Effect of environmental factors on chemoresistance of HepG2 cells by regulating hypoxia-inducible factor-1α / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Accumulating evidence demonstrates that the microenvironment of the host has an important effect on the chemoresistance of tumors. We also found that the formation of intrinsic multidrug resistance is related to environmental factors that are common with tumor growth of hepatocellular carcinoma. The aim of this study was to explore the molecular mechanisms by which multidrug resistance of hepatocellular carcinoma is induced by the microenvironment. In particular, the regulation of nuclear transcription factor (hypoxia-inducible factor-1α, HIF-1α) activation in the process of multidrug resistance formation was investigated.</p><p><b>METHODS</b>HepG2 cells were exposed to different microenvironmental conditions respectively, such as hypoxia, stimulation of glucose deprivation and transfection of plasmid PcDNA3/HBx. In the HepG2 cells, the expression of the related MDR proteins, HIF-1α protein expression and localization, activity of extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) were detected. Specific inhibitor U0126 was used to block ERK/MAPK signal pathway, the alteration of HIF-1α and the related MDR proteins were investigated. Multivariate analysis of variance (MANOVA) repeated measures and one-way analysis of variance (ANOVA) followed by Tukey test or t-test were used to determine differences over time and effects of the treatments.</p><p><b>RESULTS</b>The above three microenvironment factors increase the expression of the related MDR proteins (including P-gp, LRP, and MRP1) and induce MDR of HepG2 cells. HIF-1α was induced at the protein and mRNA levels and the nuclear translocation was also increased. The activity of ERK/MAPK was also increased in HepG2 cells. But when ERK/MAPK pathway was inhibited, the mRNA and protein expression of MDR1, MRP1, and LRP was to some extent decreased. Inhibition of ERK/MAPK significantly reduced activated HIF-1α protein and the nuclear translocation of HIF-1α, whereas HIF-1α mRNA levels were not affected.</p><p><b>CONCLUSIONS</b>The microenvironmental factors could induce MDR of HepG2 cells by the activity of HIF-1α. The activity of HIF-1α is regulated by the ERK/MAPK pathway at the phosphorylation level. As an important nuclear transcription factor, HIF-1α controls the transcription of MDR-related genes and the synthesis of their corresponding proteins by ERK/MAPK signal pathway in HepG2 cells.</p>

The effect of different hepatic vascular exclusion for massive hemorrhage in hepatectomy / 中华外科杂志

<p><b>OBJECTIVE</b>To analyze the effect of different hepatic vascular exclusions for massive hemorrhage in hepatectomy.</p><p><b>METHODS</b>The clinical data of 2238 cases with hepatectomy treated from January 1995 to August 2009 was analyzed retrospectively in the cause of massive hemorrhage (blood loss ≥ 1000 ml), blood loss during liver resection and massive hemorrhage incidence with different methods of hepatic vascular exclusion.</p><p><b>RESULTS</b>Among 2238 cases received hepatectomy, 215 cases (9.6%) had massive hemorrhage because of portal vein tumor thrombus extraction (26.0%), extensive adhesions around the tumor (24.7%), section of liver hemorrhage (23.7%), hepatic vascular injury (15.8%), and tumor rupture (9.8%). Among 2182 cases received hepatectomy without portal vein tumor thrombus extraction, 159 cases (7.3%) had massive hemorrhage, 1257 cases (57.6%) which blood loss were less than 400 ml. Hepatectomy with different hepatic vascular exclusion methods had different blood loss and massive hemorrhage incidence.</p><p><b>CONCLUSION</b>Pringle combined with clamping infrahepatic vena cava method and the liver double-hanging maneuver through the retrohepatic avascular tunnel on the right of the inferior vena cava method can reduce blood loss and massive hemorrhage incidence in hepatectomy more effectively, especially for huge liver tumor resection.</p>

