L’invention concerne des composes inhibiteurs de la Chk2 et leurs derives, et des methodes pour t... more L’invention concerne des composes inhibiteurs de la Chk2 et leurs derives, et des methodes pour traiter ou prevenir des maladies et des symptomes de maladies au moyen de leurs composes et compositions.
L'invention concerne une methode de traitement d'une infection par le virus de l'hepa... more L'invention concerne une methode de traitement d'une infection par le virus de l'hepatite C chez un patient, ladite methode consistant a fournir une quantite therapeutiquement efficace, a un patient qui en a besoin, d'un compose de la formule (I) ou d'un sel de qualite pharmaceutique de celui-ci. Dans ladite formule : G 1 est un groupe de la formule, n est 0, 1, 2, 3 ou 4 et Het est un groupe heteroaryle a 5 ou 6 elements contenant 1 a 4 heteroatomes independamment choisis parmi N, O et S, ledit Het etant eventuellement substitue.
Chk2 is a multi-substrate kinase involved in the DNA damage response and genomic stability. Part ... more Chk2 is a multi-substrate kinase involved in the DNA damage response and genomic stability. Part of the ATM-Chk2-p53 axis, it is also activated in various malignant tumors, possibly in a “gene addiction” context. Chk2 inhibitors are in development as anticancer agents based on their selectivity for enhancing the activity of DNA targeting agents in p53-deficient tumors. Here we determined the activation of Chk2, its protein and gene expression levels, and the activity of PV1019 (a new and specific Chk2 inhibitor; see abstract by Jobson et al.) across the 60 lines of the NCI DTP screen. Chk2 expression data were obtained from five microarray platforms (Affymetrix HG-U95, U133, U133 Plus 2.0, HuEx 1.0, and Agilent WHG). Levels of total and activated Chk2 (i.e., phosphorylated on threonine 68) were analyzed by Western blotting. PV1019 was tested in duplicate, and GI50 was interpolated from five serial dilutions of the drug. Our analyses demonstrate that a number of cell lines have high ...
Progress in Nucleic Acid Research and Molecular Biology, 2006
Topoisomerase I (Top1) is an abundant and essential enzyme. Top1 is the selective target of campt... more Topoisomerase I (Top1) is an abundant and essential enzyme. Top1 is the selective target of camptothecins, which are effective anticancer agents. Top1-DNA cleavage complexes can also be trapped by various endogenous and exogenous DNA lesions including mismatches, abasic sites and carcinogenic adducts. Tyrosyl-DNA phosphodiesterase (Tdp1) is one of the repair enzymes for Top1-DNA covalent complexes. Tdp1 forms a multiprotein complex that includes poly(ADP) ribose polymerase (PARP). PARP-deficient cells are hypersensitive to camptothecins and functionally deficient for Tdp1. We will review recent developments in several pathways involved in the repair of Top1 cleavage complexes and the role of Chk1 and Chk2 checkpoint kinases in the cellular responses to Top1 inhibitors. The genes conferring camptothecin hypersensitivity are compiled for humans, budding yeast and fission yeast. A. Introduction: Mammalian Topoisomerase Families, Top1 Functions and Catalytic Mechanisms Seven topoisomerase genes are encoded in the human nuclear genome [1]. The enzymes (abbreviated Topo or Top) have been numbered in the order of their discovery except for the most recent enzyme, mitochondrial topoisomerase I (Top1mt) [2,3]. Vertebrate cells contain two Top1 (Top1 for the nuclear genome and Top1mt for the mitochondrial genome), two Top2 (Top2α and β) and two Top3 (Top3α and β). The seventh topoisomerase is Spo11, whose expression is restricted to germ cells. Top3α forms heterodimers with BLM (the gene product deficient in Bloom syndrome) and is functionally related to the resolution of post-replicative hemicatenanes and recombination intermediates [4,5]. Top1 proteins belong to the family of the tyrosine recombinases (which includes λ-integrase, Flip and Cre recombinases), and Top2 is related to bacterial gyrase and Topo IV, which are the targets of quinolone antibiotics. Topoisomerases and tyrosine recombinases nick and religate DNA by forming a covalent enzyme-DNA intermediate between an enzyme catalytic tyrosine residue and the end of the broken DNA (Fig. 1). These covalent intermediates are generally referred to as "cleavage (or cleavable) complexes" (Fig. 2). Topoisomerases have also been classified in two groups depending whether they cleave and religate one strand (type I) or both strands (type II) of the DNA duplex. Type I enzymes include Top1 (nuclear), Top1mt, Top3α and β and type II enzymes include Top2α and β and Spo11. Top1 is essential in vertebrates and flies but not in yeast. Knocking out the TOP1 gene results in early embryonic lethality in mouse [6] and fly [7]. By contrast, yeast survives in the absence *To whom reprint requests should be addressed,
Checkpoint kinase 2 (Chk2), a ser/thr kinase involved in the ATM-Chk2 checkpoint pathway, is acti... more Checkpoint kinase 2 (Chk2), a ser/thr kinase involved in the ATM-Chk2 checkpoint pathway, is activated by genomic instability and DNA damage and results in either arrest of the cell cycle to allow DNA repair to occur or apoptosis if the DNA damage is severe. Drugs that specifically target Chk2 could be beneficial when administered in combination with current DNAdamaging agents used in cancer therapy. Recently, a novel inhibitor of Chk2, NSC 109555, was identified that exhibited high potency (IC 50 = 240 nM) and selectivity. This compound represents a new chemotype and lead for the development of novel Chk2 inhibitors that could be used as therapeutic agents for the treatment of cancer. To facilitate the discovery of new analogs of NSC 109555 with even greater potency and selectivity, we have solved the crystal structure of this inhibitor in complex with the catalytic domain of Chk2. The structure confirms that the compound is an ATP-competitive inhibitor, as the electron density clearly reveals that it occupies the ATPbinding pocket. However, the mode of inhibition differs from that of the previously studied structure of Chk2 in complex with debromohymenialdisine, a compound that inhibits both Chk1 and Chk2. A unique hydrophobic pocket in Chk2, located very close to the bound inhibitor, presents an opportunity for the rational design of compounds with higher binding affinity and greater selectivity.
DNA topoisomerase I (Top1) is the target of camptothecin and novel Top1 inhibitors are in develop... more DNA topoisomerase I (Top1) is the target of camptothecin and novel Top1 inhibitors are in development as anticancer agents. Top1 inhibitors damage DNA by trapping covalent complexes between the Top1 catalytic tyrosine and the 3'-end of the broken DNA. Tyrosyl-DNA phosphodiesterase (Tdp1) can repair Top1-DNA covalent complexes by hydrolyzing the tyrosyl-DNA bond. Inhibiting Tdp1 has the potential to enhance the anticancer activity of Top1 inhibitors (http://discover.nci.nih.gov/pommier/pommier.htm) and to act as antiproliferative agents. In the present study, we report that neomycin inhibits Tdp1 more effectively than the related aminoglycosides paromomycin and lividomycin A. Inhibition of Tdp1 by neomycin is observed both with single-and doublestranded substrates but is slightly stronger with duplex DNA, which is different from aclarubcin, which only inhibits Tdp1 with the single-stranded substrate. Inhibition by neomycin can be overcome with excess Tdp1 and is greatest at low pH. To our knowledge, aminoglycoside antibiotics and the ribosome inhibitors thiostrepton, clindamycin-2-phosphate and puromycin are the first reported pharmacological Tdp1 inhibitors.
