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David Ross - One of the best experts on this subject based on the ideXlab platform.
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Abstract 1788: 19-Substituted benzoquinone Ansamycins. Hsp90 inhibitors with decreased off-target toxicity
Cancer Research, 2014Co-Authors: Chuan-hsin Chang, David Siegel, Derek A. Drechsel, Russell R. A. Kitson, Donald S. Backos, Cynthia Ju, Christopher J. Moody, David RossAbstract:Benzoquinone Ansamycin (BQA) Hsp90 inhibitors such as 17-DMAG and 17-AAG have off-target toxicities in clinical trials including hepatotoxicity. Mechanisms underlying the toxicity of quinones are a function of their ability to redox cycle and/or arylate cellular nucleophiles at the unsubstituted 19-position of the molecule. Therefore, we designed 19-substituted BQAs to prevent glutathione conjugation and non-specific interactions with protein thiols as an approach to reduce the hepatotoxicity and minimize off-target effects of the BQA class of Hsp90 inhibitors. In this study, the results showed that 19-substituted BQAs did not react with glutathione at the 19-position, while marked reactivity was observed using parent BQAs. Importantly, while parent 17-DMAG induced cell death in primary and cultured mouse hepatocytes, 19-phenyl and 19-methyl 17-DMAG showed reduced toxicity, validating the overall approach. There was no significant difference between the redox cycling ability of either 19-phenyl or 19-methyl 17-DMAG with their parental BQAs in both mouse and human liver microsomes. Accordingly, this suggests that arylation reactions at the unsubstituted 19-position are predominantly responsible for hepatotoxicity. 19-substituted17-DMAG inhibited purified Hsp90 ATPase activity in an NQO1-dependent manner that demonstrated increased inhibitory efficacy of the hydroquinone Ansamycin relative to its parent quinone. In human breast cancer cells, 19-phenyl BQAs induced growth inhibition in an NQO1-dependent manner with molecular signatures of Hsp90 inhibition, including decreases in client proteins and compensatory induction of Hsp70. These data indicate that 19-substituted BQAs may be useful Hsp90 inhibitors with decreased off target toxicity (Supported by NCI grant CA51210) Citation Format: Chuan-Hsin Chang, Derek A. Drechsel, Russell R.A. Kitson, David Siegel, Qiang You, Donald S. Backos, Cynthia Ju, Christopher J. Moody, David Ross. 19-Substituted benzoquinone Ansamycins. Hsp90 inhibitors with decreased off-target toxicity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1788. doi:10.1158/1538-7445.AM2014-1788
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19 substituted benzoquinone Ansamycin heat shock protein 90 inhibitors biological activity and decreased off target toxicity
Molecular Pharmacology, 2014Co-Authors: Chuan-hsin Chang, David Siegel, Derek A. Drechsel, Russell R. A. Kitson, Donald S. Backos, Christopher J. Moody, Changqing Ju, David RossAbstract:The benzoquinone Ansamycins (BQAs) are a valuable class of antitumor agents that serve as inhibitors of heat shock protein (Hsp)-90. However, clinical use of BQAs has resulted in off-target toxicities, including concerns of hepatotoxicity. Mechanisms underlying the toxicity of quinones include their ability to redox cycle and/or arylate cellular nucleophiles. We have therefore designed 19-substituted BQAs to prevent glutathione conjugation and nonspecific interactions with protein thiols to minimize off-target effects and reduce hepatotoxicity. 19-Phenyl– and 19-methyl–substituted versions of geldanamycin and its derivatives, 17-allylamino-17-demethoxygeldanamycin and 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG), did not react with glutathione, whereas marked reactivity was observed using parent BQAs. Importantly, although 17-DMAG induced cell death in primary and cultured mouse hepatocytes, 19-phenyl and 19-methyl DMAG showed reduced toxicity, validating the overall approach. Furthermore, our data suggest that arylation reactions, rather than redox cycling, are a major mechanism contributing to BQA hepatotoxicity. 19-Phenyl BQAs inhibited purified Hsp90 in a NAD(P)H:quinone oxidoreductase 1 (NQO1)–dependent manner, demonstrating increased efficacy of the hydroquinone Ansamycin relative to its parent quinone. Molecular modeling supported increased stability of the hydroquinone form of 19-phenyl-DMAG in the active site of human Hsp90. In human breast cancer cells, 19-phenyl BQAs induced growth inhibition also dependent upon metabolism via NQO1 with decreased expression of client proteins and compensatory induction of Hsp70. These data demonstrate that 19-substituted BQAs are unreactive with thiols, display reduced hepatotoxicity, and retain Hsp90 and growth-inhibitory activity in human breast cancer cells, although with diminished potency relative to parent BQAs.
