Inhibition of translesion DNA synthesis as a novel therapeutic strategy to treat brain cancer

Temozolomide is a DNA alkylating agent used to treat brain tumors but resistance to this drug is common. In this study, we provide evidence that efficacious responses to this drug can be heightened significantly by co-administration of an artificial nucleoside (5-NIdR) that efficiently and selectively inhibits the replication of DNA lesions generated by temozolomide. Conversion of this compound to the corresponding nucleoside triphosphate 5-NITP in vivo creates a potent inhibitor of several human DNA polymerases that can replicate damaged DNA. Accordingly, 5-NIdR synergized with temozolomide to increase apoptosis of tumor cells. In a murine xenograft model of glioblastoma, whereas temozolomide only delayed tumor growth its co-administration with 5-NIdR caused complete tumor regression. Exploratory toxicology investigations showed that high doses of 5-NIdR did not produce the side effects commonly seen with conventional nucleoside analogs. Collectively, our results offer a preclinical pharmacological proof of concept for the coordinate inhibition of translesion DNA synthesis as a strategy to improve chemotherapeutic responses in aggressive brain tumors.

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