In vitro and in vivo inhibition of tumor cell viability by combined dihydroartemisinin and doxorubicin treatment, and the underlying mechanism

The natural extract artemisinin and its derivatives have good anticancer activity. The present study aimed to investigate the in vitro inhibitory effects of combined dihydroartemisinin (DHA) and doxorubicin (DOX) treatment on a variety of tumor cell lines (HeLa, OVCAR-3, MCF-7, PC-3 and A549), as well as the underlying mechanisms. In addition, the in vivo effects of DHA and DOX were evaluated using a mouse HeLa tumor model. The HeLa, OVCAR-3, MCF-7, PC-3 and A549 cells were treated with a combination of DHA and DOX, and the effect on cell viability was detected by Cell Counting kit-8. The cells were observed under a fluorescence microscope after staining with Hoechst 33258 dye to observe morphological changes in the nuclei in order to determine whether the cells in the treatment group exhibited apoptosis. Apoptosis of the cells was further detected by flow cytometry, and statistical analysis was performed. The specific inhibitors of caspase-3, −8 and −9 were used to determine the intrinsic and extrinsic pathways of cell apoptosis. The cervical cancer HeLa cells treated with the combination of DHA and DOX showed up to a 91.5% decrease in viability, which was higher than that of the same cells treated with DHA or DOX alone at the same concentration, respectively (P<0.01). The optimal concentrations of the drugs used in combination were DHA at 10 µg/ml and DOX at 10 µg/ml. DHA + DOX also had a significant inhibitory effect on the ovarian cancer (OVCAR-3), breast cancer (MCF-7), lung cancer (A549) and prostate cancer (PC-3) cells. The images observed under fluorescence microscope after Hoechst 33258 staining showed marked pyknosis in the cells treated with DHA + DOX, similar to that when treated with DHA or DOX alone, which is typical in apoptosis. As determined by flow cytometry, the apoptotic rate of the cells treated with DHA + DOX at optimal concentrations was up to 90%, which was significantly higher than that of the cells treated with DHA or DOX alone at the same concentration. Caspase-9 and −3 inhibitors significantly increased the viability of the cells treated with DHA + DOX. At 6 days post-intratumoral injection of DHA + DOX, the tumor volume was markedly reduced. In vivo toxicity results revealed that the combination of the drugs had basically no effect on the body weight of the mice and had no significant toxicity on the liver, spleen, kidneys and heart of the animals. Overall, the combination of DHA and DOX markedly inhibited the viability of the HeLa, OVCAR-3, MCF-7, PC-3 and A549 cells, and acted on the HeLa cells through the intrinsic apoptotic pathway mediated by caspase-9 and caspase-3. DHA + DOX also had a significant treatment effect in vivo. This study provides a novel idea for the development of a clinical medication against several types of cancer.