Increased glutathione and mitogen-activated protein kinase phosphorylation are involved in the induction of doxorubicin resistance in hepatocellular carcinoma cells

Aim: The human hepatocellular carcinoma (HCC) cell line HepG2 can easily acquire resistance to doxorubicin. However, the mechanism of action is unclear. Methods: In the present study, we used confocal microscopy, flow cytometry and other methods to reveal the mechanisms by which HepG2 cells acquire doxorubicin resistance. Results: Our results showed that R-HepG2 cells, a doxorubicin-resistant sub-line of HepG2, exhibited decreased intracellular accumulation of doxorubicin and increased expression of P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 when compared with HepG2 cells. R-HepG2 cells also harbored higher levels of glutathione and increased expression of glutathione peroxidase. Furthermore, we demonstrated that the phosphorylation of mitogen-activated protein kinases (p38 and c-jun-N-terminal kinases), IkB and CREB were increased in R-HepG2 cells. Specific p38 inhibitor SB203580 decreased P-gp expression. The multi-kinase inhibitor sorafenib tosylate also significantly suppressed the phosphorylation of these proteins and inhibited the expression of P-gp. Conclusion: These findings reveal that the drug resistance could be acquired through mitogen-activated protein kinase-dependent upregulation of P-gp. This mechanism protects R-HepG2 cells from the anticancer action of doxorubicin.