPTGR1 acted as a molecular sponge for miR-4725-5p, leading to upregulation of its target FAK and consequently activating the FAK/AKT signaling pathway. Importantly, EIF4A3 was identified as a promoter which facilitated the biogenesis of circPTGR1 and a direct downstream target of miR-4725-5p. These findings were validated through clinical CRC tissues, PDO models, and xenograft assays, supporting a novel positive feedback loop involving EIF4A3, circPTGR1, and miR-4725-5p in CRC progression via activating the FAK/AKT signaling pathway. CONCLUSIONS: EIF4A3/circPTGR1/miR-4725-5p positive feedback loop accelerates CRC proliferation and metastasis by activating the FAK/AKT signaling pathway. Therefore, circPTGR1 could serve as a potential prognostic indicator and therapeutic target for CRC.