A novel mechanism of cell killing by anti-topoisomerase II bisdioxopiperazines.

Abstract

Bisdioxopiperazines are a unique class of topoisomerase II inhibitors that lock topoisomerase II at a point in the enzyme reaction cycle where the enzyme forms a closed clamp around DNA. We examined cell killing by ICRF-187 and ICRF-193 in yeast cells expressing human topoisomerase II alpha (htop-IIalpha). Expression of htop-IIalpha in yeast cells sensitizes them to both ICRF-187 and ICRF-193, compared with cells expressing yeast topoisomerase II. ICRF-193 is still able to exert growth inhibition in the presence of genes encoding both ICRF-193-resistant and ICRF-193-sensitive htop-IIalpha enzymes, indicating that sensitivity to bisdioxopiperazines is dominant. Killing by ICRF-193 occurs more rapidly, than the killing in yeast cells due to a temperature-sensitive yeast topoisomerase II incubated at the non-permissive temperature. These results are reminiscent of a top-II poison such as etoposide. However, the killing caused by ICRF-193 and ICRF-187 is not enhanced by mutations in the RAD52 pathway. The levels of drug-induced DNA cleavage observed with htop-IIalpha in vitro is insufficient to explain the sensitivity induced by this enzyme in yeast cells. Finally, arrest of cells in G(1) does not protect cells from ICRF-193 lethality, a result inconsistent with killing mechanisms due to catalytic inhibition of top-II or stabilization of a cleavable complex. We suggest that the observed pattern of cell killing is most consistent with a poisoning of htop-II by ICRF-193 by a novel mechanism. The accumulation of closed clamp conformations of htop-II induced by ICRF-193 that are trapped on DNA might interfere with transcription, or other DNA metabolic processes, resulting in cell death.

• Authors: L H Jensen, K C Nitiss, A Rose, J Dong, J Zhou, T Hu, N Osheroff, P B Jensen, M Sehested, J L Nitiss
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 275 Issue 3 Pg. 2137-46 (Jan 21 2000) ISSN: 0021-9258 [Print] United States
• PMID: 10636919 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antineoplastic Agents
• Diketopiperazines
• Enzyme Inhibitors
• Piperazines
• Topoisomerase II Inhibitors
• 4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione
• Razoxane
• DNA Topoisomerases, Type II

Topics

• Alleles
• Antineoplastic Agents (pharmacology)
• Cell Cycle (drug effects)
• DNA Topoisomerases, Type II (genetics, metabolism)
• Diketopiperazines
• Dose-Response Relationship, Drug
• Drug Resistance, Microbial
• Enzyme Inhibitors (pharmacology)
• Genes, Dominant
• Humans
• Microbial Sensitivity Tests
• Mutagenesis
• Piperazines (pharmacology)
• Protein Conformation
• Razoxane (pharmacology)
• Saccharomyces cerevisiae (drug effects)
• Time Factors
• Topoisomerase II Inhibitors
• Ultracentrifugation