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Abstract 2769: The development of 19-substituted benzoquinone Ansamycins as potential anticancer drugs
Cancer Research, 2012Co-Authors: Chuan-hsin Chang, David Siegel, Russell R. A. Kitson, Christopher J. Moody, David RossAbstract:Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Benzoquinone Ansamycins (BQA's) were the first class of Hsp90 inhibitors developed but the use of the prototype agent geldanamycin was limited by hepatotoxicity. One major mechanism of toxicity of the BQA class is manifested via the electrophilic properties of the quinone and alkylation of cellular nucleophiles at the 19-position. We developed novel 19-substituted BQA's in the geldanamycin (GA), 17-AAG and 17-DMAG series as a means to prevent arylation of cellular nucleophiles. 19-substituted BQA's inhibited recombinant Hsp90 and did not react with thiols at the 19-position while marked thiol reactivity could be detected using their parent quinones. We examined the effects of different substitution patterns at the 19-position on the ability of BQAs to inhibit Hsp90 and induce growth inhibitory effects in breast cancer cell lines. We found that both 19-phenyl and 19-methyl BQA's in the 17-AAG, 17-DMAG and GA series were effective inhibitors of purified Hsp90 as demonstrated using an ATPase assay particularly in the presence of NQO1 to generate the hydroquinone Ansamycin. Only 19-phenyl substituted BQAs were effective growth inhibitory agents in breast cancer cell lines using an MTT assay while 19-methyl substituted BQAs in the GA, 17-AAG and 17-DMAG series demonstrated only modest growth inhibition. The growth inhibitory effects of 19-phenyl BQAs were potentiated in cells containing high NQO1. Notably, 19-phenyl DMAG had similar growth inhibitory and apoptotic effects as its parent quinone, DMAG. These data demonstrate that the 19-phenyl BQAs had marked growth inhibitory, apoptotic, and client protein expression effect in breast cancer cells compared to 19-methyl BQAs (Supported by CA 51210). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2769. doi:1538-7445.AM2012-2769
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abstract b102 19 substituted benzoquinone Ansamycins decreasing the toxicity of the benzoquinone Ansamycin class of hsp90 inhibitors
Molecular Cancer Therapeutics, 2011Co-Authors: Chuan-hsin Chang, Philip Reigan, David Siegel, Russell R. A. Kitson, Christopher J. Moody, David RossAbstract:Benzoquinone Ansamycins (BQAs) were the first class of Hsp90 inhibitors developed but members of this class, particularly geldanamycin, demonstrated hepatic toxicity. One major mechanism of toxicity of the BQA class is manifested via the electrophilic properties of the quinone and arylation of cellular nucleophiles at the 19-position of the Ansamycin ring. Using selective halogenation and palladium-catalyzed coupling, we have synthesized a number of novel 19-substituted BQAs in the geldanamycin, 17-AAG and 17-DMAG series as a means to prevent arylation of cellular nucleophiles and have validated this approach using model thiols including N-acetylcysteine and glutathione. 19-Substituted BQAs did not react with thiols at the 19-position while marked reactivity could be detected using their parent quinones. 19-Substituted BQAs were tested for their ability to inhibit recombinant yeast Hsp90 and 19-substitution did not block the capacity of these novel molecules to inhibit the ATPase activity of the Hsp90 chaperone. This result was confirmed by molecular modeling of 19-substituted derivatives in the active site of human Hsp90 demonstrating that 19-substitution did not block entry of the molecule into the active site. The addition of NAD(P)H:quinone oxidoreductase 1 (NQO1) potentiated inhibition of recombinant yeast Hsp90 by 19-substituted BQAs confirming our previous data demonstrating increased inhibitory efficacy of the hydroquinone Ansamycin relative to its parent quinone. Cellular effects of 19-substituted BQAs were examined in MDA468 breast cancer cells and the isogenic MDA468/NQ16 cell line which over-expresses NQO1. Growth inhibitory effects were observed using 19-substituted BQAs and were potentiated by the presence of NQO1 in the MDA468/NQ16 line. Hsp90 inhibition in MDA468 and MDA468/NQ16 cells was confirmed using decreases in the Hsp90 client protein Raf1 and a compensatory increase in Hsp70 as biomarkers. In summary, these data demonstrate that 19-substituted BQAs do not react with thiols at the 19-position but retain their Hsp90 inhibitory capacity using purified enzyme and in cells suggesting that they should undergo further translational evaluation as therapeutic candidates (Supported by CA51210 and the Parkinsons Disease Society UK). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B102.
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A Mechanistic and Structural Analysis of the Inhibition of the 90-kDa Heat Shock Protein by the Benzoquinone and Hydroquinone Ansamycins
Molecular Pharmacology, 2011Co-Authors: Philip Reigan, David Siegel, David RossAbstract:The benzoquinone Ansamycins inhibit the ATPase activity of the 90-kDa heat shock protein (Hsp90), disrupting the function of numerous client proteins involved in oncogenesis. In this study, we examine the role of NAD(P)H:quinone oxidoreductase 1 (NQO1) in the metabolism of trans- and cis-amide isomers of the benzoquinone Ansamycins and their mechanism of Hsp90 inhibition. Inhibition of purified human Hsp90 by a series of benzoquinone Ansamycins was examined in the presence and absence of NQO1, and their relative rate of NQO1-mediated reduction was determined. Computational-based molecular docking simulations indicated that the trans- but not the cis-amide isomers of the benzoquinone Ansamycins could be accommodated by the NQO1 active site, and the ranking order of binding energies correlated with the relative reduction rate using purified human NQO1. The trans-cis isomerization of the benzoquinone Ansamycins in Hsp90 inhibition has been disputed in recent reports. Previous computational studies have used the closed or cocrystallized Hsp90 structures in an attempt to explore this isomerization step; however, we have successfully docked both the trans- and cis-amide isomers of the benzoquinone Ansamycins into the open Hsp90 structure. The results of these studies indicate that both trans- and cis-amide isomers of the hydroquinone Ansamycins exhibited increased binding affinity for Hsp90 relative to their parent quinones. Our data support a mechanism in which trans- rather than cis-amide forms of benzoquinone Ansamycins are metabolized by NQO1 to hydroquinone Ansamycins and that Hsp90-mediated trans-cis isomerization via tautomerization plays an important role in subsequent Hsp90 inhibition.
