Rational Drug Design: An Information Driven Approach to the Design of an Anthracycline Analog

Over the past fifty years anthracyclines have been used to treat a wide variety of cancers. Combination therapies with anthracyclines have the potential to greatly increase treatment success. Despite the great potential of anthracyclines in the treatment of cancer, their use has been limited due to the risk of chronic cardiotoxicity. The reduction of anthracyclines to an alcohol metabolite has been linked to the development of cardiotoxic side effects. One of the principal enzymes responsible for catalyzing the formation of the anthracycline alcohol metabolite is human carbonyl reductase 1(HCBR). Controlling the reduction of anthracyclines by HCBR may offer a means to reduce the risk of cardiotoxicity during treatment. The structure activity relationships responsible for the recognition and binding of the anthracycline substrates were investigated. Molecular modeling studies implicated Met 234 as a possible determinant of anthracycline specificity for HCBR. In order to test this, site directed mutagenesis was used to convert the methionine to a cysteine in a histidine expression system. The histidine tagged HCBR was found to have reduced enzyme activity and coenzyme binding compared to native enzyme. Further, the cysteine 234 mutant enzyme was found to be inactive, although it still appeared to possess coenzyme and anthracycline binding capability. It is clear that the addition of the histidine tag has impaired enzyme function and that such a modification may mask any effects introduced by mutating Met 234 to a cysteine (NIH-INBRE Grant# P20RR16454)