Chk2 is a protein kinase involved in the ATM-dependent checkpoint pathway (http://discover.nci.ni... more Chk2 is a protein kinase involved in the ATM-dependent checkpoint pathway (http://discover.nci.nih.gov/mim). This pathway is activated by genomic instability and DNA damage and results in either cell cycle arrest to allow DNA repair to occur, or cell death (apoptosis). Chk2 is activated by ATM-mediated phosphorylation and autophosphorylation, and in turn phosphorylates its downstream targets (Cdc25A, Cdc25C, BRCA1, p53, Hdmx, E2F1, PP2A and PML). Inhibition of Chk2 has been proposed to sensitize p53-deficient cells, as well as protect normal tissue following exposure to DNA-damaging agents. We have developed a drug-screening program for specific Chk2 inhibitors using a fluorescence polarization assay, IMAP. This assay detects the degree of phosphorylation of a fluorescently-linked substrate by Chk2. From a screen of over 100,000 compounds from the NCI Developmental Therapeutics Program (DTP), we identified a bis-guanylhydrazone (NSC 109555) as a lead compound. In vitro data show the specific inhibition of Chk2 kinase activity by NSC 109555 using in vitro kinase assays and kinase-profiling experiments. NSC 109555 was shown to be a competitive inhibitor of Chk2 with respect to ATP, which was supported by docking of NSC 109555 into the ATP binding pocket of the Chk2 catalytic domain. The potency of NSC 109555 was comparable to other known Chk2 inhibitors, DBH (debromohymenialdisine) and 2-arylbenzimidazole. These data define a novel chemotype for the development of potent and selective inhibitors of Chk2. Ultimately this class of drugs may be useful in combination with current DNA-damaging agents used in the clinic.
Chk2 is a checkpoint kinase involved in the ATM pathway, which is activated by genomic instabilit... more Chk2 is a checkpoint kinase involved in the ATM pathway, which is activated by genomic instability and DNA damage, leading to either cell death (apoptosis) or cell cycle arrest. Chk2 provides an unexplored therapeutic target against cancer cells. We recently reported NSC 109555 as a novel chemotype Chk2 inhibitor. We have now synthesized a derivative of NSC 109555, PV1019 (NSC 744039), which is a selective sub-micromolar inhibitor of Chk2 in vitro. The co-crystal structure of PV1019 bound in the ATP binding pocket of Chk2 confirmed enzymatic/biochemical observations that PV1019 acts as a competitive inhibitor of Chk2 with respect to ATP. PV1019 was found to inhibit Chk2 in cells. It inhibits Chk2 autophosphorylation (which represents the cellular kinase activation of Chk2), Cdc25C phosphorylation, and HDMX degradation in response to DNA damage. PV1019 also protects normal mouse thymocytes against IR-induced apoptosis, and it shows synergistic antiproliferative activity with topoteca...
Chk2 (checkpoint kinase 2) is a serine/threonine kinase that participates in a series of signalin... more Chk2 (checkpoint kinase 2) is a serine/threonine kinase that participates in a series of signaling networks responsible for maintaining genomic integrity and responding to DNA damage. The development of selective Chk2 inhibitors has recently attracted much interest as a means of sensitizing cancer cells to current DNA-damaging agents used in the treatment of cancer. Additionally, selective Chk2 inhibitors may reduce p53-mediated apoptosis in normal tissues, thereby helping to mitigate adverse side effects from chemotherapy and radiation. Thus far, relatively few selective inhibitors of Chk2 have been described and none have yet progressed into clinical trials. Here, we report crystal structures of the catalytic domain of Chk2 in complex with a novel series of potent and selective small molecule inhibitors. These compounds exhibit nanomolar potencies and are selective for Chk2 over Chk1. The structures reported here elucidate the binding modes of these inhibitors to Chk2 and provide information that can be exploited for the structure-assisted design of novel chemotherapeutics.
