Background Accumu1αting 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 re1...Background Accumu1αting 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 re1αted to environmental factors that are common with tumor growth of hepatocellu1αr carcinoma. The aim of this study was to explore the molecu1αr mechanisms by which multidrug resistance of hepatocellu1αr carcinoma is induced by the microenvironment. In particu1αr, the regu1αtion of nuclear transcription factor （hypoxia-inducible factor-1α, HIF-1α） activation in the process of multidrug resistance formation was investigated. Methods HepG2 cells were exposed to different microenvironmental conditions respectively, such as hypoxia, stimu1αtion of glucose deprivation and transfection of p1αsmid PcDNA3/HBx. In the HepG2 cells, the expression of the re1αted MDR proteins, HIF-1α protein expression and localization, activity of extracellu1αr signal-regu1αted 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 re1αted 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. Results The above three microenvironment factors increase the expression of the re1αted 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 decreased. Inhibition of ERK/MAPK significantly reduced HIF-1α, whereas HIF-1α mRNA levels were not affected. expression of MDR1, MRP1, and LRP was to some extent activated HIF-1α protein and the nuclear translocation of Conclusions The microenvironmental factors could induce MDR of HepG2 cells by the activity of HIF-1α. The activity of HIF-1α is regu1αted by the ERK/MAPK pathway at the phosphory1αtion level. As an important nuclear transcription factor, HIF-1α controls the transcription of MDR-re1αted genes and the synthesis of their corresponding proteins by ERK/MAPK signal pathway in HepG2 cells.展开更多
基金This work was supported by grants from Suzhou City Research Foundation for Applied Basic Research （No. YJS0930）, Natural Science Foundation of the Jiangsu Higher Education Institutions of China （No. 10KJB320020）, National Natural Science Foundation of China （No. 81000944） and Research Foundation for ＂Reserved Academic Leader＂ from the Second Affiliated Hospital of Soochow University.Acknowledgments： We greatly appreciate Dr. ZHAO Lian-rui, from Thomas Jefferson University, Philadelphia, PA, USA, for his a kind gift of the pcDNA3fHBx plasmid. We also thank Dr. J. Tian for technical assistance for this work.
文摘Background Accumu1αting 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 re1αted to environmental factors that are common with tumor growth of hepatocellu1αr carcinoma. The aim of this study was to explore the molecu1αr mechanisms by which multidrug resistance of hepatocellu1αr carcinoma is induced by the microenvironment. In particu1αr, the regu1αtion of nuclear transcription factor （hypoxia-inducible factor-1α, HIF-1α） activation in the process of multidrug resistance formation was investigated. Methods HepG2 cells were exposed to different microenvironmental conditions respectively, such as hypoxia, stimu1αtion of glucose deprivation and transfection of p1αsmid PcDNA3/HBx. In the HepG2 cells, the expression of the re1αted MDR proteins, HIF-1α protein expression and localization, activity of extracellu1αr signal-regu1αted 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 re1αted 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. Results The above three microenvironment factors increase the expression of the re1αted 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 decreased. Inhibition of ERK/MAPK significantly reduced HIF-1α, whereas HIF-1α mRNA levels were not affected. expression of MDR1, MRP1, and LRP was to some extent activated HIF-1α protein and the nuclear translocation of Conclusions The microenvironmental factors could induce MDR of HepG2 cells by the activity of HIF-1α. The activity of HIF-1α is regu1αted by the ERK/MAPK pathway at the phosphory1αtion level. As an important nuclear transcription factor, HIF-1α controls the transcription of MDR-re1αted genes and the synthesis of their corresponding proteins by ERK/MAPK signal pathway in HepG2 cells.
