An artificial nucleoside that simultaneously detects and combats drug resistance to doxorubicin

OBJECTIVES Doxorubicin is a DNA-damaging agent used to treat hematological cancers. Unfortunately, drug resistance can occur by defective DNA repair activity coupled with the ability of DNA polymerases to misreplicate unrepaired DNA lesions. This study demonstrates that the efficacy of doxorubicin can be improved by using an artificial nucleoside to efficiently and selectively inhibit this activity. METHODS In vitro studies using acute lymphoblastic leukemia cell lines define the mechanism of cell death caused by combining an artificial nucleoside with doxorubicin. RESULTS Flow cytometry experiments demonstrate that combining an artificial nucleoside with doxorubicin potentiates the cell killing effects of the drug by increasing apoptosis. The potentiation effect correlates with expression of TdT, a specialized DNA polymerase overexpressed in acute lymphoblastic leukemia. Cell cycle experiments demonstrate that this combination blocks cells at S-phase prior to inducing apoptosis. Finally, the unique chemical composition of the nucleoside analog was used to visualize the replication of damaged DNA in TdT-positive cells. This represents a potential diagnostic tool to easily identify doxorubicin-resistant cancer cells. CONCLUSION Studies demonstrate that a novel artificial nucleoside improves the therapeutic efficacy of doxorubicin, thereby reducing the risk of potential side effects caused by the DNA-damaging agent.