title: Molecular and cellular pharmacology of the novel noncamptothecin topoisomerase I inhibitor Genz-644282.
abstract: Camptothecin derivatives are powerful anticancer drugs because of their ability to trap topoisomerase I (Top1)-DNA cleavage complexes. However, they exhibit clinical limitations due to the instability of their α-hydroxylactone six-membered E-ring structure. In addition, they exhibit bone marrow and intestinal toxicity, especially in adults, and are drug efflux substrates. Here, we report a novel Top1 inhibitor, Genz-644282. We show that Genz-644282 and its metabolites induce Top1 cleavage at similar, as well as unique genomic positions, compared with camptothecin. The compound also induces protein-linked DNA breaks and Top1-DNA cleavage complexes that persist longer after compound removal than camptothecin. Concentration-dependent and persistent γH2AX formation was readily observed in cells treated with Genz-644282, and was present in greater than 50% of the cell population following 24 hours compound exposure. The compound shows partial cross-resistance in cell lines resistant to camptothecin. These cell lines include the human prostate DU145RC0.1 and the leukemic CEM/C2 cells. Limited cross-resistance to Genz-644282 was also found in the Top1 knockdown colon cancer (HCT116) and breast cancer (MCF7) cell lines and in human adenocarcinoma cells (KB31/KBV1) that overexpress (P-glycoprotein, ABCB1), a member of the ATP-binding cassette family of cell surface transport proteins known to confer MDR. Together, our results provide the first molecular and cellular characterization of Genz-644282 and its clinically relevant metabolites.
authors.affiliation: Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
authors.forename: Dhriti
authors.initials: D
authors.lastname: Sooryakumar
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Dexheimer
authors.forename: Beverly A
authors.initials: BA
authors.lastname: Teicher
authors.forename: Yves
authors.initials: Y
authors.lastname: Pommier
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001483:Base Sequence; D002166:Camptothecin / Q000494:pharmacology; D045744:Cell Line, Tumor; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D045325:HCT116 Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D009287:Naphthyridines / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology; D059004:Topoisomerase I Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; C560916:Genz-644282; C468783:H2AX protein, human; D006657:Histones; D009287:Naphthyridines; D059004:Topoisomerase I Inhibitors; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin