Anthracycline drugs are potent anti-tumor agents. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a death ligand with promising anti-cancer effects. However, some tumor types develop resistance to TRAIL. We examined the effect of aclarubicin (ACR), an anthracycline, in combination with TRAIL. The combination of TRAIL and ACR synergistically induced apoptosis in human acute lymphoblastic leukemia Jurkat cells and human lung cancer A549 cells. In contrast, another anthracycline, doxorubicin (DOX), only slightly sensitized Jurkat cells and A549 cells to TRAIL-induced apoptosis, with weaker enhancement of death receptor 5 (DR5) expression than ACR. The RNase protection assay, real time RT-PCR and western blot demonstrated that ACR upregulated the expression of a TRAIL receptor, DR5. Caspase inhibitors and dominant negative DR5 efficiently reduced the apoptotic response to the treatment with ACR and TRAIL, indicating that the combined effect depends on caspase activities and the interaction between TRAIL and its receptor. ACR but not DOX increased the activity of the DR5 gene promoter in Jurkat cells carrying a mutation in the p53 gene, suggesting that ACR upregulates DR5 expression through p53-independent transcription. These results suggest the combination of TRAIL and ACR to be a promising treatment for malignant tumors.
© 2011 Japanese Cancer Association.