[The role of extracellular signal-regulated kinase/mitogen-activated protein kinase pathway in multidrug resistance of hepatocellular carcinoma].
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
ERK/MAPK pathway is involved in the course of the formation of MDR of HCC induced by microenvironment.
Zhu
Hong
H
Department of Preclinical Medicine, Medical School of Soochow University, Suzhou 215006, China. zhuhong_jasmine@suda.edu.cn
Chen
Xiao-Ping
XP
Luo
Shun-Feng
SF
Guan
Jian
J
Zhang
Wan-Guang
WG
Zhang
Bi-Xiang
BX
Mao
Cai-Ping
CP
D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D048049:Extracellular Signal-Regulated MAP Kinases; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D020928:Mitogen-Activated Protein Kinases; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012333:RNA, Messenger