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Hande S, Goswami K, Sharma R, Bhoj P, Jena L, Reddy MVR. Targeting folate metabolism for therapeutic option: A bioinformatics approach. Indian J Exp Biol 2015; 53:762-766. [PMID: 26669020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Lymphatic filariasis, commonly called elephantiasis, poses a burden of estimated level of 5.09 million disability adjusted life year. Limitations of its sole drug, diethylcarbamazine (DEC) drive exploration of effective filarial target. A few plant extracts having polyphenolic ingredients and some synthetic compounds possess potential dihydrofolate reductase (DHFR) inhibitory effect. Here, we postulated a plausible link between folates and polyphenolics based on their common precursor in shikimate metabolism. Considering its implication in structural resemblance based antagonism, we have attempted to validate parasitic DHFR protein as a target. The bioinformatics approach, in the absence of crystal structure of the proposed target, used to authenticate and for virtual docking with suitable tested compounds, showed remarkably lower thermodynamic parameters as opposed to the positive control. A comparative docking analysis between human and Brugia malayi DHFR also showed effective binding parameters with lower inhibition constants of these ligands with parasitic target, but not with human counterpart highlighting safety and efficacy. This study suggests that DHFR could be a valid drug target for lymphatic filariasis, and further reveal that bioinformatics may be an effective tool in reverse pharmacological approach for drug design.
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G-Dayanandan N, Paulsen JL, Viswanathan K, Keshipeddy S, Lombardo M, Zhou W, Lamb KM, Sochia AE, Alverson JB, Priestley ND, Wright DL, Anderson AC. Propargyl-linked antifolates are dual inhibitors of Candida albicans and Candida glabrata. J Med Chem 2014; 57:2643-56. [PMID: 24568657 PMCID: PMC3983340 DOI: 10.1021/jm401916j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Indexed: 02/05/2023]
Abstract
Species of Candida, primarily C. albicans and with increasing prevalence, C. glabrata, are responsible for the majority of fungal bloodstream infections that cause morbidity, especially among immune compromised patients. While the development of new antifungal agents that target the essential enzyme, dihydrofolate reductase (DHFR), in both Candida species would be ideal, previous attempts have resulted in antifolates that exhibit inconsistencies between enzyme inhibition and antifungal properties. In this article, we describe the evaluation of pairs of propargyl-linked antifolates that possess similar physicochemical properties but different shapes. All of these compounds are effective at inhibiting the fungal enzymes and the growth of C. glabrata; however, the inhibition of the growth of C. albicans is shape-dependent with extended para-linked compounds proving more effective than compact, meta-linked compounds. Using crystal structures of DHFR from C. albicans and C. glabrata bound to lead compounds, 13 new para-linked compounds designed to inhibit both species were synthesized. Eight of these compounds potently inhibit the growth of both fungal species with three compounds displaying dual MIC values less than 1 μg/mL. Analysis of the active compounds shows that shape and distribution of polar functionality is critical in achieving dual antifungal activity.
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Affiliation(s)
- Narendran G-Dayanandan
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
| | - Janet L. Paulsen
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
| | - Kishore Viswanathan
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
| | - Santosh Keshipeddy
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
| | - Michael
N. Lombardo
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
| | - Wangda Zhou
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
| | - Kristen M. Lamb
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
| | - Adrienne E. Sochia
- Department
of Chemistry, University of Montana, Missoula, Montana 59812, United States
| | - Jeremy B. Alverson
- Department
of Chemistry, University of Montana, Missoula, Montana 59812, United States
| | - Nigel D. Priestley
- Department
of Chemistry, University of Montana, Missoula, Montana 59812, United States
| | - Dennis L. Wright
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
| | - Amy C. Anderson
- Department
of Pharmaceutical Sciences, University of
Connecticut, 69 N. Eagleville
Road, Storrs, Connecticut 06269, United States
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Gangjee A, Li W, Lin L, Zeng Y, Ihnat M, Warnke LA, Green DW, Cody V, Pace J, Queener SF. Design, synthesis, and X-ray crystal structures of 2,4-diaminofuro[2,3-d]pyrimidines as multireceptor tyrosine kinase and dihydrofolate reductase inhibitors. Bioorg Med Chem 2009; 17:7324-36. [PMID: 19748785 PMCID: PMC2779540 DOI: 10.1016/j.bmc.2009.08.044] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Revised: 08/17/2009] [Accepted: 08/18/2009] [Indexed: 11/24/2022]
Abstract
To optimize dual receptor tyrosine kinase (RTK) and dihydrofolate reductase (DHFR) inhibition, the E- and Z-isomers of 5-[2-(2-methoxyphenyl)prop-1-en-1-yl]furo[2,3-d]pyrimidine-2,4-diamines (1a and 1b) were separated by HPLC and the X-ray crystal structures (2.0 and 1.4A, respectively) with mouse DHFR and NADPH as well as 1b with human DHFR (1.5A) were determined. The E- and Z-isomers adopt different binding modes when bound to mouse DHFR. A series of 2,4-diaminofuro[2,3-d]pyrimidines 2-13 were designed and synthesized using the X-ray crystal structures of 1a and 1b with DHFR to increase their DHFR inhibitory activity. Wittig reactions of appropriate 2-methoxyphenyl ketones with 2,4-diamino-6-chloromethyl furo[2,3-d]pyrimidine afforded the C8-C9 unsaturated compounds 2-7 and catalytic reduction gave the saturated 8-13. Homologation of the C9-methyl analog maintains DHFR inhibitory activity. In addition, inhibition of EGFR and PDGFR-beta were discovered for saturated C9-homologated analogs 9 and 10 that were absent in the saturated C9-methyl analogs.
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Affiliation(s)
- Aleem Gangjee
- Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA 15282, USA.
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Smith K, Ednie LM, Appelbaum PC, Hawser S, Lociuro S. Antistreptococcal activity of AR-709 compared to that of other agents. Antimicrob Agents Chemother 2008; 52:2279-82. [PMID: 18362189 PMCID: PMC2415763 DOI: 10.1128/aac.01620-07] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 03/12/2008] [Accepted: 03/15/2008] [Indexed: 11/20/2022] Open
Abstract
Against 300 strains of pneumococci and 100 group A streptococci of differing beta-lactam, macrolide, and quinolone resistance phenotypes, AR-709 was very active, with all MICs being < or =2 microg/ml. Furthermore, AR-709 was active against strains that were both susceptible and resistant to trimethoprim-sulfamethoxazole.
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Affiliation(s)
- Kathy Smith
- Department of Pathology, Hershey Medical Center, Hershey, PA 17033, USA
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Reynolds RC, Campbell SR, Fairchild RG, Kisliuk RL, Micca PL, Queener SF, Riordan JM, Sedwick WD, Waud WR, Leung AKW, Dixon RW, Suling WJ, Borhani DW. Novel boron-containing, nonclassical antifolates: synthesis and preliminary biological and structural evaluation. J Med Chem 2007; 50:3283-9. [PMID: 17569517 DOI: 10.1021/jm0701977] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two boron-containing, ortho-icosahedral carborane lipophilic antifolates were synthesized, and the crystal structures of their ternary complexes with human dihydrofolate reductase (DHFR) and dihydronicotinamide adenine dinucleotide phosphate were determined. The compounds were screened for activity against DHFR from six sources (human, rat liver, Pneumocystis carinii, Toxoplasma gondii, Mycobacterium avium, and Lactobacillus casei) and showed good to modest activity against these enzymes. The compounds were also tested for antibacterial activity against L. casei, M. tuberculosis H37Ra, and three M. avium strains and for cytotoxic activity against seven different human tumor cell lines. Antibacterial and cytotoxic activity was modest, with one sample, the closo-carborane 4, showing about 10-fold greater activity. The less toxic nido-carborane 2 was also tested as a candidate for boron neutron capture therapy, but showed poor tumor retention and low selectivity ratios for boron distribution in tumor tissue versus normal tissue.
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Affiliation(s)
- Robert C Reynolds
- Drug Discovery Division, Southern Research Institute, Birmingham, Alabama 35205, USA.
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Abstract
Sulpha drugs act as competitive inhibitors of p-amino benzoic acid, an intermediate in the de novo folate pathway. Dihydropteroate synthase condenses sulpha drugs into sulpha-dihydropteroate (sulpha-DHP), which competes with dihydrofolate, the dihydrofolate reductase (DHFR) substrate. This designates DHFR as a possible target of sulpha-DHP. We suggest here that Plasmodium vivax DHFR is indeed the in vivo target of sulpha drugs. The wild-type DHFR expressed in Saccharomyces cerevisiae leads to cell growth inhibition, while sensitivity to the drug is exacerbated in the mutants. Contrary to what is observed with sulphanilamide, methotrexate is less effective on P. vivax-DHFR mutants than on wild-type mutant.
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Affiliation(s)
- Liselotte Yimga Djapa
- Institut de Génétique et de Microbiologie, CNRS UMR 8621, Université Paris-Sud, Orsay Cedex, France
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Abstract
Drinking green tea is associated with decreased frequency of cancer development. This review outlines the wide range of mechanisms by which epigallocatechin gallate (ECGC) and other green and black tea polyphenols inhibit cancer cell survival. EGCG suppressed androgen receptor expression and signalling via several growth factor receptors. Cell cycle arrest or apoptosis involved caspase activation and altered Bcl-2 family member expression. EGCG inhibited telomerase activity and led to telomere fragmentation. While at high concentrations polyphenols had pro-oxidative activities, at much lower levels, anti-oxidative effects occurred. Nitric oxide production was reduced by EGCG and black tea theaflavins by suppressing inducible nitric oxide synthase via blocking nuclear translocation of the transcription factor nuclear factor-kappaB as a result of decreased IkappaB kinase activity. Polyphenols up- or down-regulated activity of a number of key enzymes, including mitogen-activated protein kinases and protein kinase C, and increased or decreased protein/mRNA levels, including that of cyclins, oncogenes, and tumor suppressor genes. Metastasis was inhibited via effects on urokinase and matrix metalloproteinases. Polyphenols reduced angiogenesis, in part by decreasing vascular endothelial growth factor production and receptor phosphorylation. Recent work demonstrated that EGCG reduced dihydrofolate reductase activity, which would affect nucleic acid and protein synthesis. It also acted as an aryl hydrocarbon receptor an-tagonist by directly binding the receptor's molecular chaperone, heat shock protein 90. In conclusion, green and black tea polyphenols act at numerous points regulating cancer cell growth, survival, and metastasis, including effects at the DNA, RNA, and protein levels.