Chunhua Lu - One of the best experts on this subject based on the ideXlab platform.
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targeted discovery of pentaketide Ansamycin aminoAnsamycinsa g
Organic Letters, 2019Co-Authors: Zishen Wang, Chunhua Lu, Yaoyao Li, Haoxin Wang, Yuemao ShenAbstract:Ansamycins are a class of macrolactams with diverse bioactivities, characterized by the unique 3-amino-5-hydroxybenzoic acid moiety. In this study, the Ansamycin gene cluster aas in Streptomyces sp. S35 was activated by the constitutive coexpression of two pathway-specific regulator genes aas1 and aas10, and seven novel pentaketide Ansamycin aminoAnsamycins A–G (1–7) were identified. Compound 4 with better antiproliferative activity indicated that the anthranilate analogues are probably promising building blocks for the production of unnatural Ansamycins with improved activity.
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Targeted Discovery of Pentaketide Ansamycin AminoAnsamycinsA–G
Organic Letters, 2019Co-Authors: Zishen Wang, Chunhua Lu, Yaoyao Li, Haoxin Wang, Yuemao ShenAbstract:Ansamycins are a class of macrolactams with diverse bioactivities, characterized by the unique 3-amino-5-hydroxybenzoic acid moiety. In this study, the Ansamycin gene cluster aas in Streptomyces sp. S35 was activated by the constitutive coexpression of two pathway-specific regulator genes aas1 and aas10, and seven novel pentaketide Ansamycin aminoAnsamycins A–G (1–7) were identified. Compound 4 with better antiproliferative activity indicated that the anthranilate analogues are probably promising building blocks for the production of unnatural Ansamycins with improved activity.
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pentaketide Ansamycin microAnsamycins a i from micromonospora sp reveal diverse post pks modifications
Organic Letters, 2018Co-Authors: Jianxiong Wang, Haoxin Wang, Wen Li, Chunhua LuAbstract:Overexpression of the pathway-specific positive regulator gene mas13 activated the cryptic gene cluster mas, resulting in the isolation of nine novel pentaketide Ansamycins, namely, microAnsamycins A–I (1–9). These results not only revealed a biosynthetic gene cluster of pentaketide Ansamycins for the first time but also presented an unprecedented scenario of diverse post-PKS modifications in Ansamycin biosynthesis.
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Pentaketide Ansamycin MicroAnsamycins A–I from Micromonospora sp. Reveal Diverse Post-PKS Modifications
Organic Letters, 2018Co-Authors: Jianxiong Wang, Haoxin Wang, Wen Li, Chunhua LuAbstract:Overexpression of the pathway-specific positive regulator gene mas13 activated the cryptic gene cluster mas, resulting in the isolation of nine novel pentaketide Ansamycins, namely, microAnsamycins A–I (1–9). These results not only revealed a biosynthetic gene cluster of pentaketide Ansamycins for the first time but also presented an unprecedented scenario of diverse post-PKS modifications in Ansamycin biosynthesis.
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Abscisic acid-type sesquiterpenes and Ansamycins from Amycolatopsis alba DSM 44262
Journal of Asian Natural Products Research, 2017Co-Authors: Xiao-mei Li, Xiao-man Li, Chunhua LuAbstract:AbstractTwo new abscisic acid-type sesquiterpenes (1, 2), and one new Ansamycin (3), together with four known Ansamycins, namely ansacarbamitocins 4–7, were isolated from the fermentation extract of Amycolatopsis alba DSM 44262. The structures of the new compounds were elucidated to be (E)-3-methyl-5-(2,6,6-trimethyl-3-oxocyclohex-1-enyl)pent-2-enoic acid (1) and (E)-3-methyl-5-(2,6,6-trimethyl-4-oxocyclohex-2-enyl)pent-2-enoic acid (2), and 9-O-methylansacarbamitocin A1 (3), on the basis of comprehensive analysis of spectroscopic data, respectively. The antimicrobial activities were also evaluated for all seven compounds.
David Siegel - One of the best experts on this subject based on the ideXlab platform.
