Abstract
Agents that target topoisomerase I are widely utilized to treat human cancer. Previous studies have indicated that both the ataxia telangiectasia mutated (ATM)/checkpoint kinase (Chk) 2 and ATM- and Rad 3-related (ATR)/Chk1 checkpoint pathways are activated after treatment with these agents. The relative contributions of these two pathways to survival of cells after treatment with topoisomerase I poisons are currently unknown. To address this issue, we assessed the roles of ATR, Chk1, ATM, and Chk2 in cells treated with the topoisomerase I poisons camptothecin and 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan. Colony forming assays demonstrated that down-regulation of ATR or Chk1 sensitized cells to SN-38 and camptothecin. In contrast, ATM and Chk2 had minimal effect of sensitivity to SN-38 or camptothecin. Additional experiments demonstrated that the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin, which down-regulates Chk1, also sensitized a variety of human carcinoma cell lines to SN-38. Collectively, these results show that the ATR/Chk1 pathway plays a predominant role in the response to topoisomerase I inhibitors in carcinoma cells and identify a potential approach for enhancing the efficacy of these drugs.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Antineoplastic Agents, Phytogenic / metabolism
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Antineoplastic Agents, Phytogenic / therapeutic use
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Ataxia Telangiectasia Mutated Proteins
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Camptothecin / analogs & derivatives
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Camptothecin / metabolism
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Camptothecin / therapeutic use
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism
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Cell Line
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Checkpoint Kinase 1
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Checkpoint Kinase 2
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DNA Topoisomerases, Type I / metabolism*
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Gene Deletion
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Genes, cdc
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HSP90 Heat-Shock Proteins / antagonists & inhibitors
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HSP90 Heat-Shock Proteins / metabolism
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Humans
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Neoplasms / drug therapy
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Neoplasms / metabolism*
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Protein Kinases / genetics
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Protein Kinases / metabolism*
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Topoisomerase I Inhibitors*
Substances
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Antineoplastic Agents, Phytogenic
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Cell Cycle Proteins
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HSP90 Heat-Shock Proteins
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RNA, Small Interfering
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Topoisomerase I Inhibitors
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Protein Kinases
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Checkpoint Kinase 2
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ATR protein, human
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Ataxia Telangiectasia Mutated Proteins
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CHEK1 protein, human
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CHEK2 protein, human
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Checkpoint Kinase 1
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Protein Serine-Threonine Kinases
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DNA Topoisomerases, Type I
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Camptothecin