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Affiliation(s)
- Lisa Ann Beltz
- Department of Biology, University of Northern Iowa, Cedar Falls, IA 50614, USA.
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Joska TM, Anderson AC. Structure-activity relationships of Bacillus cereus and Bacillus anthracis dihydrofolate reductase: toward the identification of new potent drug leads. Antimicrob Agents Chemother 2006; 50:3435-43. [PMID: 17005826 PMCID: PMC1610094 DOI: 10.1128/aac.00386-06] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
New and improved therapeutics are needed for Bacillus anthracis, the etiological agent of anthrax. To date, antimicrobial agents have not been developed against the well-validated target dihydrofolate reductase (DHFR). In order to address whether DHFR inhibitors could have potential use as clinical agents against Bacillus, 27 compounds were screened against this enzyme from Bacillus cereus, which is identical to the enzyme from B. anthracis at the active site. Several 2,4-diamino-5-deazapteridine compounds exhibit submicromolar 50% inhibitory concentrations (IC(50)s). Four of the inhibitors displaying potency in vitro were tested in vivo and showed a marked growth inhibition of B. cereus; the most potent of these has MIC(50) and minimum bactericidal concentrations at which 50% are killed of 1.6 mug/ml and 0.09 mug/ml, respectively. In order to illustrate structure-activity relationships for the classes of inhibitors tested, each of the 27 inhibitors was docked into homology models of the B. cereus and B. anthracis DHFR proteins, allowing the development of a rationale for the inhibition profiles. A combination of favorable interactions with the diaminopyrimidine and substituted phenyl rings explains the low IC(50) values of potent inhibitors; steric interactions explain higher IC(50) values. These experiments show that DHFR is a reasonable antimicrobial target for Bacillus anthracis and that there is a class of inhibitors that possess sufficient potency and antibacterial activity to suggest further development.
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Affiliation(s)
- Tammy M Joska
- Department of Biochemistry, University of Connecticut, Storrs, CT 06269, USA
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9
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Abstract
We present a new molecular design program, FlexNovo, for structure-based searching within large fragment spaces following a sequential growth strategy. The fragment spaces consist of several thousands of chemical fragments and a corresponding set of rules that specify how the fragments can be connected. FlexNovo is based on the FlexX molecular docking software and makes use of its incremental construction algorithm and the underlying chemical models. Interaction energies are calculated by using standard scoring functions. Several placement geometry, physicochemical property (drug-likeness), and diversity filter criteria are directly integrated into the "build-up" process. FlexNovo has been used to design potential inhibitors for four targets of pharmaceutical interest (dihydrofolate reductase, cyclin-dependant kinase 2, cyclooxygenase-2, and the estrogen receptor). We have carried out calculations using different diversity parameters for each of these targets and generated solution sets containing up to 50 molecules. The compounds obtained show that FlexNovo is able to generate a diverse set of reasonable molecules with drug-like properties. The results, including an automated similarity analysis with the Feature Tree program, indicate that FlexNovo often reproduces structural motifs as well as the corresponding binding modes seen in known active structures.
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Affiliation(s)
- Jörg Degen
- Center for Bioinformatics, ZBH, University of Hamburg, Bundesstrasse 43, 20146 Hamburg, Germany
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Bunyarataphan S, Leartsakulpanich U, Taweechai S, Tarnchompoo B, Kamchonwongpaisan S, Yuthavong Y. Evaluation of the activities of pyrimethamine analogs against Plasmodium vivax and Plasmodium falciparum dihydrofolate reductase-thymidylate synthase using in vitro enzyme inhibition and bacterial complementation assays. Antimicrob Agents Chemother 2006; 50:3631-7. [PMID: 16954316 PMCID: PMC1635237 DOI: 10.1128/aac.00448-06] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pyrimethamine analogs were examined as potential agents against vivax malaria using a bacterial surrogate system carrying Plasmodium vivax dihydrofolate reductase-thymidylate synthase (PvDHFR-TS), in which the PvDHFR complemented chemically knocked out host dihydrofolate reductase. The system was initially tested with P. falciparum dihydrofolate reductase-thymidylate synthase and was found to have good correlation with the parasite-based system. The 50% inhibitory concentrations derived from PvDHFR-TS-dependent bacteria were correlated with their corresponding inhibition constants (Ki) from an enzyme inhibition assay, pointing to the likelihood that the potent enzyme inhibitors will also have potent antimalarial activities. Active compounds against both wild-type and S58R S117N (SP21) double-mutant P. vivax include analogs with structures which can avert a steric clash with the asparagine (S117N) side chain of the mutant, similar to those found for homologous Plasmodium falciparum mutants, raising the possibility that the same compounds can be developed against both types of antifolate-resistant malaria. This rapid and convenient drug screening system should be useful for development of new antifolates against P. vivax, for which a continuous culture system is not yet available.
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Affiliation(s)
- Sasinee Bunyarataphan
- National Center for Genetic Engineering and Biotechnology, 113 Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120, Thailand
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Totani K, Matsuo I, Ihara Y, Ito Y. High-mannose-type glycan modifications of dihydrofolate reductase using glycan–methotrexate conjugates. Bioorg Med Chem 2006; 14:5220-9. [PMID: 16647263 DOI: 10.1016/j.bmc.2006.04.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 03/31/2006] [Accepted: 04/01/2006] [Indexed: 11/29/2022]
Abstract
Various high-mannose-type glycan modifications of dihydrofolate reductase (DHFR) were achieved by ligand-based approach using glycan-methotrexate (MTX) conjugates as tight binding glycan bearing ligands for DHFR. The resulting glycan-MTX conjugates and the corresponding artificial glycoproteins could be useful as oligosaccharide- and glycoprotein-probes to perform quantitative analysis of glycan recognizing protein such as lectins, glycosyltransferases or glycosidases. Moreover, artificial glycoproteins having two different high-mannose-type glycans were developed for the first time by a combination of two different types of glycan modification strategies.
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Affiliation(s)
- Kiichiro Totani
- RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
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Abstract
MOTIVATION Virtual screening of molecular compound libraries is a potentially powerful and inexpensive method for the discovery of novel lead compounds for drug development. The major weakness of virtual screening-the inability to consistently identify true positives (leads)-is likely due to our incomplete understanding of the chemistry involved in ligand binding and the subsequently imprecise scoring algorithms. It has been demonstrated that combining multiple scoring functions (consensus scoring) improves the enrichment of true positives. Previous efforts at consensus scoring have largely focused on empirical results, but they have yet to provide a theoretical analysis that gives insight into real features of combinations and data fusion for virtual screening. RESULTS We demonstrate that combining multiple scoring functions improves the enrichment of true positives only if (a) each of the individual scoring functions has relatively high performance and (b) the individual scoring functions are distinctive. Notably, these two prediction variables are previously established criteria for the performance of data fusion approaches using either rank or score combinations. This work, thus, establishes a potential theoretical basis for the probable success of data fusion approaches to improve yields in in silico screening experiments. Furthermore, it is similarly established that the second criterion (b) can, in at least some cases, be functionally defined as the area between the rank versus score plots generated by the two (or more) algorithms. Because rank-score plots are independent of the performance of the individual scoring function, this establishes a second theoretically defined approach to determining the likely success of combining data from different predictive algorithms. This approach is, thus, useful in practical settings in the virtual screening process when the performance of at least two individual scoring functions (such as in criterion a) can be estimated as having a high likelihood of having high performance, even if no training sets are available. We provide initial validation of this theoretical approach using data from five scoring systems with two evolutionary docking algorithms on four targets, thymidine kinase, human dihydrofolate reductase, and estrogen receptors of antagonists and agonists. Our procedure is computationally efficient, able to adapt to different situations, and scalable to a large number of compounds as well as to a greater number of combinations. Results of the experiment show a fairly significant improvement (vs single algorithms) in several measures of scoring quality, specifically "goodness-of-hit" scores, false positive rates, and "enrichment". This approach (available online at http://gemdock.life. nctu.edu.tw/dock/download.php) has practical utility for cases where the basic tools are known or believed to be generally applicable, but where specific training sets are absent.
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Affiliation(s)
- Jinn-Moon Yang
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 30050, Taiwan.
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13
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Abstract
How well do different classification methods perform in selecting the ligands of a protein target out of large compound collections not used to train the model? Support vector machines, random forest, artificial neural networks, k-nearest-neighbor classification with genetic-algorithm-optimized feature selection, trend vectors, naïve Bayesian classification, and decision tree were used to divide databases into molecules predicted to be active and those predicted to be inactive. Training and predicted activities were treated as binary. The database was generated for the ligands of five different biological targets which have been the object of intense drug discovery efforts: HIV-reverse transcriptase, COX2, dihydrofolate reductase, estrogen receptor, and thrombin. We report significant differences in the performance of the methods independent of the biological target and compound class. Different methods can have different applications; some provide particularly high enrichment, others are strong in retrieving the maximum number of actives. We also show that these methods do surprisingly well in predicting recently published ligands of a target on the basis of initial leads and that a combination of the results of different methods in certain cases can improve results compared to the most consistent method.
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Liu B, Liu M, Xin Z, Zhao H, Serby MD, Kosogof C, Nelson LTJ, Szczepankiewicz BG, Kaszubska W, Schaefer VG, Falls HD, Lin CW, Collins CA, Sham HL, Liu G. Optimization of 2,4-diaminopyrimidines as GHS-R antagonists: Side chain exploration. Bioorg Med Chem Lett 2006; 16:1864-8. [PMID: 16442284 DOI: 10.1016/j.bmcl.2006.01.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2005] [Revised: 12/27/2005] [Accepted: 01/04/2006] [Indexed: 11/23/2022]
Abstract
The synthesis and structure-activity relationships of the 4- and 6-substituents of 2,4-diaminopyrimidine-based growth hormone secretagogue receptor (GHS-R) antagonists are described. Diaminopyrimidines with 6-norbornenyl (4n) and 6-tetrahydrofuranyl (4p) substitutents were found to exhibit potent GHS-R antagonism and good selectivity (approximately 1000-fold) against dihydrofolate reductase.
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Affiliation(s)
- Bo Liu
- Metabolic Disease Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064-6098, USA
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15
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Gomez HL, Santillana SL, Vallejos CS, Velarde R, Sanchez J, Wang X, Bauer NL, Hockett RD, Chen VJ, Niyikiza C, Hanauske AR. A Phase II Trial of Pemetrexed in Advanced Breast Cancer: Clinical Response and Association with Molecular Target Expression. Clin Cancer Res 2006; 12:832-8. [PMID: 16467096 DOI: 10.1158/1078-0432.ccr-05-0295] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE This phase II trial of pemetrexed explored potential correlations between treatment outcome (antitumor activity) and molecular target expression. EXPERIMENTAL DESIGN Chemonaïve patients with advanced breast cancer received up to three cycles of pemetrexed 500 mg/m2 (10-minute i.v. infusion) on day 1 of a 21-day cycle, with folic acid and vitamin B12 supplementation. Tumors were surgically removed after the last cycle of pemetrexed as clinically indicated. Biopsies were taken at baseline, 24 hours after infusion in cycle 1, and after cycle 3. RESULTS Sixty-one women (median age, 46 years; range, 32-72 years) were treated and were evaluable for response. Objective response rate was 31%. Simple logistic regression suggested a potential relationship between mRNA expression of thymidylate synthase (TS) and pemetrexed response (P = 0.103). Based on threshold analysis, patients with "low" baseline TS (< or = 71) were more likely to respond to pemetrexed than patients with "high" baseline TS (>71). Expression of baseline dihydrofolate reductase and glycinamide ribonucleotide formyl transferase tended to be higher in responders but this association was not significant (P > 0.311). TS expression increased significantly between baseline and biopsy 2 (P = 0.004) and dropped to near baseline levels at biopsy 3. Conversely, dihydrofolate reductase and glycinamide ribonucleotide formyl transferase decreased after pemetrexed chemotherapy. CONCLUSIONS Our results suggest a potential association between "low" pretreatment TS expression levels and response to pemetrexed chemotherapy. Future trials examining expression levels of other genes important to the folate pathway and/or breast cancer may identify a more robust multigene profile that can better predict response to this novel antifolate.
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Gangjee A, Zeng Y, Ihnat M, Warnke LA, Green DW, Kisliuk RL, Lin FT. Novel 5-substituted, 2,4-diaminofuro[2,3-d]pyrimidines as multireceptor tyrosine kinase and dihydrofolate reductase inhibitors with antiangiogenic and antitumor activity. Bioorg Med Chem 2005; 13:5475-91. [PMID: 16039863 DOI: 10.1016/j.bmc.2005.04.087] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2004] [Accepted: 04/25/2005] [Indexed: 11/22/2022]
Abstract
Recent evidence suggests that combination therapy of cancer with receptor tyrosine kinase (RTK) inhibitors, which are usually cytostatic, with conventional chemotherapeutic agents, which are usually cytotoxic, provide an improved treatment option. We have designed, synthesized, and evaluated a series of novel 2,4-diamino-5-substituted furo[2,3-d]pyrimidines with RTK and dihydrofolate reductase (DHFR) inhibitory activity in single molecules, as potential cytostatic and cytotoxic agents with antitumor activity. These compounds were synthesized from 2,4-diamino-5-chloromethyl furo[2,3-d]pyrimidine and aryl methyl ketones using the Wittig reaction to afford the C-8-C-9 unsaturated analogs followed by catalytic reduction to the corresponding saturated compounds. The saturated and unsaturated C-8-C-9 bridged compounds were evaluated as inhibitors of vascular endothelial growth factor receptor (VEGFR-2, Flk, KDR), epidermal growth factor receptor, and platelet-derived growth factor receptor-beta (PDGFR-beta). Selected analogs were also evaluated as antiangiogenic agents in the chicken embryo chorioallantoic membrane (CAM) assay. The compounds were also evaluated as inhibitors of human (h) DHFR and Toxoplasma gondii (tg) DHFR. In each evaluation, a known standard compound was used as a comparison. Of the compounds evaluated, compound 32 was as potent as the standard compounds against VEGFR-2 and PDGFR-beta, showing dual inhibitory activity against RTK. This analog was also highly effective in the CAM assay. A second analog 18 also demonstrated dual VEGFR-2 and PDGFR-beta inhibitory activity as well as potent antiangiogenic activity in the CAM assay. Four additional analogs were also effective against PDGFR-beta and in the CAM assay. An unsaturated C-8-C-9 moiety was necessary for RTK inhibitory activity. Compound 32 also showed inhibitory activity against hDHFR and tgDHFR, illustrating the multitarget inhibitory potential of these analogs. The biological activity of these analogs also suggests the necessity of an unsaturated C-8-C-9 bridge for dual RTK and DHFR inhibitory activity. Compounds 18 and 32 were also evaluated in a B16 melanoma mouse model and were found to be more active as antitumor agents than methotrexate. In addition, both 18 and 32 were also active in decreasing lung metastases in a mouse model of B16 melanomas.
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Affiliation(s)
- Aleem Gangjee
- Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA 15282, USA.
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Navarro-Martínez MD, Navarro-Perán E, Cabezas-Herrera J, Ruiz-Gómez J, García-Cánovas F, Rodríguez-López JN. Antifolate activity of epigallocatechin gallate against Stenotrophomonas maltophilia. Antimicrob Agents Chemother 2005; 49:2914-20. [PMID: 15980368 PMCID: PMC1168674 DOI: 10.1128/aac.49.7.2914-2920.2005] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The catechin epigallocatechin gallate, one of the main constituents of green tea, showed strong antibiotic activity against 18 isolates of Stenotrophomonas maltophilia (MIC range, 4 to 256 microg/ml). In elucidating its mechanism of action, we have shown that epigallocatechin gallate is an efficient inhibitor of S. maltophilia dihydrofolate reductase, a strategic enzyme that is considered an attractive target for the development of antibacterial agents. The inhibition of S. maltophilia dihydrofolate reductase by this tea compound was studied and compared with the mechanism of a nonclassical antifolate compound, trimethoprim. Investigation of dihydrofolate reductase was undertaken with both a trimethoprim-susceptible S. maltophilia isolate and an isolate with a high level of resistance. The enzymes were purified using ammonium sulfate precipitation, gel filtration, and methotrexate affinity chromatography. The two isolates showed similar levels of dihydrofolate reductase expression and similar substrate kinetics. However, the dihydrofolate reductase from the trimethoprim-resistant isolate demonstrated decreased susceptibility to inhibition by trimethoprim and epigallocatechin gallate. As with other antifolates, the action of epigallocatechin gallate was synergistic with that of sulfamethoxazole, a drug that blocks folic acid metabolism in bacteria, and the inhibition of bacterial growth was attenuated by including leucovorin in the growth medium. We conclude that the mechanism of action of epigallocatechin gallate on S. maltophilia is related to its antifolate activity.
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Affiliation(s)
- María Dolores Navarro-Martínez
- Grupo de Investigación de Enzimología, Departamento de Bioquímica y Biología Molecular A, Facultad de Biología, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain
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18
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Khabnadideh S, Pez D, Musso A, Brun R, Pérez LMR, González-Pacanowska D, Gilbert IH. Design, synthesis and evaluation of 2,4-diaminoquinazolines as inhibitors of trypanosomal and leishmanial dihydrofolate reductase. Bioorg Med Chem 2005; 13:2637-49. [PMID: 15755663 DOI: 10.1016/j.bmc.2005.01.025] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Accepted: 01/14/2005] [Indexed: 11/28/2022]
Abstract
This paper describes the design, synthesis and evaluation of a series of 2,4-diaminoquinazolines as inhibitors of leishmanial and trypanosomal dihydrofolate reductase. Compounds were designed by a generating virtual library of compounds and docking them into the enzyme active site. Following their synthesis, they were found to be potent and selective inhibitors of leishmanial dihydrofolate reductase. The compounds were also found to have potent activity against Trypanosoma brucei rhodesiense, a causative organism of African trypanosomiasis and also against Trypanosoma cruzi, the causative organism of Chagas disease. There was significantly lower activity against Leishmania donovani, one of the causative organisms of leishmaniasis.
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Affiliation(s)
- Soghra Khabnadideh
- Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff, CF10 3XF, UK
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19
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da Cunha EFF, de Castro Ramalho T, Bicca de Alencastro R, Maia ER. Interactions of 5-deazapteridine derivatives with Mycobacterium tuberculosis and with human dihydrofolate reductases. J Biomol Struct Dyn 2005; 22:119-30. [PMID: 15317473 DOI: 10.1080/07391102.2004.10506988] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
There are major differences between the structures of human dihydrofolate reductase (hDHFR) and Mycobacterium tuberculosis dihydrofolate reductase (mtDHFR). These differences may allow us to design more selective mtDHFR inhibitors. In this paper we study the reactions of six different compounds derived from 5-deazapteridine with human and bacterial enzymes. Results suggest that the addition of hydrophobic groups to the aminophenyl ring would increase mtDHFR-inhibitor affinity and selectivity.