Journal of Pharmacology and Experimental Therapeutics, 2009
Chk2 is a checkpoint kinase involved in the ataxia telangiectasia mutated pathway, which is activ... more Chk2 is a checkpoint kinase involved in the ataxia telangiectasia mutated pathway, which is activated by genomic instability and DNA damage, leading to either cell death (apoptosis) or cell cycle arrest. Chk2 provides an unexplored therapeutic target against cancer cells. We recently reported 4,4Ј-diacetyldiphenylurea-bis(guanylhydrazone) (NSC 109555) as a novel chemotype Chk2 inhibitor. We have now synthesized a derivative of NSC 109555, PV1019 (NSC 744039) [7-nitro-1H-indole-2-carboxylic acid {4-[1-(guanidinohydrazone)-ethyl]-phenyl}-amide], which is a selective submicromolar inhibitor of Chk2 in vitro. The cocrystal structure of PV1019 bound in the ATP binding pocket of Chk2 confirmed enzymatic/biochemical observations that PV1019 acts as a competitive inhibitor of Chk2 with respect to ATP. PV1019 was found to inhibit Chk2 in cells. It inhibits Chk2 autophosphorylation (which represents the cellular kinase activation of Chk2), Cdc25C phosphorylation, and HDMX degradation in response to DNA damage. PV1019 also protects normal mouse thymocytes against ionizing radiationinduced apoptosis, and it shows synergistic antiproliferative activity with topotecan, camptothecin, and radiation in human tumor cell lines. We also show that PV1019 and Chk2 small interfering RNAs can exert antiproliferative activity themselves in the cancer cells with high Chk2 expression in the NCI-60 screen. These data indicate that PV1019 is a potent and selective inhibitor of Chk2 with chemotherapeutic and radiosensitization potential.
Recent data suggest that curcumin, a phytochemical with cancer chemopreventive potential, might b... more Recent data suggest that curcumin, a phytochemical with cancer chemopreventive potential, might be useful in the treatment of several solid and hematological malignancies. DNA topoisomerases (topos) are the target of several drugs commonly used in cancer chemotherapy. These drugs induce topo-DNA complexes with either topo I or topo II; then cellular processing converts these complexes into permanent DNA strand breaks that trigger cell death. Using the TARDIS in vivo assay, this study shows for the first time that curcumin induces topo I and topo II (R and)-DNA complexes in K562 leukemia cells. A comparative analysis revealed that the levels of these complexes were higher than those induced by several standard topo I and topo II inhibitors at equitoxic doses. Curcumin-induced topo I and topo II-DNA complexes were prevented by the antioxidant N-acetylcysteine; this suggests that, unlike the standard topo inhibitors, reactive oxygen species may mediate the formation of these complexes. Overall, this work shows that curcumin is capable of inducing topo-DNA complexes in cells with both topo I and topo II and increases the evidence suggesting that this dietary agent has potential to be tested in cancer chemotherapy.
L’invention concerne des composes inhibiteurs de la Chk2 et leurs derives, et des methodes pour t... more L’invention concerne des composes inhibiteurs de la Chk2 et leurs derives, et des methodes pour traiter ou prevenir des maladies et des symptomes de maladies au moyen de leurs composes et compositions.
L'invention concerne une methode de traitement d'une infection par le virus de l'hepa... more L'invention concerne une methode de traitement d'une infection par le virus de l'hepatite C chez un patient, ladite methode consistant a fournir une quantite therapeutiquement efficace, a un patient qui en a besoin, d'un compose de la formule (I) ou d'un sel de qualite pharmaceutique de celui-ci. Dans ladite formule : G 1 est un groupe de la formule, n est 0, 1, 2, 3 ou 4 et Het est un groupe heteroaryle a 5 ou 6 elements contenant 1 a 4 heteroatomes independamment choisis parmi N, O et S, ledit Het etant eventuellement substitue.
Chk2 is a multi-substrate kinase involved in the DNA damage response and genomic stability. Part ... more Chk2 is a multi-substrate kinase involved in the DNA damage response and genomic stability. Part of the ATM-Chk2-p53 axis, it is also activated in various malignant tumors, possibly in a “gene addiction” context. Chk2 inhibitors are in development as anticancer agents based on their selectivity for enhancing the activity of DNA targeting agents in p53-deficient tumors. Here we determined the activation of Chk2, its protein and gene expression levels, and the activity of PV1019 (a new and specific Chk2 inhibitor; see abstract by Jobson et al.) across the 60 lines of the NCI DTP screen. Chk2 expression data were obtained from five microarray platforms (Affymetrix HG-U95, U133, U133 Plus 2.0, HuEx 1.0, and Agilent WHG). Levels of total and activated Chk2 (i.e., phosphorylated on threonine 68) were analyzed by Western blotting. PV1019 was tested in duplicate, and GI50 was interpolated from five serial dilutions of the drug. Our analyses demonstrate that a number of cell lines have high ...
