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).Realtime PCR and Western blot analyses were used to study transcript and protein levels.The interaction between HMGB1 and VEGF-C was evaluated by si RNA,real-time PCR,and enzyme-linked immuno assays.The correlation between HMGB1 expression and other clinicopathologic parameters was analyzed byχ2 test,and the univariate as well as multivariate analyses were accomplished by Kaplan-Meier method and Coxregression 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.Multivariateanalysis indicated that HMGB1 could be served as an unfavorable independent prognostic factor in IHCCs(P=0.005).si RNA knockdown of HMGB1 inhibited transforming growth factor-β-induced epithelialmesenchymal 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 HMGB1increased 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. 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 analyzes were used to study transcript and protein levels. The interaction between HMGB1 and VEGF-C was evaluated by si RNA, real-time PCR, and enzyme-linked immuno assays.The correlation between HMGB1 expression and other clinicopathologic parameters was analyzed byχ2 test, and the univariate as well as multivariate analyzes were performed by Kaplan-Meier method and Cox regression model, respectively .RESULTS: Overall, overexpression of HMGB1 was found in 38/65 (58.8%) IHCCs, 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 rate.Multivariate analysis indicated that HMGB1 could be served as an unfavorable independent prognostic factor in IHCCs (P = 0.005). si RNA knockdown of HMGB1 programmed transforming growth factor-β-induced epithelialmesenchymal transition (EMT) by elevating E-Cadherin expression and reducing expression of N-Cadherin, Vimentin and Snail in RBE cells. Future in vitro study revealed that HMGB1 silencing significantly decreased the level of VEGF-C, whereas the suggested HMGB1 increased by 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 pa tients.