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Abstract 1788: 19-Substituted benzoquinone Ansamycins. Hsp90 inhibitors with decreased off-target toxicity
Cancer Research, 2014Co-Authors: Chuan-hsin Chang, David Siegel, Derek A. Drechsel, Russell R. A. Kitson, Donald S. Backos, Cynthia Ju, Christopher J. Moody, David RossAbstract:Benzoquinone Ansamycin (BQA) Hsp90 inhibitors such as 17-DMAG and 17-AAG have off-target toxicities in clinical trials including hepatotoxicity. Mechanisms underlying the toxicity of quinones are a function of their ability to redox cycle and/or arylate cellular nucleophiles at the unsubstituted 19-position of the molecule. Therefore, we designed 19-substituted BQAs to prevent glutathione conjugation and non-specific interactions with protein thiols as an approach to reduce the hepatotoxicity and minimize off-target effects of the BQA class of Hsp90 inhibitors. In this study, the results showed that 19-substituted BQAs did not react with glutathione at the 19-position, while marked reactivity was observed using parent BQAs. Importantly, while parent 17-DMAG induced cell death in primary and cultured mouse hepatocytes, 19-phenyl and 19-methyl 17-DMAG showed reduced toxicity, validating the overall approach. There was no significant difference between the redox cycling ability of either 19-phenyl or 19-methyl 17-DMAG with their parental BQAs in both mouse and human liver microsomes. Accordingly, this suggests that arylation reactions at the unsubstituted 19-position are predominantly responsible for hepatotoxicity. 19-substituted17-DMAG inhibited purified Hsp90 ATPase activity in an NQO1-dependent manner that demonstrated increased inhibitory efficacy of the hydroquinone Ansamycin relative to its parent quinone. In human breast cancer cells, 19-phenyl BQAs induced growth inhibition in an NQO1-dependent manner with molecular signatures of Hsp90 inhibition, including decreases in client proteins and compensatory induction of Hsp70. These data indicate that 19-substituted BQAs may be useful Hsp90 inhibitors with decreased off target toxicity (Supported by NCI grant CA51210) Citation Format: Chuan-Hsin Chang, Derek A. Drechsel, Russell R.A. Kitson, David Siegel, Qiang You, Donald S. Backos, Cynthia Ju, Christopher J. Moody, David Ross. 19-Substituted benzoquinone Ansamycins. Hsp90 inhibitors with decreased off-target toxicity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1788. doi:10.1158/1538-7445.AM2014-1788
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19 substituted benzoquinone Ansamycin heat shock protein 90 inhibitors biological activity and decreased off target toxicity
Molecular Pharmacology, 2014Co-Authors: Chuan-hsin Chang, David Siegel, Derek A. Drechsel, Russell R. A. Kitson, Donald S. Backos, Christopher J. Moody, Changqing Ju, David RossAbstract:The benzoquinone Ansamycins (BQAs) are a valuable class of antitumor agents that serve as inhibitors of heat shock protein (Hsp)-90. However, clinical use of BQAs has resulted in off-target toxicities, including concerns of hepatotoxicity. Mechanisms underlying the toxicity of quinones include their ability to redox cycle and/or arylate cellular nucleophiles. We have therefore designed 19-substituted BQAs to prevent glutathione conjugation and nonspecific interactions with protein thiols to minimize off-target effects and reduce hepatotoxicity. 19-Phenyl– and 19-methyl–substituted versions of geldanamycin and its derivatives, 17-allylamino-17-demethoxygeldanamycin and 17-(dimethylaminoethylamino)-17-demethoxygeldanamycin (17-DMAG), did not react with glutathione, whereas marked reactivity was observed using parent BQAs. Importantly, although 17-DMAG induced cell death in primary and cultured mouse hepatocytes, 19-phenyl and 19-methyl DMAG showed reduced toxicity, validating the overall approach. Furthermore, our data suggest that arylation reactions, rather than redox cycling, are a major mechanism contributing to BQA hepatotoxicity. 19-Phenyl BQAs inhibited purified Hsp90 in a NAD(P)H:quinone oxidoreductase 1 (NQO1)–dependent manner, demonstrating increased efficacy of the hydroquinone Ansamycin relative to its parent quinone. Molecular modeling supported increased stability of the hydroquinone form of 19-phenyl-DMAG in the active site of human Hsp90. In human breast cancer cells, 19-phenyl BQAs induced growth inhibition also dependent upon metabolism via NQO1 with decreased expression of client proteins and compensatory induction of Hsp70. These data demonstrate that 19-substituted BQAs are unreactive with thiols, display reduced hepatotoxicity, and retain Hsp90 and growth-inhibitory activity in human breast cancer cells, although with diminished potency relative to parent BQAs.
