Abstract
BACKGROUND: The tumour microenvironment (TME) significantly influences intercellular communication, with several secreted factors activating both tumour cells and fibroblasts. Connexin43 (Cx43), a crucial gap junction protein, exhibits a significant regulatory role in tumourigenesis; however, the underlying regulatory mechanisms in colorectal cancer (CRC) are not fully understood. METHODS: Transwell co-culture system was utilized to evaluate fibroblast-mediated effects on CRC cells. Immunohistochemical analysis was conducted on clinical specimens. Cell migration and invasion capabilities were measured using Transwell assays. Subcellular localization was assessed via immunofluorescence. Protein interactions were validated by co-immunoprecipitation. RESULTS: The Wnt signalling pathway was activated in the co-culture of CRC cells and fibroblasts. Nuclear Cx43 upregulation was detected and confirmed as a pro-oncogenic factor via prognostic analysis of patient samples. Therefore, although Cx43 on the cell membrane serves as a tumour suppressor, the nuclear translocation of Cx43 has an important influence on the Wnt signalling pathway and promotes CRC progression. Nuclear translocation of Cx43 during malignant progression has a significant effect on metastasis and is regulated by secreted TGF-β. Distinct nuclear translocation patterns of Cx43 observed across CRC cell lines suggest potential regulation by S368 phosphorylation. Co-immunoprecipitation confirmed Cx43/β-catenin interaction, revealing its role in facilitating β-catenin nuclear accumulation. CONCLUSION: We systematically identified nuclear Cx43 as a factor promoting CRC progression. These findings highlight the novel mechanism involving the nuclear translocation of Cx43 as a promoting factor in CRC progression, and enhance our understanding of the interplay between the TME and CRC progression.