Study on virtual liver surgery planning applied to hepatic resection / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the impact of preoperative three-dimensional visualization and virtual liver surgery planning on hepatic resection.</p><p><b>METHODS</b>All relevant structures (livers, portal vein, hepatic veins, and tumors) were extracted from multislice CT scans of 142 cases treated from May 2007 to May 2009. By the liver surgery planning system software Liv 1.0, reconstruction and image analysis of the relevant structures was performed and virtual resections of liver were carried out. Data were correlated to intraoperative findings.</p><p><b>RESULTS</b>(1) Three-dimensional visualization revealed the spatial relationship of tumors to the intrahepatic vascular system, thus giving impressions how the neoplasms were situated. Virtual tumor resections corresponded to the intraoperative findings. (2) With the planning, an intended resection could be performed virtually and optimal identification of resection margins could be achieved. The ischemia and congestion territory within the remaining liver parenchyma could be calculated. Simulation resections could avoid liver parenchyma over resection and maintain a sufficient amount of liver tissue to sustain hepatic function. Virtual simulations of tumor resection were used successfully to plan of surgical procedures in the hepatic tumors. Hepatectomy was performed in 29 cases after virtual tumor resections but seemed impossible with conventional CT scan. Resection plans of 92 cases were optimized after virtual resections. (3) The mean liver volume of patients with primary hepatocellular carcinoma measured by the software and the real resected was (477 +/- 223) ml and (451 +/- 209) ml respectively. Comparison by means of linear regression analysis between volume measurement on the software and the real resected showed a nearly ideal correlation coefficient (R = 0.922, P < 0.01). The mean error was 6.1%.</p><p><b>CONCLUSIONS</b>The three-dimensional tumor visualization and virtual simulation of tumor resections of the software Liv 1.0 provide an important reference for a valuable planning of complex hepatic resections. It is not only benefit to improve the predictability and security of hepatectomy but also helpful to improve the success rate of complex hepatic resections.</p>

The role of extracellular signal-regulated kinase/mitogen-activated protein kinase pathway in multidrug resistance of hepatocellular carcinoma / 中华外科杂志

<p><b>OBJECTIVE</b>To elucidate intracellular signal pathway in formation of multidrug resistance (MDR) of hepatocellular carcinoma (HCC) induced by its microenvironment, and to explore the potential role of extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) pathway in this process.</p><p><b>METHODS</b>Activity of ERK/MAPK was examined by Western blot technique through comparing the ratio of phosphorylation of ERK/MAPK to total ERK/MAPK protein in HepG2 cells exposed to hypoxia, low glucose or transfected by plasmid pcDNA3/HBX. After being treated by the specific ERK/MAPK pathway inhibitor U0126, Western blot technique was used to analyze the alterations of the expression of P-gp, MRP1, LRP and HIF-1alpha at protein level. RT-PCR was used to analyze the alterations of the expression of HIF-1alpha mRNA. Cellular location of HIF-1alpha protein was determined by immunocytochemistry after being treated by U0126.</p><p><b>RESULTS</b>The activations of ERK/MAPK determined by the ratio of phosphorylated ERK/MAPK to the total ERK/MAPK were increased in varying degrees in HepG2 cells respectively exposed to different microenvironment. After being treated by U0126 for 12 h, the expressions of mdr1, MRP1, LRP genes and protein in those cells were decreased to some extent. However, the gene expression of HIF-1alpha was not influenced and only its protein was decreased. HIF-1alpha protein was reversely translocated into cytoplasm from nucleus after being treated by U0126.</p><p><b>CONCLUSIONS</b>ERK/MAPK pathway is involved in the course of the formation of MDR of HCC induced by microenvironment.</p>

Hypoxia-inducible factor-1 alpha dependent expression and significance of the related multidrug resistance genes induced by hypoxia in human hepatocarcinoma cell / 中华外科杂志

<p><b>OBJECTIVE</b>To explore the mechanism of multidrug resistance of hepatocellular carcinoma induced by hypoxia and the potential role of hypoxia-inducible factor-1 alpha (HIF-1 alpha) and multidrug resistance related genes.</p><p><b>METHODS</b>Human hepatocarcinoma cell lines HepG2 cells were exposed to hypoxia and were transfected by plasmid HIF-1 alpha/PCDNA3, respectively. The expressions of multidrug resistance gene (mdr1), multidrug resistance protein (MRP1), and lung resistance protein (LRP) gene at the mRNA and the protein levels in the above two groups were respectively analyzed by real-time fluorescent quantitative PCR and Western-blot technique.</p><p><b>RESULTS</b>In the hypoxia group, the expressions of mdr1, MRP1 and LRP were stepped up correlating to the degree of hypoxia, especially the prominent increase in the expression of MRP1. Furthermore, they were synchronous with the changes of the expression of HIF-1 alpha. Also the increased expression of mdr1, MRP1, and LRP gene was observed in transfected HepG2 cells by plasmid HIF-1 alpha/PCDNA3.</p><p><b>CONCLUSIONS</b>Resistance of hepatocellular carcinoma to chemotherapeutics could be induced by hypoxia. HIF-1 alpha may be critical to the upregulation of the expression of the related multidrug resistance genes induced by hypoxia. HIF-1 alpha and these related multidrug resistance genes could be potential molecular targets for reversing multidrug resistance of hepatocellular carcinoma.</p>