Progress in Nucleic Acid Research and Molecular Biology, 2006
Topoisomerase I (Top1) is an abundant and essential enzyme. Top1 is the selective target of campt... more Topoisomerase I (Top1) is an abundant and essential enzyme. Top1 is the selective target of camptothecins, which are effective anticancer agents. Top1-DNA cleavage complexes can also be trapped by various endogenous and exogenous DNA lesions including mismatches, abasic sites and carcinogenic adducts. Tyrosyl-DNA phosphodiesterase (Tdp1) is one of the repair enzymes for Top1-DNA covalent complexes. Tdp1 forms a multiprotein complex that includes poly(ADP) ribose polymerase (PARP). PARP-deficient cells are hypersensitive to camptothecins and functionally deficient for Tdp1. We will review recent developments in several pathways involved in the repair of Top1 cleavage complexes and the role of Chk1 and Chk2 checkpoint kinases in the cellular responses to Top1 inhibitors. The genes conferring camptothecin hypersensitivity are compiled for humans, budding yeast and fission yeast. A. Introduction: Mammalian Topoisomerase Families, Top1 Functions and Catalytic Mechanisms Seven topoisomerase genes are encoded in the human nuclear genome [1]. The enzymes (abbreviated Topo or Top) have been numbered in the order of their discovery except for the most recent enzyme, mitochondrial topoisomerase I (Top1mt) [2,3]. Vertebrate cells contain two Top1 (Top1 for the nuclear genome and Top1mt for the mitochondrial genome), two Top2 (Top2α and β) and two Top3 (Top3α and β). The seventh topoisomerase is Spo11, whose expression is restricted to germ cells. Top3α forms heterodimers with BLM (the gene product deficient in Bloom syndrome) and is functionally related to the resolution of post-replicative hemicatenanes and recombination intermediates [4,5]. Top1 proteins belong to the family of the tyrosine recombinases (which includes λ-integrase, Flip and Cre recombinases), and Top2 is related to bacterial gyrase and Topo IV, which are the targets of quinolone antibiotics. Topoisomerases and tyrosine recombinases nick and religate DNA by forming a covalent enzyme-DNA intermediate between an enzyme catalytic tyrosine residue and the end of the broken DNA (Fig. 1). These covalent intermediates are generally referred to as "cleavage (or cleavable) complexes" (Fig. 2). Topoisomerases have also been classified in two groups depending whether they cleave and religate one strand (type I) or both strands (type II) of the DNA duplex. Type I enzymes include Top1 (nuclear), Top1mt, Top3α and β and type II enzymes include Top2α and β and Spo11. Top1 is essential in vertebrates and flies but not in yeast. Knocking out the TOP1 gene results in early embryonic lethality in mouse [6] and fly [7]. By contrast, yeast survives in the absence *To whom reprint requests should be addressed,
Checkpoint kinase 2 (Chk2), a ser/thr kinase involved in the ATM-Chk2 checkpoint pathway, is acti... more Checkpoint kinase 2 (Chk2), a ser/thr kinase involved in the ATM-Chk2 checkpoint pathway, is activated by genomic instability and DNA damage and results in either arrest of the cell cycle to allow DNA repair to occur or apoptosis if the DNA damage is severe. Drugs that specifically target Chk2 could be beneficial when administered in combination with current DNAdamaging agents used in cancer therapy. Recently, a novel inhibitor of Chk2, NSC 109555, was identified that exhibited high potency (IC 50 = 240 nM) and selectivity. This compound represents a new chemotype and lead for the development of novel Chk2 inhibitors that could be used as therapeutic agents for the treatment of cancer. To facilitate the discovery of new analogs of NSC 109555 with even greater potency and selectivity, we have solved the crystal structure of this inhibitor in complex with the catalytic domain of Chk2. The structure confirms that the compound is an ATP-competitive inhibitor, as the electron density clearly reveals that it occupies the ATPbinding pocket. However, the mode of inhibition differs from that of the previously studied structure of Chk2 in complex with debromohymenialdisine, a compound that inhibits both Chk1 and Chk2. A unique hydrophobic pocket in Chk2, located very close to the bound inhibitor, presents an opportunity for the rational design of compounds with higher binding affinity and greater selectivity.
