Dihydroartemisinin treatment of multiple myeloma cells causes activation of c-Jun leading to cell apoptosis

The aim of the present study was to investigate the effect of dihydroartemisinin (DHA) on a multiple myeloma cell line. An MTT assay, flow cytometry and reverse transcription-polymerase chain reaction (RT-PCR) were used for the analysis of cell viability, cell cycle distribution and c-Jun N-terminal kinase (JNK) expression, respectively. Treatment of U266 cells using DHA caused a significant (P<0.05) decrease in cell viability compared with the control cells. An increase in the concentration of DHA from 1 to 100 mu mol/l reduced cell viability from 87 to 35% compared with 100% in the control cultures at 48 h. A significant (P<0.05) increase was observed in the sub-G(0)/G(1), phase population of the U266 cells with an increase in DHA concentration from 1 to 100 mu mol/l. Treatment with 1, 3, 10, 30 and 100 mu mol/l concentrations of DHA increased the sub-G(0)/G(1), phase cell population to 3.13, 8.25, 24.91, 31.47 and 38.54%, respectively. RT-PCR analysis of DHA-treated or-untreated U266 cells after 48 h demonstrated a significant (P<0.01) increase in caspase-3 expression. Treatment of the cells for 48 h with DHA led to a significant increase in c-Jun expression. DHA treatment at 1, 3, 10, 30 and 100 mu mol/l concentrations caused an increase in the level of c-Jun by 0.174 +/- 0.001, 0.254 +/- 0.002, 0.387 +/- 0.001, 0.502 +/- 0.003 and 0.679 +/- 0.005, respectively, compared with 0.982 +/- 0.001 in the control cells. The addition of SP600125 to the cells incubated with DHA resulted in a significant decrease in the caspase-3 and c-Jun expression levels compared with those cells incubated with DHA alone. These findings confirm that treatment with DHA increased caspase-3 and c-Jun expression in the U266 cells through activation of the JNK signaling pathway. Thus, DHA inhibited proliferation of multiple myeloma cells by interfering with the JNK signaling pathway.