Published online Mar 21, 2015. doi: 10.3748/wjg.v21.i11.3256
Peer-review started: July 20, 2014
First decision: August 15, 2014
Revised: September 2, 2014
Accepted: October 15, 2014
Article in press: October 15, 2014
Published online: March 21, 2015
AIM: To evaluate the prognostic value of high-mobility group box 1 (HMGB1) expression in intrahepatic cholangiocarcinoma (IHCC) and the possible underlying mechanism.
METHODS: Tissue microarray was constructed from 65 IHCC patients. Immunohistochemistry was performed to validate expression of HMGB1 and Vascular endothelial growth factor C (VEGF-C). Real-time PCR and Western blot analyses were used to study transcript and protein levels. The interaction between HMGB1 and VEGF-C was evaluated by siRNA, real-time PCR, and enzyme-linked immuno assays. The correlation between HMGB1 expression and other clinicopathologic parameters was analyzed by χ2 test, and the univariate as well as multivariate analyses were accomplished by Kaplan-Meier method and Cox-regression model, respectively.
RESULTS: Overall, overexpression of HMGB1 was found in 38/65 (58.8%) IHCCs, whereas VEGF-C overexpression was present in 30/65 (46.2%) cases. Overexpression of HMGB1 was significantly correlated with lymphatic microvessel density (P = 0.031, r = 0.268) and VEGF-C expression (P = 0.041, r = 0.254). With univariate analysis, both HMGB1 (P = 0.001) and VEGF-C (P = 0.004) were identified to be significantly associated with overall survival rate. Multivariate analysis indicated that HMGB1 could be served as an unfavorable independent prognostic factor in IHCCs (P = 0.005). siRNA knockdown of HMGB1 inhibited transforming growth factor-β-induced epithelial-mesenchymal transition (EMT) by elevating E-Cadherin expression and reducing expression of N-Cadherin, Vimentin and Snail in RBE cells. Further in vitro study revealed that HMGB1 silencing significantly decreased the level of VEGF-C, whereas the recombinant HMGB1 increased the VEGF-C level in RBE cells (both P < 0.05), which suggested that HMGB1 could promote lymphatic microvessel density, and subsequently lymphatic invasion, via promoting VEGF-C expression.
CONCLUSION: Our results define an important role of HMGB1 in the progression of cholangiocarcinoma, and HMGB1 may serve as a prognostic marker for IHCC patients.
Core tip: Cholangiocarcinoma is a lethal malignancy of the biliary tract, for which novel biomarkers are urgently needed for its management and treatment. This study shows that high-mobility group box 1 (HMGB1) is an independent prognostic factor in intrahepatic cholangiocarcinoma that positively correlates with lymphatic microvessel density and vascular endothelial growth factor C expression. Furthermore, HMGB1 enhances the secretion of vascular endothelial growth factor C and promotes epithelial-mesenchymal transition of RBE cells. Together, these results define an important role of HMGB1 in the progression of cholangiocarcinoma, which may serve as a prognostic marker for intrahepatic cholangiocarcinoma patients.