DNA topoisomerase I (Top1) is the target of camptothecin and novel Top1 inhibitors are in develop... more DNA topoisomerase I (Top1) is the target of camptothecin and novel Top1 inhibitors are in development as anticancer agents. Top1 inhibitors damage DNA by trapping covalent complexes between the Top1 catalytic tyrosine and the 3'-end of the broken DNA. Tyrosyl-DNA phosphodiesterase (Tdp1) can repair Top1-DNA covalent complexes by hydrolyzing the tyrosyl-DNA bond. Inhibiting Tdp1 has the potential to enhance the anticancer activity of Top1 inhibitors (http://discover.nci.nih.gov/pommier/pommier.htm) and to act as antiproliferative agents. In the present study, we report that neomycin inhibits Tdp1 more effectively than the related aminoglycosides paromomycin and lividomycin A. Inhibition of Tdp1 by neomycin is observed both with single-and doublestranded substrates but is slightly stronger with duplex DNA, which is different from aclarubcin, which only inhibits Tdp1 with the single-stranded substrate. Inhibition by neomycin can be overcome with excess Tdp1 and is greatest at low pH. To our knowledge, aminoglycoside antibiotics and the ribosome inhibitors thiostrepton, clindamycin-2-phosphate and puromycin are the first reported pharmacological Tdp1 inhibitors.
Chk2 is a protein kinase involved in the ATM-dependent checkpoint pathway (http://discover.nci.ni... more Chk2 is a protein kinase involved in the ATM-dependent checkpoint pathway (http://discover.nci.nih.gov/mim). This pathway is activated by genomic instability and DNA damage and results in either cell cycle arrest to allow DNA repair to occur, or cell death (apoptosis). Chk2 is activated by ATM-mediated phosphorylation and autophosphorylation, and in turn phosphorylates its downstream targets (Cdc25A, Cdc25C, BRCA1, p53, Hdmx, E2F1, PP2A and PML). Inhibition of Chk2 has been proposed to sensitize p53-deficient cells, as well as protect normal tissue following exposure to DNA-damaging agents. We have developed a drug-screening program for specific Chk2 inhibitors using a fluorescence polarization assay, IMAP. This assay detects the degree of phosphorylation of a fluorescently-linked substrate by Chk2. From a screen of over 100,000 compounds from the NCI Developmental Therapeutics Program (DTP), we identified a bis-guanylhydrazone (NSC 109555) as a lead compound. In vitro data show the specific inhibition of Chk2 kinase activity by NSC 109555 using in vitro kinase assays and kinase-profiling experiments. NSC 109555 was shown to be a competitive inhibitor of Chk2 with respect to ATP, which was supported by docking of NSC 109555 into the ATP binding pocket of the Chk2 catalytic domain. The potency of NSC 109555 was comparable to other known Chk2 inhibitors, DBH (debromohymenialdisine) and 2-arylbenzimidazole. These data define a novel chemotype for the development of potent and selective inhibitors of Chk2. Ultimately this class of drugs may be useful in combination with current DNA-damaging agents used in the clinic.
Chk2 is a checkpoint kinase involved in the ATM pathway, which is activated by genomic instabilit... more Chk2 is a checkpoint kinase involved in the ATM pathway, which is activated by genomic instability and DNA damage, leading to either cell death (apoptosis) or cell cycle arrest. Chk2 provides an unexplored therapeutic target against cancer cells. We recently reported NSC 109555 as a novel chemotype Chk2 inhibitor. We have now synthesized a derivative of NSC 109555, PV1019 (NSC 744039), which is a selective sub-micromolar inhibitor of Chk2 in vitro. The co-crystal structure of PV1019 bound in the ATP binding pocket of Chk2 confirmed enzymatic/biochemical observations that PV1019 acts as a competitive inhibitor of Chk2 with respect to ATP. PV1019 was found to inhibit Chk2 in cells. It inhibits Chk2 autophosphorylation (which represents the cellular kinase activation of Chk2), Cdc25C phosphorylation, and HDMX degradation in response to DNA damage. PV1019 also protects normal mouse thymocytes against IR-induced apoptosis, and it shows synergistic antiproliferative activity with topoteca...
