Synergism between etoposide and 17-AAG in leukemia cells: critical roles for Hsp90, FLT3, topoisomerase II, Chk1, and Rad51.

Abstract

PURPOSE:

DNA-damaging agents, such as etoposide, while clinically useful in leukemia therapy, are limited by DNA repair pathways that are not well understood. 17-(Allylamino)-17-demethoxygeldanamycin (17-AAG), an inhibitor of the molecular chaperone heat shock protein 90 (Hsp90), inhibits growth and induces apoptosis in FLT3(+) leukemia cells. In this study, we evaluated the effects of etoposide and 17-AAG in leukemia cells and the roles of Hsp90, FMS-like tyrosine kinase 3 (FLT3), checkpoint kinase 1 (Chk1), Rad51, and topoisomerase II in this inhibition.

EXPERIMENTAL DESIGN:

The single and combined effects of 17-AAG and etoposide and the mechanism of these effects were evaluated. FLT3 and the DNA repair-related proteins, Chk1 and Rad51, were studied in small interfering RNA (siRNA)-induced cell growth inhibition experiments in human leukemia cells with wild-type or mutated FLT3.

RESULTS:

We found that etoposide and the Hsp90/FLT3 inhibitor 17-AAG, had synergistic inhibitory effects on FLT3(+) MLL-fusion gene leukemia cells. Cells with an internal tandem duplication (ITD) FLT3 (Molm13 and MV4;11) were more sensitive to etoposide/17-AAG than leukemias with wild-type FLT3 (HPB-Null and RS4;11). A critical role for FLT3 was shown in experiments with FLT3 ligand and siRNA targeted to FLT3. An important role for topoisomerase II and the DNA repair-related proteins, Chk1 and Rad51, in the synergistic effects was suggested from the results.

CONCLUSIONS:

The repair of potentially lethal DNA damage by etoposide in leukemia cells is dependent on intact and functioning FLT3 especially leukemias with ITD-FLT3. These data suggest a rational therapeutic strategy for FLT3(+) leukemias that combines etoposide or other DNA-damaging agents with Hsp90/FLT3 inhibitors such as 17-AAG.

• Authors: Qing Yao, Brenda Weigel, John Kersey
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 13 Issue 5 Pg. 1591-600 (Mar 01 2007) ISSN: 1078-0432 [Print] United States
• PMID: 17332306 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Benzoquinones
• HSP90 Heat-Shock Proteins
• Lactams, Macrocyclic
• RNA, Small Interfering
• tanespimycin
• Etoposide
• Protein Kinases
• FLT3 protein, human
• fms-Like Tyrosine Kinase 3
• CHEK1 protein, human
• Checkpoint Kinase 1
• Rad51 Recombinase
• DNA Topoisomerases, Type II
• DNA Repair Enzymes

Topics

• Antineoplastic Agents (pharmacology)
• Benzoquinones (pharmacology)
• Blotting, Western
• Cell Line, Tumor
• Checkpoint Kinase 1
• DNA Repair Enzymes (drug effects)
• DNA Topoisomerases, Type II (drug effects, metabolism)
• Drug Synergism
• Etoposide (pharmacology)
• HSP90 Heat-Shock Proteins (drug effects, metabolism)
• Humans
• Lactams, Macrocyclic (pharmacology)
• Leukemia (drug therapy)
• Protein Kinases (drug effects, metabolism)
• RNA, Small Interfering
• Rad51 Recombinase (drug effects, metabolism)
• fms-Like Tyrosine Kinase 3 (drug effects, metabolism)