Overexpression Of Rab27B In Human Intrahepatic Cholangiocarcinoma: Its Correlation With Invasion And Metastasis Via Enhanced Expression Of Nuclear β-catenin

Backgrounds and objectives Rab27 B,the small GTPase,plays an important role in regulating the transport of multivesicular endosomes and release of exosomes which is involved in modulating invasive growth and metastasis in cancers.This research was designed to explore the association of Rab27 B expression with clinicopathological characteristics and prognosis of intrahepatic cholangiocarcinoma(ICC)and its potential mechanism.Methods The expression of Rab27 B protein was evaluated in 79 intrahepatic cholangiocarcinoma tissues and matched adjacent noncancerous tissues by immunohistochemistry(IHC).The relationship between Rab27 B expression and clinicopathological factors was investigated.Cox regression and Kaplan-Meier survival analyses were executed to evaluate the prognosis of intrahepatic cholangiocarcinoma.Roles of Rab27 B in cell proliferation and invasion of human cholangiocarcinoma cell lines were investigated using CCk-8 assay,scratch assay and Transwell invasion assay.Furthermore,q RT-PCR,western blot and immunofluorescence assay were performed to explore the potential molecular mechanism.Results Rab27 B expression was identified in the cytoplasm and membrane of intrahepatic cholangiocarcinoma cells.Immunoreactive scores of Rab27 B were significantly higher in intrahepatic cholangiocarcinoma tissues than in matched adjacent noncancerous tissues(P<0.05).High expression of Rab27B(immunoreactive score≥4)was detected in 43.0%(34/79)of intrahepatic cholangiocarcinoma tissues and significantly correlated with lymph node metastasis(P=0.004),vascular invasion(P=0.042)and TMN stage(P=0.004).A multivariate analysis suggested that higher Rab27 B protein expression(P=0.039)and multiple hepatic tumors(P= 0.011)were significantly associated with the overall survival of intrahepatic cholangiocarcinoma patients.Furthermore,overexpression of Rab27 B in cholangiocarcinoma cell lines markedly enhanced cell invasion in vitro,accompanied by a typical epithelial to mesenchymal transition(EMT)process with down-regulation of E-cadherin and up-regulation of N-cadherin and Vimentin.In contrast,Rab27 B silencing inhibited cell invasion and reversed EMT.Moreover,Rab27 B reduced β-catenin expression on the cell membrane and increased its nuclear expression which resulted in up-regulation ofβ-catenin target gene such as CD44,c-myc,and MMP-7.Conclusion Higher expression of Rab27 B is detected in intrahepatic cholangiocarcinoma tissues and promotes metastatic activity of cholangiocarcinoma cells through the up-regulation of nuclearβ-catenin.And Rab27 B may be identified as a useful prognostic marker and therapeutic target in intrahepatic cholangiocarcinoma.