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Abstract 2769: The development of 19-substituted benzoquinone Ansamycins as potential anticancer drugs
Cancer Research, 2012Co-Authors: Chuan-hsin Chang, David Siegel, Russell R. A. Kitson, Christopher J. Moody, David RossAbstract:Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Benzoquinone Ansamycins (BQA's) were the first class of Hsp90 inhibitors developed but the use of the prototype agent geldanamycin was limited by hepatotoxicity. One major mechanism of toxicity of the BQA class is manifested via the electrophilic properties of the quinone and alkylation of cellular nucleophiles at the 19-position. We developed novel 19-substituted BQA's in the geldanamycin (GA), 17-AAG and 17-DMAG series as a means to prevent arylation of cellular nucleophiles. 19-substituted BQA's inhibited recombinant Hsp90 and did not react with thiols at the 19-position while marked thiol reactivity could be detected using their parent quinones. We examined the effects of different substitution patterns at the 19-position on the ability of BQAs to inhibit Hsp90 and induce growth inhibitory effects in breast cancer cell lines. We found that both 19-phenyl and 19-methyl BQA's in the 17-AAG, 17-DMAG and GA series were effective inhibitors of purified Hsp90 as demonstrated using an ATPase assay particularly in the presence of NQO1 to generate the hydroquinone Ansamycin. Only 19-phenyl substituted BQAs were effective growth inhibitory agents in breast cancer cell lines using an MTT assay while 19-methyl substituted BQAs in the GA, 17-AAG and 17-DMAG series demonstrated only modest growth inhibition. The growth inhibitory effects of 19-phenyl BQAs were potentiated in cells containing high NQO1. Notably, 19-phenyl DMAG had similar growth inhibitory and apoptotic effects as its parent quinone, DMAG. These data demonstrate that the 19-phenyl BQAs had marked growth inhibitory, apoptotic, and client protein expression effect in breast cancer cells compared to 19-methyl BQAs (Supported by CA 51210). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2769. doi:1538-7445.AM2012-2769
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abstract b102 19 substituted benzoquinone Ansamycins decreasing the toxicity of the benzoquinone Ansamycin class of hsp90 inhibitors
Molecular Cancer Therapeutics, 2011Co-Authors: Chuan-hsin Chang, Philip Reigan, David Siegel, Russell R. A. Kitson, Christopher J. Moody, David RossAbstract:Benzoquinone Ansamycins (BQAs) were the first class of Hsp90 inhibitors developed but members of this class, particularly geldanamycin, demonstrated hepatic toxicity. One major mechanism of toxicity of the BQA class is manifested via the electrophilic properties of the quinone and arylation of cellular nucleophiles at the 19-position of the Ansamycin ring. Using selective halogenation and palladium-catalyzed coupling, we have synthesized a number of novel 19-substituted BQAs in the geldanamycin, 17-AAG and 17-DMAG series as a means to prevent arylation of cellular nucleophiles and have validated this approach using model thiols including N-acetylcysteine and glutathione. 19-Substituted BQAs did not react with thiols at the 19-position while marked reactivity could be detected using their parent quinones. 19-Substituted BQAs were tested for their ability to inhibit recombinant yeast Hsp90 and 19-substitution did not block the capacity of these novel molecules to inhibit the ATPase activity of the Hsp90 chaperone. This result was confirmed by molecular modeling of 19-substituted derivatives in the active site of human Hsp90 demonstrating that 19-substitution did not block entry of the molecule into the active site. The addition of NAD(P)H:quinone oxidoreductase 1 (NQO1) potentiated inhibition of recombinant yeast Hsp90 by 19-substituted BQAs confirming our previous data demonstrating increased inhibitory efficacy of the hydroquinone Ansamycin relative to its parent quinone. Cellular effects of 19-substituted BQAs were examined in MDA468 breast cancer cells and the isogenic MDA468/NQ16 cell line which over-expresses NQO1. Growth inhibitory effects were observed using 19-substituted BQAs and were potentiated by the presence of NQO1 in the MDA468/NQ16 line. Hsp90 inhibition in MDA468 and MDA468/NQ16 cells was confirmed using decreases in the Hsp90 client protein Raf1 and a compensatory increase in Hsp70 as biomarkers. In summary, these data demonstrate that 19-substituted BQAs do not react with thiols at the 19-position but retain their Hsp90 inhibitory capacity using purified enzyme and in cells suggesting that they should undergo further translational evaluation as therapeutic candidates (Supported by CA51210 and the Parkinsons Disease Society UK). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B102.
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A Mechanistic and Structural Analysis of the Inhibition of the 90-kDa Heat Shock Protein by the Benzoquinone and Hydroquinone Ansamycins
Molecular Pharmacology, 2011Co-Authors: Philip Reigan, David Siegel, David RossAbstract:The benzoquinone Ansamycins inhibit the ATPase activity of the 90-kDa heat shock protein (Hsp90), disrupting the function of numerous client proteins involved in oncogenesis. In this study, we examine the role of NAD(P)H:quinone oxidoreductase 1 (NQO1) in the metabolism of trans- and cis-amide isomers of the benzoquinone Ansamycins and their mechanism of Hsp90 inhibition. Inhibition of purified human Hsp90 by a series of benzoquinone Ansamycins was examined in the presence and absence of NQO1, and their relative rate of NQO1-mediated reduction was determined. Computational-based molecular docking simulations indicated that the trans- but not the cis-amide isomers of the benzoquinone Ansamycins could be accommodated by the NQO1 active site, and the ranking order of binding energies correlated with the relative reduction rate using purified human NQO1. The trans-cis isomerization of the benzoquinone Ansamycins in Hsp90 inhibition has been disputed in recent reports. Previous computational studies have used the closed or cocrystallized Hsp90 structures in an attempt to explore this isomerization step; however, we have successfully docked both the trans- and cis-amide isomers of the benzoquinone Ansamycins into the open Hsp90 structure. The results of these studies indicate that both trans- and cis-amide isomers of the hydroquinone Ansamycins exhibited increased binding affinity for Hsp90 relative to their parent quinones. Our data support a mechanism in which trans- rather than cis-amide forms of benzoquinone Ansamycins are metabolized by NQO1 to hydroquinone Ansamycins and that Hsp90-mediated trans-cis isomerization via tautomerization plays an important role in subsequent Hsp90 inhibition.
Philip Reigan - One of the best experts on this subject based on the ideXlab platform.
