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.