Rational Inhibitors of DNA Base Excision Repair Enzymes: New Tools for Elucidating the Role of BER in Cancer Chemotherapy. Addendum

摘要

The aim of this research program was to investigate the role of the uracil base excision repair (UBER) pathway in the mechanism of action of the antineoplastic agent 5-fluorouracil (5-FU) through the discovery and development of inhibitors against UBER enzymes. Over the course of this funding period, we have developed novel, potent oligonucleotide and small molecule inhibitors of the first enzyme in the UBER pathway, uracil DNA glycosylase (UDG) as outlined in Tasks 1 and 2 of the approved Statement of Work. Using these inhibitors, we were able to greatly expand our understanding of how UDG recognizes and interacts with normal and uracil-containing DNA. However, the limited cell penetrance and/or potencies of these compounds hindered their use in dissecting the interactions between UDG and 5-FU in cellulo (Task 3 of the approved Statement of Work). Instead, a yeast genetics approach was used, where the cytotoxicity and potency of 5-FU was determined against a panel of UBER mutants. Consistent with the model that UBER potentiates the cytotoxicity of 5- FU through futile DNA repair, a UDG knockout yeast strain is resistant to 5-FU, while a yeast strain that lacks the ability to process abasic sites (a UBER repair intermediate) is hypersensitive to 5-FU. These results suggest that inhibitors of abasic site processing enzymes in the UBER pathway could be useful agents in the potentation of 5-FU antineoplastic activity.