Effect of cellular ATP depletion on topoisomerase II poisons. Abrogation Of cleavable-complex formation by etoposide but not by amsacrine.
Topoisomerase (topo) II poisons have been categorized into ATP-independent and -dependent drugs based on in vitro studies. We investigated drug-induced topoII-DNA complexes in intact cells almost completely depleted of ATP. Virtually no DNA single-strand breaks (SSBs), as measured by alkaline elution, were detected in energy-depleted cells treated with the topoII poisons etoposide, teniposide, daunorubicin, doxorubicin, mitoxantrone, or clerocidin. This inhibition was reversible; subsequent incubation with glucose restored the level of DNA SSBs. The effect of ATP depletion was specific for topoII, because topoI-mediated cleavable complexes induced by camptothecin were unaffected by ATP depletion. Furthermore, etoposide-induced DNA-protein complexes and DNA double-strand breaks, as measured by filter elution techniques, and topoIIalpha and -beta trapping, as measured by a band depletion assay, were completely inhibited by energy depletion. Differences in drug transport could not explain the effect of ATP depletion. The topoII poison amsacrine (m-AMSA) was unique with respect to ATP dependence. In ATP-depleted cells, m-AMSA-induced DNA SSBs, DNA double-strand breaks, DNA-protein complexes, topoIIalpha and -beta trapping were only modestly reduced. The accumulation of m-AMSA was reduced in ATP-depleted cells, which indicates that drug transport could contribute to the modest decrease in m-AMSA-induced cleavable complexes. In conclusion, drug-induced topoII-DNA complexes were completely antagonized in ATP-depleted cells, except in the case of m-AMSA. One possible interpretation is that m-AMSA mainly produces prestrand passage DNA lesions, whereas the other topoII poisons tested exclusively stabilize poststrand passage DNA lesions in intact cells.
Sorensen
M
M
Laboratory of Experimental Medical Oncology, The Finsen Center, Rigshospitalet, Copenhagen, Denmark. msorensen@dadlnet.dk
Sehested
M
M
Jensen
P B
PB
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000677:Amsacrine / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D018736:DNA Adducts / Q000187:drug effects; D004249:DNA Damage; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology*; D006801:Humans; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D018736:DNA Adducts; D004268:DNA-Binding Proteins; D059005:Topoisomerase II Inhibitors; D000677:Amsacrine; D005047:Etoposide; D000255:Adenosine Triphosphate; D004250:DNA Topoisomerases, Type II