Differences in Transport Characteristics and Cytotoxicity of Epirubicin and Doxorubicin in HepG2 and A549 Cells

Abstract

Epirubicin (EPI), an epimer of doxorubicin (DOX), and DOX are anthracycline agents with broad-spectrum antitumor activity. The aim of the present study was to elucidate the transport characteristics of EPI and DOX in human hepatocellular carcinoma HepG2 cells and human non-small cell lung cancer A549 cells, and to examine the relationship of intracellular drug accumulation with their cytotoxic effects. Intracellular concentrations of EPI and DOX were measured using high-performance liquid chromatography (HPLC). Expression level of targeted genes was analyzed by real-time quantitative PCR. Cell viability was evaluated using the MTT assay. Similar to DOX, EPI was taken up into HepG2 and A549 cells by organic cation transporter 6 and passive diffusion; however, the efficiency of saturable and non-saturable uptake of EPI was greater than that of DOX in both cell types. EPI served as a substrate of P-glycoprotein and multidrug associated protein (MRP) 1 and MRP2 similarly to DOX, but the efflux efficiency of each transporter was markedly different between EPI and DOX. The intracellular accumulation of EPI was significantly greater than that of DOX in all cells, and the accumulated level reflected the cytotoxic effects of these drugs. However, the intracellular drug amount did not correspond to the degree of cytotoxicity when compared between HepG2 and A549 cells, which can be explained by the higher expression of Bcl-xl in A549 cells. This study suggested that the transport characteristics are markedly different between EPI and DOX in HepG2 and A549 cells, and that intracellular accumulation is the predominant factor affecting the cytotoxicity of EPI and DOX in individual cells.