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Affiliation(s)
- Elaine F F da Cunha
- Instituto de Quimica da Universidade Federal do Rio de Janeiro--UFRJ, Departamento de Quimica Organica, Centro de Tecnologia-Bl A-Sala 609, Ilha do Fundao, Rio de Janeiro, CEP 21949-900 - RJ--Brazil.
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20
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Abstract
We present the results of a comprehensive study in which we explored how the docking procedure affects the performance of a virtual screening approach. We used four docking engines and applied 10 scoring functions to the top-ranked docking solutions of seeded databases against six target proteins. The scores of the experimental poses were placed within the total set to assess whether the scoring function required an accurate pose to provide the appropriate rank for the seeded compounds. This method allows a direct comparison of library ranking efficacy. Our results indicate that the LigandFit/Ligscore1 and LigandFit/GOLD docking/scoring combinations, and to a lesser degree FlexX/FlexX, Glide/Ligscore1, DOCK/PMF (Tripos implementation), LigandFit1/Ligscore2 and LigandFit/PMF (Tripos implementation) were able to retrieve the highest number of actives at a 10% fraction of the database when all targets were looked upon collectively. We also show that the scoring functions rank the observed binding modes higher than the inaccurate poses provided that the experimental poses are available. This finding stresses the discriminatory ability of the scoring algorithms, when better poses are available, and suggests that the number of false positives can be lowered with conformers closer to bioactive ones.
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Affiliation(s)
- Maria Kontoyianni
- Johnson & Johnson Pharmaceutical Research & Development, L.L.C., Computer Assisted Drug Discovery, Welsh and McKean Roads, P.O. Box 776, Spring House, Pennsylvania 19477, USA.
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21
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Gangjee A, Zeng Y, McGuire JJ, Mehraein F, Kisliuk RL. Synthesis of Classical, Three-Carbon-Bridged 5-Substituted Furo[2,3-d]pyrimidine and 6-Substituted Pyrrolo[2,3-d]pyrimidine Analogues as Antifolates. J Med Chem 2004; 47:6893-901. [PMID: 15615538 DOI: 10.1021/jm040123k] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Bridge homologation of the previously reported classical two-carbon-bridged antifolates, a 5-substituted 2,4-diaminofuro[2,3-d]pyrimidine (1) [which is a 6-regioisomer of LY231514 (Alimta)] and a 6-subsituted 2-amino-4-oxopyrrolo[2,3-d]pyrimidine, afforded the three-carbon-bridged antifolates analogues 4 and 5, with enhanced inhibitory activity against tumor cells in culture (EC(50) values in the 10(-8)-10(-7) M range or less). These two analogues were synthesized via a 10-step synthetic sequence starting from methyl 4-bromobenzoate (14), which was elaborated to the alpha-chloromethyl ketone (8) followed by condensation with 2,6-diamino-pyrimidin-4-one (7) to afford the substituted furo[2,3-d]pyrimidine 9 and the pyrrolo[2,3-d]pyrimidine 10. Subsequent coupling of each regioisomer with diethyl-l-glutamate followed by saponification afforded 4 and 5. The biological results indicate that elongation of the C8-C9 bridge of the classical 5-substituted 2,4-diaminofuro[2,3-d]pyrimidine and 6-substituted 2-amino-4-oxopyrrolo[2,3-d]pyrimidine are highly conducive to antitumor activity in vitro, despite a lack of increase in inhibitory activity against the target enzymes. This supports our original hypothesis that truncation of the B-ring of a highly potent 6-6 ring system to a 6-5 ring system can be compensated by bridge homologation to restore the overall length of the molecule.
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Affiliation(s)
- Aleem Gangjee
- Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA 15282, USA.
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22
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Mayer S, Daigle DM, Brown ED, Khatri J, Organ MG. An Expedient and Facile One-Step Synthesis of a Biguanide Library by Microwave Irradiation Coupled with Simple Product Filtration. Inhibitors of Dihydrofolate Reductase. ACTA ACUST UNITED AC 2004; 6:776-82. [PMID: 15360213 DOI: 10.1021/cc049953+] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It has been demonstrated previously by us that guanide-containing compounds (1 and 2) can inhibit significantly dihydrofolate reductase (DHFR). In this report, we have produced an array of alkyl- and aryl-based biguanide compounds using microwave irradiation. Further, we have demonstrated the use of TMSCl for the first time as an excellent and practical catalyst for the formation of alkyl and aryl biguanides. Using these methods, we prepared a 60-compound collection, of which one compound (21g) showed approximately one-half of the inhibitory activity of the parent compound 2.
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Affiliation(s)
- Stanislas Mayer
- Department of Chemistry, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3
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23
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Ahmed A, Bararia D, Vinayak S, Yameen M, Biswas S, Dev V, Kumar A, Ansari MA, Sharma YD. Plasmodium falciparum isolates in India exhibit a progressive increase in mutations associated with sulfadoxine-pyrimethamine resistance. Antimicrob Agents Chemother 2004; 48:879-89. [PMID: 14982779 PMCID: PMC353157 DOI: 10.1128/aac.48.3.879-889.2004] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The combination of sulfadoxine-pyrimethamine (SP) is used as a second line of therapy for the treatment of uncomplicated chloroquine-resistant Plasmodium falciparum malaria. Resistance to SP arises due to certain point mutations in the genes for the dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) enzymes of the parasite. We have analyzed these mutations in 312 field isolates of P. falciparum collected from different parts of India to assess the effects of drug pressure. The rate of mutation in the gene for DHFR was found to be higher than that in the gene for DHPS, although the latter had mutations in more alleles. There was a temporal rise in the number of isolates with double dhfr mutations and single dhps mutations, resulting in an increased total number of mutations in the loci for DHFR and DHPS combined over a 5-year period. During these 5 years, the number of isolates with drug-sensitive genotypes decreased and the number of isolates with drug-resistant genotypes (double DHFR mutations and a single DHPS mutation) increased significantly. The number of isolates with the triple mutations in each of the genes for the two enzymes (for a total of six mutations), however, remained very low, coinciding with the very low rate of SP treatment failure in the country. There was a regional bias in the mutation rate, as isolates from the northeastern region (the state of Assam) showed higher rates of mutation and more complex genotypes than isolates from the other regions. It was concluded that even though SP is prescribed as a second line of treatment in India, the mutations associated with SP resistance continue to be progressively increasing.
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Affiliation(s)
- Anwar Ahmed
- Department of Biotechnology, All India Institute of Medical Sciences, New Delhi 110029. Malaria Research Centre, 22 Sham Nath Marg, New Delhi 110054, India
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24
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Chiu TL, So SS. Development of neural network QSPR models for Hansch substituent constants. 2. Applications in QSAR studies of HIV-1 reverse transcriptase and dihydrofolate reductase inhibitors. ACTA ACUST UNITED AC 2004; 44:154-60. [PMID: 14741022 DOI: 10.1021/ci030294i] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this paper, the applications of a Hansch substituent constant predictor(1) to Quantitative Structure-Activity Relationships (QSAR) studies of E. coli dihydrofolate reductase (DHFR) inhibitors 2,4-diamino-5-(substituted-benzyl)pyrimidines as well as HIV-1 reverse transcriptase (RT) inhibitors 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) derivatives are demonstrated. Both data sets contain functional groups for which the substituent constants (pi, MR, F and R) could not be found in standard substituent constant tables. The substituent constant predictor allowed us to derive predicted pi, MR, F and R values for all substituents in both data sets, thus enabling the generation of easily interpretable QSAR models of comparable or better predictivity than previous models.
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Affiliation(s)
- Ting-Lan Chiu
- Roche Research Center, Hoffmann-La Roche Inc, Nutley, New Jersey 07110, USA
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25
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Hall AJ, Achilli L, Manesiotis P, Quaglia M, De Lorenzi E, Sellergren B. A Substructure Approach toward Polymeric Receptors Targeting Dihydrofolate Reductase Inhibitors. 2. Molecularly Imprinted Polymers against Z-l-Glutamic Acid Showing Affinity for Larger Molecules. J Org Chem 2003; 68:9132-5. [PMID: 14604396 DOI: 10.1021/jo034588e] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The preparation of a molecularly imprinted polymer against N-Z-L-glutamic acid using a novel bis-urea functional monomer is described. The polymer exhibits affinity for the template over N-Z-protected aspartic acid and glycine and, further, is capable of binding larger molecules, e.g., the anti-cancer drug methotrexate, containing the glutamate substructure.
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Affiliation(s)
- Andrew J Hall
- Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg Universität, Duesbergweg 10-14, D-55099, Mainz, Germany.
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26
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Mayer-Kuckuk P, Doubrovin M, Gusani NJ, Gade T, Balatoni J, Akhurst T, Finn R, Fong Y, Koutcher JA, Larson S, Blasberg R, Tjuvajev JG, Bertino JR, Banerjee D. Imaging of dihydrofolate reductase fusion gene expression in xenografts of human liver metastases of colorectal cancer in living rats. Eur J Nucl Med Mol Imaging 2003; 30:1281-91. [PMID: 12664136 DOI: 10.1007/s00259-003-1143-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Radionuclide imaging has been demonstrated to be feasible to monitor transgene expression in vivo. We hypothesized that a potential application of this technique is to non-invasively detect in deep tissue, such as cancer cells metastatic to the liver, a specific molecular response following systemic drug treatment. Utilizing human colon adenocarcinoma cells derived from a patient's liver lesion we first developed a nude rat xenograft model for colorectal cancer metastatic to the liver. Expression of a dihydrofolate reductase-herpes simplex virus 1 thymidine kinase fusion (DHFR-HSV1 TK) transgene in the hepatic tumors was monitored in individual animals using the tracer [(124)I]2'-fluoro-2'-deoxy-5-iodouracil-beta- d-arabinofuranoside (FIAU) and a small animal micro positron emission tomograph (microPET), while groups of rats were imaged using the tracer [(131)I]FIAU and a clinical gamma camera. Growth of the human metastatic colorectal cancer cells in the rat liver was detected using magnetic resonance imaging and confirmed by surgical inspection. Single as well as multiple lesions of different sizes and sites were observed in the liver of the animals. Next, using a subset of rats bearing hepatic tumors, which were retrovirally bulk transduced to express the DHFR-HSV1 TK transgene, we imaged the fusion protein expression in the hepatic tumor of living rats using the tracer [(124)I]FIAU and a microPET. The observed deep tissue signals were highly specific for the tumors expressing the DHFR-HSV1 TK fusion protein compared with parental untransduced tumors and other tissues as determined by gamma counting of tissue samples. A subsequent study used the tracer [(131)I]FIAU and a gamma camera to monitor two groups of transduced hepatic tumor-bearing rats. Prior to imaging, one group was treated with trimetrexate to exploit DHFR-mediated upregulation of the fusion gene product. Imaging in the living animal as well as subsequent gamma counting of tissue samples showed increased signal and tracer accumulation, respectively, as compared to the group not treated with the antifolate. It is concluded that the two examined nucleotide imaging methods are feasible techniques for monitoring of DHFR-HSV TK fusion protein expression in hepatic colorectal tumor tissue in living animals.
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Affiliation(s)
- Philipp Mayer-Kuckuk
- Molecular Pharmacology and Therapeutics Program, Memorial Sloan-Kettering Cancer Center, New York, NY, USA
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27
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Moufarij MA, Phillips DR, Cullinane C. Gemcitabine potentiates cisplatin cytotoxicity and inhibits repair of cisplatin-DNA damage in ovarian cancer cell lines. Mol Pharmacol 2003; 63:862-9. [PMID: 12644587 DOI: 10.1124/mol.63.4.862] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Synergistic cytotoxicity between cisplatin and the nucleoside analog gemcitabine was observed in a panel of cisplatin-sensitive (2008, A2780) and -resistant (2008/C13*5.25, A2780/CP70) human ovarian cell lines. Previous studies have suggested a role for DNA repair in the mechanism of synergy between the two drugs. We therefore further investigated the hypothesis that the synergistic cytotoxicity between gemcitabine and cisplatin in these cell lines may be caused by gemcitabine-mediated inhibition of cisplatin intrastrand adduct (IA) and interstand cross-link (ICL) repair. The effect of gemcitabine on the accumulation and repair of cisplatin IA and ICL in each cell line was then measured directly using gene-specific quantitative polymerase chain reaction and denaturation/renaturation techniques, respectively. Pretreatment of 2008 cells with 1 microM gemcitabine for 2 h before exposure to cisplatin for 7 h enhanced the accumulation of cisplatin IA and ICL by 50 and 40%, respectively (P < 0.05), above that induced by cisplatin alone. To investigate the possibility that the increased accumulation of cisplatin lesions was caused by inhibition of removal of cisplatin damage, 2008 cells were incubated with 200 microM cisplatin for 5 h in the presence and absence of gemcitabine and then a further 8 h in the absence of cisplatin. Only 57% IA were removed in the combination treated cells compared with 74% in cisplatin control cells. Similarly, repair of cisplatin ICL was inhibited in the gemcitabine-treated cells compared with the cells treated with cisplatin only (60 versus 72%). These findings demonstrate a direct inhibitory effect of gemcitabine on the repair of cisplatin IA and ICL and suggest a mechanistic basis for the cytotoxic synergy between the two drugs.
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Affiliation(s)
- Mazin A Moufarij
- Trescowthick Research Laboratories, Peter MacCallum Cancer Institute, Melbourne, Victoria, Australia
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28
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Sardarian A, Douglas KT, Read M, Sims PF, Hyde JE, Chitnumsub P, Sirawaraporn R, Sirawaraporn W. Pyrimethamine analogs as strong inhibitors of double and quadruple mutants of dihydrofolate reductase in human malaria parasites. Org Biomol Chem 2003; 1:960-4. [PMID: 12929634 DOI: 10.1039/b211636g] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pyrimethamine acts against malarial parasites by selectively inhibiting their dihydrofolate reductase-thymidylate synthase. Resistance to pyrimethamine in Plasmodium falciparum is due to point mutations in the DHFR domain, initially at residue 108 (S108N), with additional mutations imparting much greater resistance. Our previous work, the development of a simple rational drug design strategy to overcome such resistance, used suitable meta-substituents in the pyrimethamine framework to avoid the unfavorable steric clash with mutant side chains at position 108. Interestingly, the meta-chloro analog of pyrimethamine not only overcame the resistance due to S108N, but also that contributed by the more remote mutation, C59R. The present work improves on this by means of other meta-substituents. Against wild type DHFR, double mutant types A16V + S108T and C59R + S108T, and the highly pyrimethamine/cycloguanil-resistant quadruple-mutant form N51I + C59R + S108N + I164L, pyrimethamine itself gave Ki values of 1.5, 2.4, 72.3 and 859 nM, respectively. The meta-substituted analogs, especially the meta-bromo analog, were much more powerful inhibitors of these DHFRs, including the quadruple-mutant form (meta-bromo analog, Ki 5.1 nM). For comparison, the dihydropyrazine antifolate, WR99210, gave Ki values of 0.9, 3.2, 0.8 and 0.9 nM, respectively. Ki values were also measured against recombinant human DHFR, as were their activities against the growth of Plasmodium falciparum cultures bearing the double mutations (FCB and K1 strains) and quadruple mutation (V1/S) and the wild type (3D7). The meta-analogs were highly active against all of these, with the meta-bromo again being the strongest, having an IC50 of 37 nM against V1/S, compared to > 5000 nM for pyrimethamine itself and 1.1 nM for WR99210.
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Affiliation(s)
- Alireza Sardarian
- School of Pharmacy and Pharmaceutical Sciences, University of Manchester, Manchester, UK M13 9PL
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29
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Mure K, Uddin AN, Lopez LC, Styblo M, Rossman TG. Arsenite induces delayed mutagenesis and transformation in human osteosarcoma cells at extremely low concentrations. Environ Mol Mutagen 2003; 41:322-331. [PMID: 12802802 DOI: 10.1002/em.10164] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Arsenite is a human multisite carcinogen, but its mechanism of action is not known. We recently found that extremely low concentrations (</=0.1 microM) of arsenite transform human osteosarcoma TE85 (HOS) cells to anchorage-independence. In contrast to other carcinogens which transform these cells within days of exposure, almost 8 weeks of arsenite exposure are required for transformation. We decided to reexamine the question of arsenite mutagenicity using chronic exposure in a spontaneous mutagenesis assay we previously developed. Arsenite was able to cause a delayed increase in mutagenesis at extremely low concentrations (</=0.1 microM) in a dose-dependent manner. The increase in mutant frequency occurred after almost 20 generations of growth in arsenite. Transformation required more than 30 generations of continuous exposure. We also found that arsenite induced gene amplification of the dihydrofolate reductase (DHFR) gene in a dose-dependent manner. Since HOS cells are able to methylate arsenite at a very low rate, it was possible that active metabolites such as monomethylarsonous acid (MMA(III)) contributed to the delayed mutagenesis and transformation in these cells. However, when the assay was repeated with MMA(III), we found no significant increase in mutagenesis or transformation, suggesting that arsenite-induced delayed mutagenesis and transformation are not caused by arsenite's metabolites, but by arsenite itself. Our results suggest that long-term exposure to low concentrations of arsenite may affect signaling pathways that result in a progressive genomic instability.
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Affiliation(s)
- Kanae Mure
- New York University School of Medicine, Nelson Institute of Environmental Medicine, Tuxedo, New York 10987, USA
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30
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Abstract
Thymidylate synthase (TS) catalyses the de novo synthesis of deoxythymidylate and is a key rate-limiting enzyme of DNA synthesis. The primary site of action of the classic antifolate methotrexate is direct inhibition of dihydrofolate reductase, but it also inhibits TS indirectly by diminishing levels of the TS cosubstrate 5,10-methylenetetrahydrofolate. Polyglutamated metabolites of methotrexate also directly bind and inhibit TS. The prototype fluoropyrimidine fluorouracil is metabolised to an irreversible inhibitor of TS and is the standard chemotherapy for gastrointestinal carcinomas. It is also frequently used in combination with other anticancer drugs against breast cancer and head and neck cancers. The clinical efficacy of fluorouracil is routinely increased by concomitant administration of the biomodulating compound leucovorin (folinic acid). Both the success and limitations of these early drugs led to a search for new, more efficacious TS inhibitors active against a broader range of neoplasms. Raltitrexed (ZD1694, Tomudex) is an antifolate TS inhibitor developed over the last decade that is similarly effective, yet better tolerated, than fluorouracil against colorectal cancer. Additional antifolate and fluoropyrimidine-based TS inhibitors continue to be developed. Many of these experimental drugs have been designed to exploit or thwart selective metabolism in neoplasms, including specific mechanisms of resistance. As the curative potential of relatively non-selective antiproliferative drugs like TS inhibitors is limited against most neoplasms, the future role of TS inhibitors will likely continue to be adjunctive in surgically resectable tumours and palliative in combination with other agents for non-resectable disease. Although TS inhibitors will eventually be supplanted by yet to be discovered agents targeting more tumour-specific cellular signalling pathways, they will probably remain important for the above uses for some time. Future advances in the effective use of TS inhibitors may be forthcoming in the form of improved dosing, fewer untoward effects and increased tumour selectivity with novel fluorouracil prodrug formulations. Furthermore, there is emerging evidence that some novel antifolate TS inhibitors are active against a broader range of neoplams, including lung carcinomas and mesothelioma, compared to classical TS inhibitors. Other possible advances to come include effective biomodulation of antifolate TS inhibitors with nucleoside transport inhibitors and individualised patient therapy based on tumour gene expression and resistance patterns (pharmacogenetics).
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Affiliation(s)
- Norman L Lehman
- Department of Pathology, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, USA.
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31
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Shuper A, Stark B, Kornreich L, Cohen IJ, Avrahami G, Yaniv I. Methotrexate-related neurotoxicity in the treatment of childhood acute lymphoblastic leukemia. Isr Med Assoc J 2002; 4:1050-3. [PMID: 12489505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
The addition of methotrexate to treatment protocols in children with acute lymphoblastic leukemia has been found beneficial in preventing central nervous system relapse. However, MTX itself may be associated with neurologic morbidities, the most significant of which is leukoencephalopathy. The present study describes the clinical spectrum of leukoencephalopathy, which ranges from a subclinical disease manifested only radiologically to a progressive, devastating encephalopathy. The interaction of MTX with other components of the treatment protocol is discussed, as is the effect of leucovorin. A summary is presented of the metabolic pathways that may be involved in the development of MTX toxicity. Researchers are still seeking a biochemical marker to aid in the determination of the amount of MTX that may be safely administered.
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Affiliation(s)
- Avinoam Shuper
- Department of Pediatric Oncology-Hematology, Schneider Children's Medical Center of Israel, Petah Tiqva, Israel.
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32
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Chowdhury SF, Guerrero RH, Brun R, Ruiz-Perez LM, Pacanowska DG, Gilbert IH. Synthesis and testing of 5-benzyl-2,4-diaminopyrimidines as potential inhibitors of leishmanial and trypanosomal dihydrofolate reductase. J Enzyme Inhib Med Chem 2002; 17:293-302. [PMID: 12683746 DOI: 10.1080/1475636021000059083] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Dihydrofolate reductase is a drug target that has not been thoroughly investigated in leishmania and trypanosomes. Work has previously shown that 5-benzyl-2,4-diaminopyrimidines are selective inhibitors of the leishmanial and trypanosome enzymes. Modelling predicted that alkyl/aryl substitution on the 6-position of the pyrimidine ring should increase enzyme activity of 5-benzyl-2,4-diaminopyrimidines as inhibitors of leishmanial and trypanosomal dihydrofolate reductase. Various compounds were prepared and evaluated against both the recombinant enzymes and the intact organisms. The presence of a substituent had a small or negative effect on activity against the enzyme or intact parasites compared to unsubstituted compounds.
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Affiliation(s)
- Shafinaz F Chowdhury
- Welsh School of Pharmacy, Cardiff University, Redwood Building, King Edward VII Avenue, Cardiff, CF10 3XF, UK
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Chan DCM, Laughton CA, Queener SF, Stevens MFG. Structural studies on bioactive compounds. Part 36: design, synthesis and biological evaluation of pyrimethamine-based antifolates against Pneumocystis carinii. Bioorg Med Chem 2002; 10:3001-10. [PMID: 12110323 DOI: 10.1016/s0968-0896(02)00128-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
As part of a research effort to improve the quality of current chemotherapy of Pneumocystis carinii pneumonia, we report a structure-based design project to optimise activity, species selectivity and pharmaceutical properties of the triazenyl-pyrimethamine TAB (4) (IC(50)=0.17 microM; rat liver DHFR IC(50)/P. carinii DHFR IC(50)=114). This has led us to design, synthesise and evaluate four new series of pyrimethamine derivatives bearing triazole, triazolium, triazinium and amino moieties at the 3'-position of the p-chlorophenyl ring. Such stabilised 'triazene' derivatives address the potentially compromised pharmaceutical profile of TAB and the 3'-amine substituted agents afford conformationally flexible substitutes. The benzylamino-pyrimethamine derivative (24a) (IC(50)=0.12 microM, rat liver DHFR IC(50)/P. carinii DHFR IC(50): 5.26) was the most potent and the only P. carinii-selective antifolate of the new series.
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Affiliation(s)
- David C M Chan
- Cancer Research Laboratories, School of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, UK
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Abstract
Three commercially available pharmacophore generation programs, Catalyst/HipHop, DISCO and GASP, were compared on their ability to generate known pharmacophores deduced from protein-ligand complexes extracted from the Protein Data Bank. Five different protein families were included Thrombin, Cyclin Dependent Kinase 2, Dihydrofolate Reductase, HIV Reverse Transcriptase and Thermolysin. Target pharmacophores were defined through visual analysis of the data sets. The pharmacophore models produced were evaluated qualitatively through visual inspection and according to their ability to generate the target pharmacophores. Our results show that GASP and Catalyst outperformed DISCO at reproducing the five target pharmacophores.
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Affiliation(s)
- Yogendra Patel
- Krebs Institute for Biomolecular Research and Department of Information Studies, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom
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35
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Bertino JR. Is there life after methotrexate? Cancer Invest 2002; 20:593-4. [PMID: 12094553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
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36
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Banerjee D, Mayer-Kuckuk P, Capiaux G, Budak-Alpdogan T, Gorlick R, Bertino JR. Novel aspects of resistance to drugs targeted to dihydrofolate reductase and thymidylate synthase. Biochim Biophys Acta 2002; 1587:164-73. [PMID: 12084458 DOI: 10.1016/s0925-4439(02)00079-0] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Drug resistance is often a limiting factor in successful chemotherapy. Our laboratory has been interested in studying mechanisms of resistance to drugs that are targeted to the thymidylate biosynthesis pathway especially those that target thymidylate synthase (TS) and dihydrofolate reductase (DHFR). We have used leukemia as a model system to study resistance to methotrexate (MTX) and colorectal cancer as the model system to study 5-fluorouracil (5-FU) resistance. In leukemias, we and others have shown that transport, efflux, polyglutamylation and hydrolase activities are major determinants of MTX resistance. We have further reported that some leukemic cells have an increase in DHFR gene copy number possibly contributing to the resistant phenotype. Recently, we have begun to study in detail the molecular mechanisms that govern translational regulation of DHFR in response to MTX as an additional resistance mechanism. Studies thus far involving colorectal tumors obtained from patients have focused predominantly on the predictive value of levels of TS expression and p53 mutations in determining response to 5-FU. Although the predictive value of these two measures appears to be significant, given the variety of resistance to 5-FU observed in cell lines, it is not likely that these are the only measures predictive of response or responsible for acquired resistance to this drug. The enzyme uridine-cytidine monophosphate kinase (UMPK) is an essential and rate-limiting enzyme in 5-FU activation while dihydropyrimidine dehydrogenase (DPD) is a catabolic enzyme that inactivates 5-FU. Alterations in UMPK and DPD may therefore explain failure of 5-FU response in the absence of alterations in TS or p53. Transcription factors that regulate TS may also influence drug sensitivity. We have found that mRNA levels of the E2F family of transcription factors correlates with TS message levels and are higher in lung metastases than in liver metastases of colorectal cancers. Moreover, gene copy number of the E2F-1 gene appears to be increased in a significant number of samples obtained from metastases of colorectal cancer. We have also generated mutants of both DHFR and TS that confer resistance to MTX as well as 5-FU by random as well as site-directed mutagenesis. These mutants used alone or as fusion cDNAs of the mutants have proven to be useful in transplant studies where transfer of these mutant cDNAs to bone marrow cells have been shown to confer drug resistance to recipients. The fusion cDNAs of DHFR such as the DHFR-herpes simplex virus type 1 thymidine kinase (HSVTK) are also useful for regulation of gene expression in vivo using MTX as the small molecule regulator that can be monitored by positron emission tomography (PET) scanning or by optical imaging using a fusion construct such as DHFR-EGFP.
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Affiliation(s)
- Debabrata Banerjee
- Program of Molecular Pharmacology and Experimental Therapeutics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.
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Espinoza H, Ellertson C, García S, Schiavon R, Langer A. [Medical methods for pregnancy termination. A review of literature and its potential role in Mexico and Latin America]. GAC MED MEX 2002; 138:347-56. [PMID: 12200879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023] Open
Abstract
In this document, we review the relevant aspects of the different medical methods of abortion. We describe the principal medical regimens currently used in North America, Europe, and a growing number of developing countries. We also describe specific treatment regimens (which usually involve a combination of two drugs), physiological methods of action, potential side effects and complications, method requirements, including follow-up visits, any existing contraindication, and acceptability of these methods among patients. Finally, we comment on the potential role of medical abortion in Mexico and throughout Latin America.
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Affiliation(s)
- Henry Espinoza
- Population Council, Oficina Regional para América Latina y el Caribe, Escondida 110, Col. Villa Coyoacán, 04000 México, D. F.
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Riebeseel K, Biedermann E, Löser R, Breiter N, Hanselmann R, Mülhaupt R, Unger C, Kratz F. Polyethylene glycol conjugates of methotrexate varying in their molecular weight from MW 750 to MW 40000: synthesis, characterization, and structure-activity relationships in vitro and in vivo. Bioconjug Chem 2002; 13:773-85. [PMID: 12121133 DOI: 10.1021/bc010098m] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Poly(ethylene glycol)s (PEGs) are potential drug carriers for improving the therapeutic index of anticancer agents. In this work, the anticancer drug methotrexate (MTX) was activated with N,N'-dicyclohexylcarbodiimide (DCC) and coupled to amino group bearing PEGs of MW 750, 2000, 5000, 10 000, 20,000, and 40,000. First, the activation process of MTX with DCC in the presence and absence of N-hydroxysuccinimide was analyzed through HPLC. Preincubation of methotrexate with DCC alone at 0 degrees C proved to be favorable with respect to the amount of activated species and the formation of byproducts. MTX-PEG conjugates were synthesized according to this procedure, isolated through size-exclusion chromatography, and characterized through analytical HPLC, MALDI-TOF spectrometry, and gel permeation chromatography. In a cell-free assay, all of the drug polymer conjugates inhibited the target enzyme of MTX, dihydrofolate reductase (DHFR), to a similar extent, but were not as active as free MTX. Additionally, incubation of the MTX-PEG40000 conjugate for 6 days at 37 degrees C in phosphate buffered saline (pH 7.4), in cell-conditioned medium, or in human serum revealed no significant release of methotrexate. These results, taken together, indicate that release of MTX from polymer conjugates is not necessary for an effective interaction with the active site of dihydrofolate reductase. Evaluation of the in vitro cytotoxicity of the MTX-PEG conjugates in two adherent and three suspension human tumor cell lines revealed that the IC(50) values of the tested compounds increased with the size of the drug-polymer conjugates. The most effective compound tested in these assays was the free drug MTX itself (IC(50) value ranging from approximately 0.01 to 0.05 microM), while the IC(50) values of the polymer conjugates were higher (IC(50) value for MTX-PEG750, 2000 and 5000: approximately 0.6-3 microM; for MTX-PEG10000 and 20000: approximately 2-7 microM; and for MTX-PEG40000: > 6 microM). Subsequently, MTX-PEG5000, MTX-PEG20000, and MTX-PEG40000 were evaluated in a human mesothelioma MSTO-211H xenograft model, and their antitumor effects were compared with free methotrexate and the albumin conjugate MTX-HSA, a conjugate that is currently in phase II clinical trials. In contrast to the in vitro results, the high molecular weight MTX-PEG conjugates exhibited the highest in vivo antitumor activity: At a dose of 40 and 80 mg/kg MTX-PEG5000 was less active than MTX at its optimal dose of 100 mg/kg; MTX-PEG20000 at a dose of 40 mg/kg showed antitumor efficacy comparable to MTX, but MTX-PEG40000 at a dose of 20 mg/kg was superior to MTX and demonstrated antitumor activity of the same order as MTX-HSA (20 mg/kg).
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Affiliation(s)
- Katja Riebeseel
- Tumor Biology Center, Department of Medical Oncology, Clinical Research, Breisacher Strasse 117, 79106 Freiburg, Germany
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Landavazo DG, Fogel GB, Fogel DB. Quantitative structure-activity relationships by evolved neural networks for the inhibition of dihydrofolate reductase by pyrimidines. Biosystems 2002; 65:37-47. [PMID: 11888662 DOI: 10.1016/s0303-2647(01)00192-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Evolutionary computation provides a useful method for training neural networks in the face of multiple local optima. This paper begins with a description of methods for quantitative structure activity relationships (QSAR). An overview of artificial neural networks for pattern recognition problems such as QSAR is presented and extended with the description of how evolutionary computation can be used to evolve neural networks. Experiments are conducted to examine QSAR for the inhibition of dihydrofolate reductase by pyrimidines using evolved neural networks. Results indicate the utility of evolutionary algorithms and neural networks for the predictive task at hand. Furthermore, results that are comparable or perhaps better than those published previously were obtained using only a small fraction of the previously required degrees of freedom.
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Affiliation(s)
- Dana G Landavazo
- Natural Selection Inc., 3333 N. Torrey Pines Ct., Suite 200, 92037, La Jolla, CA 92037, USA
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Urakawa K, Mihara M, Takagi N, Kawamura A, Akamatsu KI, Takeda Y. Polyglutamation of a novel antifolate, MX-68, is not necessary for its anti-arthritic effect. Eur J Pharmacol 2002; 435:237-44. [PMID: 11821032 DOI: 10.1016/s0014-2999(01)01553-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
N-[[4-[(2,4-diaminopteridin-6-yl)methyl]-3,4-dihydro-2H-1,4-benzothiazin-7-yl]-carbonyl]-L-homoglutamic acid (MX-68), a derivative of methotrexate, was chemically designed to resist polyglutamation and to have a high affinity for dihydrofolate reductase, in an attempt to reduce the side effects of methotrexate. We confirmed that MX-68 did not undergo polyglutamation and investigated the pharmacological activities of MX-68 compared with methotrexate. (1) In vitro: MX-68 inhibited the activity of dihydrofolate reductase to the same degree as methotrexate-tetraglutamate. MX-68 treatment produced a similar anti-proliferative effect to that of methotrexate. However, the intracellular concentration of MX-68 was much lower than the sum of the levels of methotrexate and its polyglutamate, and the effects of MX-68 disappeared when it was removed from the culture medium. (2) In vivo: Oral administration of MX-68 suppressed the development of collagen-induced arthritis in mice and adjuvant-induced arthritis in rats, in a similar fashion to that of methotrexate. These results indicate that polyglutamation is not essential for the anti-arthritic effect of antifolates.
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Affiliation(s)
- Kazumi Urakawa
- Fuji Gotemba Research Laboratories, Chugai Pharmaceutical Co., Ltd., 1-135, Komakado, Gotemba, 412-8513, Shizuoka, Japan.
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41
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Au WY, Ma ESK, Kwong YL. Intravenous pentamidine induced megaloblastic anaemia. Haematologica 2002; 87:ECR06. [PMID: 11801480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023] Open
Affiliation(s)
- Wing Y Au
- University Department of Medicine, Professorial Block, Queen Mary Hospital, Pokfulam Road, Hong Kong, ROC.
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42
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Biswas S. Plasmodium falciparum dihydrofolate reductase Val-16 and Thr-108 mutation associated with in vivo resistance to antifolate drug: a case study. Indian J Malariol 2001; 38:76-83. [PMID: 12125519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
Abstract
Due to increasing trend in chloroquine resistance, the antifolate (sulpha-pyrimethamine combination) drugs are gaining more importance in the treatment of uncomplicated falciparum malaria. The efficacy of sulpha-pyrimethamine combinations in the treatment is compromised by the development of resistance in parasite. The occurrence of mutations at active sites in Plasmodium falciparum gene sequences coding for dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) confer resistance to pyrimethamine and sulphadoxine. This study presents the characterization of a P. falciparum sample from a patient who did not respond to standard doses of a pyrimethamine/sulpha regimen. Although parasitaemia fell rapidly, the infection had not resolved six days later as because the response to treatment selected resistant sub-population. The in vitro drug sensitivity assays demonstrated resistance to pyrimethamine, sulphadoxine and cycloguanil; while polymerase chain reaction (PCR) and restriction digest based methods indicated that at known drug resistant loci the isolate had a genotype of DHFR Val-16 and Thr-108 previously only associated with cycloguanil resistance. As per the published reports this type of paired mutations in natural isolates are rare. It is of considerable interest to carry out studies on alleles on alleles of this gene in relation to resistance at epidemiological level.
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Affiliation(s)
- S Biswas
- Malaria Research Centre, 22-Sham Nath Marg, Delhi-110 054, India
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Santos-Filho OA, Mishra RK, Hopfinger AJ. Free energy force field (FEFF) 3D-QSAR analysis of a set of Plasmodium falciparum dihydrofolate reductase inhibitors. J Comput Aided Mol Des 2001; 15:787-810. [PMID: 11776291 DOI: 10.1023/a:1013199108020] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Free energy force field (FEFF) 3D-QSAR analysis was used to construct ligand-receptor binding models for a set of 18 structurally diverse antifolates including pyrimethamine, cycloguanil, methotrexate, aminopterin and trimethoprim, and 13 pyrrolo[2,3-d]pyrimidines. The molecular target ('receptor') used was a 3D-homology model of a specific mutant type of Plasmodium falciparum (Pf) dihydrofolate reductase (DHFR). The dependent variable of the 3D-QSAR models is the IC50 inhibition constant for the specific mutant type of PfDHFR. The independent variables of the 3D-QSAR models (the descriptors) are scaled energy terms of a modified first-generation AMBER force field combined with a hydration shell aqueous solvation model and a collection of 2D-QSAR descriptors often used in QSAR studies. Multiple temperature molecular dynamics simulation (MDS) and the genetic function approximation (GFA) were employed using partial least square (PLS) and multidimensional linear regressions as the fitting functions to develop FEFF 3D-QSAR models for the binding process. The significant FEFF energy terms in the best 3D-QSAR models include energy contributions of the direct ligand-receptor interaction. Some changes in conformational energy terms of the ligand due to binding to the enzyme are also found to be important descriptors. The FEFF 3D-QSAR models indicate some structural features perhaps relevant to the mechanism of resistance of the PfDHFR to current antimalarials. The FEFF 3D-QSAR models are also compared to receptor-independent (RI) 4D-QSAR models developed in an earlier study and subsequently refined using recently developed generalized alignment rules.
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Affiliation(s)
- O A Santos-Filho
- Laboratory of Molecular Modeling and Design, University of Illinois at Chicago, College of Pharmacy, 60612-7231, USA
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44
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Abstract
While assays of many antifolate inhibitors for dihydrofolate reductase (DHFR) have been performed using rat DHFR as a target, neither the sequence nor the structure of rat DHFR is known. Here, we report the isolation of the rat DHFR gene through screening of a rat liver cDNA library. The rat liver DHFR gene has an open reading frame of 561 bp encoding a protein of 187 amino acids. Comparisons of the rat enzyme with those from other species indicate a high level of conservation at the primary sequence level and more so for the amino acid residues comprising the active site of the enzyme. Expression of the rat DHFR gene in bacteria produced a recombinant protein with high enzymatic activity. The recombinant protein also paralleled the human enzyme with respect to the inhibition by most of the antifolates tested with PT652 and PT653 showing a reversal in their patterns. Our results indicated that rat DHFR can be used as a model to study antifolate compounds as potential drug candidates. However, variations between rat and human DHFR enzymes, coupled with unique features in the inhibitors, could lead to the observed differences in enzyme sensitivity and selectivity.
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Affiliation(s)
- Y Wang
- Structural Biology Department, Hauptman Woodward Medical Research Institute, Buffalo, New York 14203, USA
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45
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Chowdhury SF, Di Lucrezia R, Guerrero RH, Brun R, Goodman J, Ruiz-Perez LM, Pacanowska DG, Gilbert IH. Novel inhibitors of Leishmanial dihydrofolate reductase. Bioorg Med Chem Lett 2001; 11:977-80. [PMID: 11327604 DOI: 10.1016/s0960-894x(01)00089-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The program DOCK3.5 was used to search the Cambridge Structural Database for novel inhibitors of Leishmanial dihydrofolate reductase. A number of compounds were obtained and screened against the enzyme and against the intact parasite Leishmania donovani and the related organisms Trypanosoma brucei and Trypanosoma cruzi. The compounds screened showed weak activity in both the enzyme assays and the in vitro assays.
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46
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Abstract
It is anticipated that the sequencing of Plasmodium falciparum genome will soon be completed. Rodent models of malaria infection and stable transformation systems provide powerful means of using this information to study gene function in vivo. To date, gene targeting has only been developed for one rodent malaria species, Plasmodium berghei. Another rodent species, Plasmodium yoelii, however, is favored to study the mechanisms of protective immunity to the pre-erythrocytic stages of infection and vaccine development. In addition, it offers the opportunity to investigate unique aspects of pathogenesis of blood stage infection. Here, we report on the stable transfection and gene targeting of P. yoelii. Purified late blood stage schizonts were used as targets for electroporation with a plasmid that contains a pyrimethamine-resistant form of the P. berghei dihydrofolate reductase-thymidylate synthase (Pbdhfr-ts) fused to green fluorescent protein (gfp) gene. After drug selection, fluorescent parasites contained intact, non-rearranged plasmids that remain stable under drug-pressure. In addition, we used another dhfr-ts/gfp based plasmid to disrupt the P. yoelii trap (thrombospondin-related anonymous protein) locus by site-specific integration. The phenotype of P. yoelii TRAP knockout was identical to that previously reported for the P. berghei TRAP knockout. In the absence of TRAP, the erythrocytic cycle, gametocyte and oocyst development of the mutant parasites were indistinguishable from wild type (WT). Although the sporozoites appeared morphologically normal, they failed to glide and to invade the salivary glands of mosquitoes.
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Affiliation(s)
- M M Mota
- Michael Heidelberger Division, Department of Pathology (MSB131), New York University Medical Center, 550 First Avenue, New York, NY 10016, USA.
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47
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Abstract
N-[4-[[2,4-diamino-6-pteridinyl)methyl]amino]bicyclo[2.2.2]octane-1-carbonyl]-L-glutamic acid (1) was synthesized and tested for antifolate activity. N-(4-Aminobicyclo[2.2.2]octane-1-carbonyl-L-glutamic acid dimethyl ester (6), the side chain precursor to subject compound 1, was synthesized readily via reported bicyclo[2.2.2]octane-1,4-dicarboxylic acid monoethyl ester (2). The side chain precursor 6 was alkylated by 6-(bromomethyl)-2,4-pteridinediamine (7). Subsequent ester hydrolysis then afforded 1. Antifolate and antitumor evaluation of 1 verses L1210 dihydrofolate reductase (DHFR) and three tumor cell lines (L1210, S180, and HL60) showed it to be ineffective. Although compound 1 was very similar to aminopterin structurally, the bicyclo[2.2.2]octane ring system in place of the phenyl ring in the p-aminobenzoate moiety effectively negates the stoichiometric binding displayed by many classical DHFR inhibitors bearing appropriate aromatic ring systems in the side chain.
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Affiliation(s)
- R C Reynolds
- Organic Chemistry Department, Southern Research Institute, Birmingham, AL 35255, USA.
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48
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Iqbal MP, Burney IA, Sultana F, Mehboobali N. Induction of white cell proliferation due to haematopoietic growth factors is associated with an increase in multiple forms of dihydrofolate reductase in non-neutropenic cancer patients. J PAK MED ASSOC 2001; 51:68-71. [PMID: 11321874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Abstract
OBJECTIVE Granulocyte-colony stimulating factor (G-CSF) and granulocyte macrophage-colony stimulating factor (GM-CSF) are frequently used in cancer patients to overcome the granulocytopenic effects of chemotherapy, and also to mobilize the stem cells. The mobilized stem cells are collected from the peripheral blood and used for transplantation following high doses of chemotherapy. However, the molecular mechanism by which these colony stimulating factors (CSFs) bring about proliferation of myeloid precursor cells is not clearly known. Dihydrofolate reductase (DHFR), which has an established role in DNA synthesis, could be a link between administration of CSF and stem cell proliferation. The purpose of this study was to investigate whether CSFs induce white cell proliferation by producing multiple forms of DHFR. METHODS Twelve patients with non-haematological malignancies were treated with either G-CSF or GM-CSF to mobilize stem cells. Nine healthy subjects were treated with placebo as controls. Blood samples were obtained before and after stimulation with CSFs or placebo. White blood cells were separated and concentrations of both active DHFR and immunoreactive nonfunctional form of DHFR were determined in their cytoplasm using methotrexate-binding assay and enzyme-linked immunosorbent assay, respectively. Total leucocytes count (TLC) was also monitored before and after stimulation with CSFs or placebo. RESULTS There was a significant (P < 0.05) increase in concentration of immunoreactive nonfunctional form of DHFR and TLC following stimulation with CSFs. There was an increase in concentration of active DHFR as well, however, this did not reach statistical significance. In the placebo-treated subjects, no significant increase in active DHFR, immunoreactive nonfunctional form of enzyme or TLC was observed. However, it was noticed that the base-line values of active DHFR and immunoreactive nonfunctional form of enzyme in leucocytes of cancer patients were higher than the base-line values in leukocytes of normal healthy subjects. CONCLUSION Our data suggest that colony stimulating factors induce white cell proliferation by increasing levels of multiple forms of DHFR.
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Affiliation(s)
- M P Iqbal
- Department of Biochemistry, Aga Khan University, Karachi
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Smith VF, Matthews CR. Testing the role of chain connectivity on the stability and structure of dihydrofolate reductase from E. coli: fragment complementation and circular permutation reveal stable, alternatively folded forms. Protein Sci 2001; 10:116-28. [PMID: 11266600 PMCID: PMC2249853 DOI: 10.1110/ps.26601] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2000] [Revised: 10/26/2000] [Accepted: 10/26/2000] [Indexed: 10/14/2022]
Abstract
The effects of chain cleavage and circular permutation on the structure, stability, and activity of dihydrofolate reductase (DHFR) from Escherichia coli were investigated by various spectroscopic and biochemical methods. Cleavage of the backbone after position 86 resulted in two fragments, (1--86) and (87--159) each of which are poorly structured and enzymatically inactive. When combined in a 1 : 1 molar ratio, however, the fragments formed a high-affinity (K(a) = 2.6 x 10(7) M(-1)) complex that displays a weakly cooperative urea-induced unfolding transition at micromolar concentrations. The retention of about 15% of the enzymatic activity of full-length DHFR is surprising, considering that the secondary structure in the complex is substantially reduced from its wild-type counterpart. In contrast, a circularly permuted form with its N-terminus at position 86 has similar overall stability to full-length DHFR, about 50% of its activity, substantial secondary structure, altered side-chain packing in the adenosine binding domain, and unfolds via an equilibrium intermediate not observed in the wild-type protein. After addition of ligand or the tight-binding inhibitor methotrexate, both the fragment complex and the circular permutant adopt more native-like secondary and tertiary structures. These results show that changes in the backbone connectivity can produce alternatively folded forms and highlight the importance of protein-ligand interactions in stabilizing the active site architecture of DHFR.
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Affiliation(s)
- V F Smith
- Department of Chemistry, Life Sciences Consortium and Center for Biological Structure and Function, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Santos-Filho OA, Hopfinger AJ. A search for sources of drug resistance by the 4D-QSAR analysis of a set of antimalarial dihydrofolate reductase inhibitors. J Comput Aided Mol Des 2001; 15:1-12. [PMID: 11217916 DOI: 10.1023/a:1011152818340] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A set of 18 structurally diverse antifolates including pyrimethamine, cycloguanil, methotrexate, aminopterin and trimethoprim, and 13 pyrrolo[2,3-d pyrimidines were studied using four-dimensional quantitative structure-activity relationship (4D-QSAR) analysis. The corresponding biological activities of these compounds include IC50 inhibition constants for both the wild type, and a specific mutant type of Plasmodium falciparum dihydrofolate reductase (DHFR). Two thousand conformations of each analog were sampled to generate a conformational ensemble profile (CEP) from a molecular dynamics simulation (MDS) of 100,000 conformer trajectory states. Each sampled conformation was placed in a 1 A cubic grid cell lattice for each of five trial alignments. The frequency of occupation of each grid cell was computed for each of six types of pharmacophore groups of atoms of each compound. These grid cell occupancy descriptors (GCODs) were then used as a descriptor pool to construct 4D-QSAR models. Models for inhibition of both the 'wild' type and the mutant enzyme were generated which provide detailed spatial pharmacophore requirements for inhibition in terms of atom types and their corresponding relative locations in space. The 4D-QSAR models indicate some structural features perhaps relevant to the mechanism of resistance of the Plasmodium falciparum DHFR to current antimalarials. One feature identified is a slightly different binding alignment of the ligands to the mutant form of the enzyme as compared to the wild type.
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Affiliation(s)
- O A Santos-Filho
- Laboratory of Molecular Modeling and Design, University of Illinois at Chicago, College of Pharmacy, 80612-7231, USA
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