Chk2 (checkpoint kinase 2) is a serine/threonine kinase that participates in a series of signalin... more Chk2 (checkpoint kinase 2) is a serine/threonine kinase that participates in a series of signaling networks responsible for maintaining genomic integrity and responding to DNA damage. The development of selective Chk2 inhibitors has recently attracted much interest as a means of sensitizing cancer cells to current DNA-damaging agents used in the treatment of cancer. Additionally, selective Chk2 inhibitors may reduce p53-mediated apoptosis in normal tissues, thereby helping to mitigate adverse side effects from chemotherapy and radiation. Thus far, relatively few selective inhibitors of Chk2 have been described and none have yet progressed into clinical trials. Here, we report crystal structures of the catalytic domain of Chk2 in complex with a novel series of potent and selective small molecule inhibitors. These compounds exhibit nanomolar potencies and are selective for Chk2 over Chk1. The structures reported here elucidate the binding modes of these inhibitors to Chk2 and provide information that can be exploited for the structure-assisted design of novel chemotherapeutics.
Journal of Pharmacology and Experimental Therapeutics, 2009
Chk2 is a checkpoint kinase involved in the ataxia telangiectasia mutated pathway, which is activ... more Chk2 is a checkpoint kinase involved in the ataxia telangiectasia mutated pathway, which is activated by genomic instability and DNA damage, leading to either cell death (apoptosis) or cell cycle arrest. Chk2 provides an unexplored therapeutic target against cancer cells. We recently reported 4,4Ј-diacetyldiphenylurea-bis(guanylhydrazone) (NSC 109555) as a novel chemotype Chk2 inhibitor. We have now synthesized a derivative of NSC 109555, PV1019 (NSC 744039) [7-nitro-1H-indole-2-carboxylic acid {4-[1-(guanidinohydrazone)-ethyl]-phenyl}-amide], which is a selective submicromolar inhibitor of Chk2 in vitro. The cocrystal structure of PV1019 bound in the ATP binding pocket of Chk2 confirmed enzymatic/biochemical observations that PV1019 acts as a competitive inhibitor of Chk2 with respect to ATP. PV1019 was found to inhibit Chk2 in cells. It inhibits Chk2 autophosphorylation (which represents the cellular kinase activation of Chk2), Cdc25C phosphorylation, and HDMX degradation in response to DNA damage. PV1019 also protects normal mouse thymocytes against ionizing radiationinduced apoptosis, and it shows synergistic antiproliferative activity with topotecan, camptothecin, and radiation in human tumor cell lines. We also show that PV1019 and Chk2 small interfering RNAs can exert antiproliferative activity themselves in the cancer cells with high Chk2 expression in the NCI-60 screen. These data indicate that PV1019 is a potent and selective inhibitor of Chk2 with chemotherapeutic and radiosensitization potential.
Recent data suggest that curcumin, a phytochemical with cancer chemopreventive potential, might b... more Recent data suggest that curcumin, a phytochemical with cancer chemopreventive potential, might be useful in the treatment of several solid and hematological malignancies. DNA topoisomerases (topos) are the target of several drugs commonly used in cancer chemotherapy. These drugs induce topo-DNA complexes with either topo I or topo II; then cellular processing converts these complexes into permanent DNA strand breaks that trigger cell death. Using the TARDIS in vivo assay, this study shows for the first time that curcumin induces topo I and topo II (R and)-DNA complexes in K562 leukemia cells. A comparative analysis revealed that the levels of these complexes were higher than those induced by several standard topo I and topo II inhibitors at equitoxic doses. Curcumin-induced topo I and topo II-DNA complexes were prevented by the antioxidant N-acetylcysteine; this suggests that, unlike the standard topo inhibitors, reactive oxygen species may mediate the formation of these complexes. Overall, this work shows that curcumin is capable of inducing topo-DNA complexes in cells with both topo I and topo II and increases the evidence suggesting that this dietary agent has potential to be tested in cancer chemotherapy.
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Papers by Andrew Jobson