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abstract b102 19 substituted benzoquinone Ansamycins decreasing the toxicity of the benzoquinone Ansamycin class of hsp90 inhibitors
Molecular Cancer Therapeutics, 2011Co-Authors: Chuan-hsin Chang, Philip Reigan, David Siegel, Russell R. A. Kitson, Christopher J. Moody, David RossAbstract:Benzoquinone Ansamycins (BQAs) were the first class of Hsp90 inhibitors developed but members of this class, particularly geldanamycin, demonstrated hepatic toxicity. One major mechanism of toxicity of the BQA class is manifested via the electrophilic properties of the quinone and arylation of cellular nucleophiles at the 19-position of the Ansamycin ring. Using selective halogenation and palladium-catalyzed coupling, we have synthesized a number of novel 19-substituted BQAs in the geldanamycin, 17-AAG and 17-DMAG series as a means to prevent arylation of cellular nucleophiles and have validated this approach using model thiols including N-acetylcysteine and glutathione. 19-Substituted BQAs did not react with thiols at the 19-position while marked reactivity could be detected using their parent quinones. 19-Substituted BQAs were tested for their ability to inhibit recombinant yeast Hsp90 and 19-substitution did not block the capacity of these novel molecules to inhibit the ATPase activity of the Hsp90 chaperone. This result was confirmed by molecular modeling of 19-substituted derivatives in the active site of human Hsp90 demonstrating that 19-substitution did not block entry of the molecule into the active site. The addition of NAD(P)H:quinone oxidoreductase 1 (NQO1) potentiated inhibition of recombinant yeast Hsp90 by 19-substituted BQAs confirming our previous data demonstrating increased inhibitory efficacy of the hydroquinone Ansamycin relative to its parent quinone. Cellular effects of 19-substituted BQAs were examined in MDA468 breast cancer cells and the isogenic MDA468/NQ16 cell line which over-expresses NQO1. Growth inhibitory effects were observed using 19-substituted BQAs and were potentiated by the presence of NQO1 in the MDA468/NQ16 line. Hsp90 inhibition in MDA468 and MDA468/NQ16 cells was confirmed using decreases in the Hsp90 client protein Raf1 and a compensatory increase in Hsp70 as biomarkers. In summary, these data demonstrate that 19-substituted BQAs do not react with thiols at the 19-position but retain their Hsp90 inhibitory capacity using purified enzyme and in cells suggesting that they should undergo further translational evaluation as therapeutic candidates (Supported by CA51210 and the Parkinsons Disease Society UK). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B102.
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A Mechanistic and Structural Analysis of the Inhibition of the 90-kDa Heat Shock Protein by the Benzoquinone and Hydroquinone Ansamycins
Molecular Pharmacology, 2011Co-Authors: Philip Reigan, David Siegel, David RossAbstract:The benzoquinone Ansamycins inhibit the ATPase activity of the 90-kDa heat shock protein (Hsp90), disrupting the function of numerous client proteins involved in oncogenesis. In this study, we examine the role of NAD(P)H:quinone oxidoreductase 1 (NQO1) in the metabolism of trans- and cis-amide isomers of the benzoquinone Ansamycins and their mechanism of Hsp90 inhibition. Inhibition of purified human Hsp90 by a series of benzoquinone Ansamycins was examined in the presence and absence of NQO1, and their relative rate of NQO1-mediated reduction was determined. Computational-based molecular docking simulations indicated that the trans- but not the cis-amide isomers of the benzoquinone Ansamycins could be accommodated by the NQO1 active site, and the ranking order of binding energies correlated with the relative reduction rate using purified human NQO1. The trans-cis isomerization of the benzoquinone Ansamycins in Hsp90 inhibition has been disputed in recent reports. Previous computational studies have used the closed or cocrystallized Hsp90 structures in an attempt to explore this isomerization step; however, we have successfully docked both the trans- and cis-amide isomers of the benzoquinone Ansamycins into the open Hsp90 structure. The results of these studies indicate that both trans- and cis-amide isomers of the hydroquinone Ansamycins exhibited increased binding affinity for Hsp90 relative to their parent quinones. Our data support a mechanism in which trans- rather than cis-amide forms of benzoquinone Ansamycins are metabolized by NQO1 to hydroquinone Ansamycins and that Hsp90-mediated trans-cis isomerization via tautomerization plays an important role in subsequent Hsp90 inhibition.
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enzymatic reduction and glutathione conjugation of benzoquinone Ansamycin heat shock protein 90 inhibitors relevance for toxicity and mechanism of action
Drug Metabolism and Disposition, 2008Co-Authors: Philip Reigan, David Siegel, David RossAbstract:Two-electron reduction of benzoquinone Ansamycin (BA) heat shock protein (Hsp) 90 inhibitors by NAD(P)H:quinone oxidoreductase 1 (NQO1) to hydroquinone Ansamycins (BAH2s) leads to greater Hsp90 inhibitory activity. BAs can also be metabolized by one-electron reductases and can interact with glutathione, reactions that have been associated with toxicity. Using a series of BAs, we investigated the stability of the BAH2s generated by NQO1, the ability of BAs to be metabolized by one-electron reductases, and their conjugation with glutathione. The BAs used were geldanamycin (GM), 17-(allylamino)-17-demethoxygeldanamycin (17AAG), 17-demethoxy-17-[[2-(dimethyl amino)ethyl]amino]-geldanamycin (17DMAG), 17-(amino)-17-demethoxygeldanamycin (17AG), and 17-demethoxy-17-[[2-(pyrrolidin-1-yl)ethyl]amino]-geldanamycin (17AEP-GA). The relative stabilities of BAH2s at pH 7.4 were GM hydroquinone > 17AAG hydroquinone > 17DMAG hydroquinone > 17AG hydroquinone and 17AEP-GA hydroquinone. Using human and mouse liver microsomes and either NADPH or NADH as cofactors, 17AAG had the lowest rate of one-electron reduction, whereas GM had the highest rate. 17DMAG demonstrated the greatest rate of redox cycling catalyzed by purified human cytochrome P450 reductase, whereas 17AAG again had the slowest rate. GM formed a glutathione adduct most readily followed by 17DMAG. The formation of glutathione adducts of 17AAG and 17AG were relatively slow in comparison. These data demonstrate that GM, the most hepatotoxic BAs in the series had a greater propensity to undergo redox cycling reactions catalyzed by hepatic one-electron reductases and markedly greater reactivity with thiols when compared with the least hepatotoxic analog 17AAG. Minimizing the propensity of BA derivatives to undergo one-electron reduction and glutathione conjugation while maximizing their two-electron reduction to stable Hsp90 inhibitory hydroquinones may be a useful strategy for optimizing the therapeutic index of BAs.
