Inhibition of p34cdc2 dephosphorylation in DNA damage- and topoisomerase II inactivation-induced G2 arrests in HL-60 cells.
Doxorubicin induces DNA breakage by stabilizing a cleavable topoisomerase II-DNA complex. In contrast, topoisomerase II catalytic inhibitor ICRF-193 and uncoupling inhibitor aclarubicin interfere with the cleavable complex formation. We analysed combination effects of these drugs using two-dimensional flow cytometry of DNA content and the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labelling assay. Both ICRF-193 and aclarubicin attenuated the cytotoxic effect of doxorubicin on HL-60 cells (85% and 46% maximum reduction, respectively), which suggested that doxorubicin exerts its cytotoxic effect at least partially through the topoisomerase II-dependent DNA cleavage. Doxorubicin and ICRF-193 both induced G2 arrest in HL-60 cells, by which they may have reduced the cytotoxic effect of vincristine. Indeed, although ICRF-193 inhibited doxorubicin-induced apoptosis, ICRF-193 and doxorubicin cooperated in arresting HL-60 cells at G2 phase. These results indicated that G2 arrest was caused not only by DNA damage but also through a DNA damage-free, topoisomerase II inactivation-induced pathway. Western blot analysis showed that both types of G2 arrest were mediated by the inhibition of p34cdc2 dephosphorylation.
Sugimoto
K
K
Department of Haematology, Juntendo University School of Medicine, Tokyo, Japan.
Sasaki
M
M
Tamayose
K
K
Oshimi
K
K
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004317:Doxorubicin / Q000494:pharmacology; D016195:G2 Phase / Q000187:drug effects; D018922:HL-60 Cells / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D018613:Microscopy, Confocal; D010766:Phosphorylation; D014750:Vincristine / Q000494:pharmacology
D000970:Antineoplastic Agents; D014750:Vincristine; D004317:Doxorubicin; D016203:CDC2 Protein Kinase; D004250:DNA Topoisomerases, Type II