Molecular modeling of new camptothecin analogues to circumvent ABCG2-mediated drug resistance in cancer.

Hiroshi Nakagawa, Hikaru Saito, Yoji Ikegami, Sachiko Aida-Hyugaji, Seigo Sawada, Toshihisa Ishikawa

Department of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8501, Japan.

Cancer letters 2006 Mar 8

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Irinotecan (CPT-11) is a widely used potent antitumor drug that inhibits mammalian DNA topoisomerase I (Topo I). However, overexpression of ABCG2 (BCRP/MXR/ABCP) reportedly confers cancer cells resistance to SN-38, the active form of CPT-11. To circumvent the ABCG2-associated drug resistance, the structure-activity-relationship (SAR) of 14 new camptothecin (CPT) analogues has been studied with respect to the substrate specificity of ABCG2. While the lactone E ring is a prerequisite for anticancer activity, modifications of the A or B rings do not significantly affect Topo I inhibition. Based on the substrate specificity of ABCG2, it is strongly suggested that CPT analogues with a hydroxyl group at position 10 or 11 of the A ring are recognized by ABCG2 and are thereby effectively extruded from cancer cells. To develop a platform for the molecular modeling to circumvent anticancer drug resistance, we have carried out quantum chemical calculations and neural network SAR analysis. Electrostatic potential iso-surfaces generated by ab initio MO calculations using restricted Hartree-Fock method have revealed that negative potential localized at positions 10 or 11 in the A ring is important for recognition by ABCG2.

Citation

Hiroshi Nakagawa, Hikaru Saito, Yoji Ikegami, Sachiko Aida-Hyugaji, Seigo Sawada, Toshihisa Ishikawa. Molecular modeling of new camptothecin analogues to circumvent ABCG2-mediated drug resistance in cancer. Cancer letters. 2006 Mar 8;234(1):81-9