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The Bioreduction of a Series of Benzoquinone Ansamycins by NAD(P)H:Quinone Oxidoreductase 1 to More Potent Heat Shock Protein 90 Inhibitors, the Hydroquinone Ansamycins
Molecular Pharmacology, 2006Co-Authors: Philip Reigan, David Siegel, Joseph A. Zirrolli, Daniel L. Gustafson, David RossAbstract:We have previously evaluated the role of NAD(P)H:quinone oxidoreductase 1 (NQO1) in the bioreductive metabolism of 17-(allylamino)-demethoxygeldanamycin (17AAG) to the corresponding hydroquinone, a more potent 90-kDa heat shock protein (Hsp90) inhibitor. Here, we report an extensive study with a series of benzoquinone Ansamycins, which includes gel-danamycin, 17-(amino)-17-demethoxygeldanamycin, and 17-demethoxy-17-[[2-(dimethylamino)ethyl]amino]-geldanamycin. The reduction of these benzoquinone Ansamycins by recombinant human NQO1 to the corresponding hydroquinone Ansamycins was monitored by high-performance liquid chromatography (HPLC) and confirmed by liquid chromatography/mass spectrometry. Inhibition of purified yeast Hsp90 ATPase activity was augmented in the presence of NQO1 and abrogated by 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl-]indole-4,7-dione (ES936), a mechanism-based inhibitor of NQO1, showing that the hydroquinone Ansamycins were more potent Hsp90 inhibitors than their parent quinones. An isogenic pair of human breast cancer cell lines, MDA468 and MDA468/NQ16, differing in expression of NQO1, was used, and HPLC analysis showed that hydroquinone Ansamycins were formed by the MDA468/NQ16 cells, which could be prevented by ES936 pretreatment. The MDA468/NQ16 cells were more sensitive to growth inhibition after treatment with the benzoquinone Ansamycins compared with the MDA468 cells; this increased sensitivity could be reduced by ES936 pretreatment. The increased duration of benzoquinone Ansamycin exposure showed increased potency and -fold inhibition in MDA468/NQ16 cells relative to the parental MDA468 cells. Computational-based molecular modeling studies displayed additional contacts between yeast Hsp90 and the hydroquinone Ansamycins, which translated to greater interaction energies compared with the corresponding benzoquinone Ansamycins. In conclusion, these studies show that the reduction of this series of benzoquinone Ansamycins by NQO1 generates the corresponding hydroquinone Ansamycins, which exhibit enhanced Hsp90 inhibition.
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molecular docking studies investigating the interaction of a series of benzoquinone Ansamycin hsp90 inhibitors with nad p h quinone oxidoreductase 1 nqo1
Cancer Research, 2006Co-Authors: Philip Reigan, David Siegel, David RossAbstract:Proc Amer Assoc Cancer Res, Volume 47, 2006 1941 The active form of NAD(P)H:quinone oxidoreductase (NQO1) is a homodimer, composed of 273 amino acid residues and one flavin adenine dinucleotide (FAD) cofactor constituting one redox centre per monomer. NQO1 catalyzes the NAD(P)H-dependent two-electron reduction of quinones to hydroquinones and is therefore involved in the reductive activation of a number of antitumor quinone-based compounds. The benzoquinone Ansamycin antibiotics are a class of anticancer agents that are capable of binding to and disrupting the function of Hsp90, leading to the depletion of multiple oncogenic client proteins. We have previously reported that NQO1 can reduce the benzoquinone Ansamycin, 17-allylamino-17-demethoxy-geldanamycin (17AAG), to the corresponding hydroquinone Ansamycin and that the hydroquinone form is a more potent Hsp90 inhibitor, when compared to the parent quinone. Here, we describe a computational-based molecular docking study of a series of benzoquinone Ansamycins, into the FADH2-site of the human NQO1 crystal structure (PDB: [1KBQ][1]). The series of benzoquinone Ansamycins examined in this study include GDM, 17AAG, 17AG, 17DMAG and 17AEP-GA. These benzoquinone Ansamycins were docked into the binding site of NQO1 in the trans -isomer conformation, generated from the GDM cis -isomer structure co-crystallized in the human Hsp90 crystal structure (PDB: [1YET][2]), by targeted molecular dynamics methods. Molecular docking simulations were performed using the Affinity module of Insight II (Accelrys Inc.), which rotates, translates and performs a conformational search of the benzoquinone Ansamycin ligand of interest in the context of the binding site of NQO1, using a Monte Carlo algorithm. The Affinity run results in a set of structures that fall within specified energetic and geometric criteria. The resulting set of structures, for each benzoquinone Ansamycin, were analyzed and scored by the total energy output by Affinity, the total interaction energy between the ligand and the protein