Activity of a novel camptothecin analogue, homocamptothecin, in camptothecin-resistant cell lines with topoisomerase I alterations.
Homocamptothecin (hCPT), which differs from camptothecin (CPT) by the presence of an additional methylene group in the E-ring, was evaluated in CPT-resistant cell lines. Topoisomerase I (top1)-deficient leukemia P388/CPT45 cells were highly resistant to hCPT, which demonstrates that top1 is the primary target of hCPT. Three CPT-resistant cell lines with top1 point mutations (Chinese hamster lung fibroblast DC3F/C10, human prostate carcinoma DU-145/RC1, and human leukemia CEM/C2) and their top1 enzymes were cross-resistant to hCPT. The antiproliferative activity of hCPT was greater than that of CPT in both parental and CPT-resistant cell lines, particularly in the prostate cell lines. The top1 cleavage complexes formed in the presence of hCPT appear to be more stable than those induced by CPT. Together, these data indicate that hCPT is a specific top1 inhibitor, which shares a common binding site with CPT in the topl-DNA cleavage complexes. Because of its potency, hCPT might overcome resistance to CPT in some cancer cells.
Urasaki
Y
Y
Laboratory of Molecular Pharmacology, Division of Baisic Sciences, National Cancer Institute, NIH, Bethesda, Maryland 20892-4255, USA.
Takebayashi
Y
Y
Pommier
Y
Y
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006224:Cricetinae; D004264:DNA Topoisomerases, Type I / Q000235:genetics*; D004273:DNA, Neoplasm / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004795:Enzyme Stability / Q000187:drug effects; D006801:Humans; D020128:Inhibitory Concentration 50; D007941:Leukemia P388 / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D008297:Male; D051379:Mice; D017354:Point Mutation; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics; D059004:Topoisomerase I Inhibitors; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D059004:Topoisomerase I Inhibitors; C120029:homocamptothecin; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin