JNK1, JNK2, and JNK3 are involved in P-glycoprotein-mediated multidrug resistance of hepatocellular carcinoma cells.

Background: Multidrug resistance (MDR) is extremely common in hepatocellular carcinoma (HCC) and is a major problem in cancer eradication by limiting the efficacy of chemotherapy. Modulation of c-Jun NH2-terminal kinase (JNK) activation could be a new method to reverse MDR. However, the relationship between JNK activity and MDR in HCC cells is unknown. This study aimed to explore the relationship between MDR and JNK in HCC cell lines with different degrees of MDR.

Methods: A MDR human HCC cell line, SMMC-7721/ADM, was developed by exposing parental cells to gradually increasing concentrations of adriamycin. The MTT assay was used to determine drug sensitivity. Flow cytometry was used to analyze the cell cycle distribution and to measure the expression levels of P-glycoprotein (P-gp) and MDR-related protein (MRP)-1 in these cells. JNK1, JNK2 and JNK3 mRNA expression levels were quantified by real-time PCR. Expression and phosphorylation of JNK1, JNK2, and JNK3 were analyzed by Western blotting.

Results: The MDR of SMMC-7721/ADM cells resistant to 0.05 mg/L adriamycin was mainly attributed to the overexpression of P-gp but not MRP1. In addition, these cells had a significant increase in percentage in the S phase, accompanied by a decrease in percentage in the G0/G1 phase, which is likely associated with a reduced ability for cell proliferation and MDR generation. We found that JNK1, JNK2, and JNK3 activities were negatively correlated with the degree of MDR in HCC cells.

Conclusion: This study suggests that JNK1, JNK2, and JNK3 activities are negatively correlated with the degree of MDR in HCC cells.