evaluated using the Docking module, the Ludi Score3 of interaction, the number of hydrogen bonds between the protein and the ligand particularly between the amino acids Tyr126 and Tyr128 and the C21 carbonyl of the quinone and that the quinone moiety of the benzoquinone Ansamycin is positioned parallel to the si -face of the isoalloxazine ring system of the FADH2 cofactor. These docking studies support that NQO1 can accommodate the benzoquinone Ansamycins as substrates for reduction to the corresponding hydroquinone Ansamycin. In addition, the scoring of the series of benzoquinone Ansamycins in this docking study correlated with their relative biochemical reduction rate data using purified recombinant human NQO1 (Supported by CA51210). [1]: /lookup/external-ref?link_type=PDB&access_num=1KBQ&atom=%2Fcanres%2F66%2F8_Supplement%2F457.3.atom [2]: /lookup/external-ref?link_type=PDB&access_num=1YET&atom=%2Fcanres%2F66%2F8_Supplement%2F457.3.atom
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targeted discovery of pentaketide Ansamycin aminoAnsamycinsa g
Organic Letters, 2019Co-Authors: Zishen Wang, Chunhua Lu, Yaoyao Li, Haoxin Wang, Yuemao ShenAbstract:Ansamycins are a class of macrolactams with diverse bioactivities, characterized by the unique 3-amino-5-hydroxybenzoic acid moiety. In this study, the Ansamycin gene cluster aas in Streptomyces sp. S35 was activated by the constitutive coexpression of two pathway-specific regulator genes aas1 and aas10, and seven novel pentaketide Ansamycin aminoAnsamycins A–G (1–7) were identified. Compound 4 with better antiproliferative activity indicated that the anthranilate analogues are probably promising building blocks for the production of unnatural Ansamycins with improved activity.
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Targeted Discovery of Pentaketide Ansamycin AminoAnsamycinsA–G
Organic Letters, 2019Co-Authors: Zishen Wang, Chunhua Lu, Yaoyao Li, Haoxin Wang, Yuemao ShenAbstract:Ansamycins are a class of macrolactams with diverse bioactivities, characterized by the unique 3-amino-5-hydroxybenzoic acid moiety. In this study, the Ansamycin gene cluster aas in Streptomyces sp. S35 was activated by the constitutive coexpression of two pathway-specific regulator genes aas1 and aas10, and seven novel pentaketide Ansamycin aminoAnsamycins A–G (1–7) were identified. Compound 4 with better antiproliferative activity indicated that the anthranilate analogues are probably promising building blocks for the production of unnatural Ansamycins with improved activity.
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pentaketide Ansamycin microAnsamycins a i from micromonospora sp reveal diverse post pks modifications
Organic Letters, 2018Co-Authors: Jianxiong Wang, Haoxin Wang, Wen Li, Chunhua LuAbstract:Overexpression of the pathway-specific positive regulator gene mas13 activated the cryptic gene cluster mas, resulting in the isolation of nine novel pentaketide Ansamycins, namely, microAnsamycins A–I (1–9). These results not only revealed a biosynthetic gene cluster of pentaketide Ansamycins for the first time but also presented an unprecedented scenario of diverse post-PKS modifications in Ansamycin biosynthesis.
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Pentaketide Ansamycin MicroAnsamycins A–I from Micromonospora sp. Reveal Diverse Post-PKS Modifications
Organic Letters, 2018Co-Authors: Jianxiong Wang, Haoxin Wang, Wen Li, Chunhua LuAbstract:Overexpression of the pathway-specific positive regulator gene mas13 activated the cryptic gene cluster mas, resulting in the isolation of nine novel pentaketide Ansamycins, namely, microAnsamycins A–I (1–9). These results not only revealed a biosynthetic gene cluster of pentaketide Ansamycins for the first time but also presented an unprecedented scenario of diverse post-PKS modifications in Ansamycin biosynthesis.
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activating a cryptic Ansamycin biosynthetic gene cluster to produce three new naphthalenic octaketide Ansamycins with n pentyl and n butyl side chains
Organic Letters, 2015Co-Authors: Shanren Li, Chunhua Lu, Yaoyao Li, Haoxin Wang, Juanli Zhang, Yuemao ShenAbstract:Genome mining is a rational approach to discovering new natural products. The genome sequence analysis of Streptomyces sp. LZ35 revealed the presence of a putative Ansamycin gene cluster (nam). Constitutive overexpression of the pathway-specific transcriptional regulatory gene nam1 successfully activated the nam gene cluster, and three novel naphthalenic octaketide Ansamycins were discovered with unprecedented n-pentylmalonyl-CoA or n-butylmalonyl-CoA extender units. This study represents the first example of discovering novel Ansamycin scaffolds via activation of a cryptic gene cluster.
