Differentiation induction of human promyelocytic leukemia cells by 10-hydroxycamptothecin, a DNA topoisomerase I inhibitor.
The cytotoxic and differentiating effects of 10-hydroxycamptothecin (HCPT) in the human promyelocytic leukemia cell line HL-60 were examined. By trypan blue dye exclusion, a 24-h exposure of the cells to 0.1 microM of the drug was found to be cytotoxic. Exposure of the cells to lower concentrations (0.001-0.01 microM) for 3 days reduced cell proliferation and induced cell differentiation. As determined by Wright-Giemsa staining, approximately 25% of promyelocytic cells became metamyelocytes, banded and segmented neutrophils. Electron microscopy demonstrated alterations in the ultrastructure of HCPT-induced HL-60 cells that included the formation of lobulated nuclei and the accumulation of large vesicles and small myelin bodies as well as glycogen-like particles in the cell periphery. Qualitatively similar results were obtained in a subline of HL-60 that is resistant to 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA); however, the rate and extent of induced nitroblue tetrazolium-positive cells by HCPT and several other agents were greater in the resistant cell line. Under conditions that induced cell differentiation, HCPT sharply inhibited [3H]thymidine incorporation into DNA and increased the rate of protein synthesis without an effect on the rate of RNA synthesis. The measurement of DNA topoisomerase I activity in nuclear extracts from both HCPT- and DMSO-treated cells demonstrated that the enzyme was decreased in mature cells compared to nondifferentiated controls. The data suggest that progressive reduction of DNA topoisomerase I activity may be associated with cell differentiation, but whether HCPT-induced differentiation is mediated by inhibition of the enzyme is inconclusive.
Ling
Y H
YH
Department of Experimental Pediatrics, University of Texas, M.D. Anderson Cancer Center, Houston 77030.
Tseng
M T
MT
Nelson
J A
JA
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D004264:DNA Topoisomerases, Type I / Q000502:physiology; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology*; D009363:Neoplasm Proteins / Q000096:biosynthesis; D012334:RNA, Neoplasm / Q000096:biosynthesis; D013997:Time Factors; D059004:Topoisomerase I Inhibitors; D014407:Tumor Cells, Cultured
D000972:Antineoplastic Agents, Phytogenic; D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D012334:RNA, Neoplasm; D059004:Topoisomerase I Inhibitors; C028098:10-hydroxycamptothecin; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin