Molecular biological role of epithelial splicing regulatory protein 1 in intrahepatic cholangiocarcinoma

Aim Epithelial splicing regulatory protein 1 (ESRP1) regulates tumor progression and metastasis through the epithelial‒mesenchymal transition by interacting with zinc finger E‐box binding 1 (ZEB1) and CD44 in cancers. However, the role of ESRP1 in intrahepatic cholangiocarcinoma (iCCA) remains unclear. Methods Three iCCA cell lines (HuCCT‐1, SSP‐25, and KKU‐100) were analyzed using small interfering RNA to investigate the molecular biological functions of ESRP1 and ZEB1. The association between clinicopathological features and the expression of ESRP1 and ZEB1 in iCCA tissues was analyzed immunohistochemically. Proteomic analysis was performed to identify molecules related to ESRP1 expression. Results ESRP1 expression was upregulated in HuCCT‐1 and SSP‐25 cells. Cell migration and invasion were enhanced, and the expression of ZEB1 and CD44s (CD44 standard) isoforms were upregulated in the ESRP1 silencing cells. Moreover, ESRP1 silencing increased the expression of N‐cadherin and vimentin, indicating the presence of mesenchymal properties. Conversely, ZEB1 silencing increased the expression of ESRP1 and CD44v (CD44 variant) isoforms. Immunohistochemical analysis revealed that a lower ESRP1‐to‐ZEB1 expression ratio was associated with poor recurrence‐free survival in patients with iCCA. Flotillin 2, a lipid raft marker related to epithelial‒mesenchymal transition, was identified as a protein related to the interactive feedback loop in proteomic analysis. Conclusions ESRP1 suppresses tumor progression in iCCA by interacting with ZEB1 and CD44 to regulate epithelial‒mesenchymal transition. Intrahepatic cholangiocarcinoma is the second most common primary liver malignant tumor and has a poor prognosis. This article showed low expression of Epithelial Splicing Regulatory Protein 1 and high expression of zinc finger E‐box binding homeobox 1 promotes tumor progression (cell proliferation, migration, and invasion) in intrahepatic cholangiocarcinoma by changing CD44 isoforms to regulate epithelial‒mesenchymal transition.