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Shaikh AY, Björkling F, Zabicka D, Tomczak M, Urbas M, Domraceva I, Kreicberga A, Franzyk H. Structure-activity study of oncocin: On-resin guanidinylation and incorporation of homoarginine, 4-hydroxyproline or 4,4-difluoroproline residues. Bioorg Chem 2023; 141:106876. [PMID: 37797458 DOI: 10.1016/j.bioorg.2023.106876] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [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: 07/26/2023] [Revised: 09/14/2023] [Accepted: 09/18/2023] [Indexed: 10/07/2023]
Abstract
Antimicrobial peptides (AMPs) often display guanidinium functionalities, and hence robust synthetic procedures are needed to facilitate access to analogues with unnatural homologues of arginine (Arg = R). Initially, a resin-bound Arg/Pro-rich fluoren-9-yl-methyloxycarbonyl-protected fragment (Fmoc-RPRPPR) of the AMP oncocin (i.e., VDKPPYLPRPRPPRRIYNR-NH2) was employed in a comparative on-resin assessment of commercial guanidinylation reagents head-to-head with the recently studied bis-Boc-protected triazole-based reagent, 1H-triazole-1-[N,N'-bis(tert-butoxycarbonyl)]-carboxamidine, which was synthesized by a chromatography-free procedure. This reagent was found to enable quantitative conversion in solid-phase peptide synthesis (SPPS) of peptides displaying homoarginine (Har) residues and/or an N-terminal guanidinium group. SPPS was used to obtain analogues of the 18-mer oncocin with single as well as multiple Arg → Har modifications. In addition, the effect of replacement of proline (Pro) residues in oncocin was explored by incorporating single or multiple trans-4-hydroxy-l-proline (Hyp) or 4,4-difluoro-l-proline (Dfp) residues, which both affected hydrophobicity. The resulting peptide library was tested against both Gram-negative and Gram-positive bacteria. Analysis of the minimal inhibitory concentrations (MICs) showed that analogues, displaying modifications at positions 4, 5 and 12 (originally Pro residues), had retained or slightly improved antimicrobial activity. Next, an oncocin analogue with two stabilizing l-Arg → d-Arg replacements in the C-terminal part was further modified by triple-replacement of Pro by either Dfp or Hyp in positions 4, 5, and 12. The resulting analogue displaying three Pro → Dfp modifications proved to possess the best activity profile: MICs of 1-2 µg/mL against E. coli and Klebsiella pneumoniae, less than 1% hemolysis at 800 µg/mL, and an IC50 above 1280 µg/mL in HepG2 cells. Thus, incorporation of bis-fluorinated Pro residues appears to constitute a novel tool in structure-activity studies aimed at optimization of Pro-rich AMPs.
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Affiliation(s)
- Ashif Y Shaikh
- Center for Peptide-Based Antibiotics, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 162, DK-2100, Denmark; Department of Chemistry, Khalifa University, Abu Dhabi 127788, United Arab Emirates
| | - Fredrik Björkling
- Center for Peptide-Based Antibiotics, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 162, DK-2100, Denmark
| | - Dorota Zabicka
- Department of Epidemiology and Clinical Microbiology, National Medicines Institute, ul. Chełmska 30/34, 00-725 Warsaw, Poland
| | - Magdalena Tomczak
- Department of Epidemiology and Clinical Microbiology, National Medicines Institute, ul. Chełmska 30/34, 00-725 Warsaw, Poland
| | - Malgorzata Urbas
- Department of Epidemiology and Clinical Microbiology, National Medicines Institute, ul. Chełmska 30/34, 00-725 Warsaw, Poland
| | - Ilona Domraceva
- Latvian Institute of Organic Synthesis, Aizkraukles 21, 1006 Riga, Latvia
| | - Agrita Kreicberga
- Latvian Institute of Organic Synthesis, Aizkraukles 21, 1006 Riga, Latvia
| | - Henrik Franzyk
- Center for Peptide-Based Antibiotics, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 162, DK-2100, Denmark.
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Luck VL, Richards DP, Shaikh AY, Franzyk H, Mellor IR. The Effects of Structural Alterations in the Polyamine and Amino Acid Moieties of Philanthotoxins on Nicotinic Acetylcholine Receptor Inhibition in the Locust, Schistocerca gregaria. Molecules 2021; 26:molecules26227007. [PMID: 34834099 PMCID: PMC8622278 DOI: 10.3390/molecules26227007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 11/16/2021] [Accepted: 11/17/2021] [Indexed: 11/16/2022] Open
Abstract
Alterations in the polyamine and amino acid (tyrosine) moieties of philanthotoxin-343 (PhTX-343) were investigated for their effects on the antagonism of nicotinic acetylcholine receptors (nAChRs) isolated from the locust (Schistocerca gregaria) mushroom body. Through whole-cell patch-clamp recordings, the philanthotoxin analogues in this study were shown to cause inhibition of the inward current when co-applied with acetylcholine (ACh). PhTX-343 (IC50 = 0.80 μM at -75 mV) antagonised locust nAChRs in a use-dependent manner, suggesting that it acts as an open-channel blocker. The analogue in which both the secondary amine functionalities were replaced with methylene groups (i.e., PhTX-12) was ~6-fold more potent (IC50 (half-maximal inhibitory concentration) = 0.13 μM at -75 mV) than PhTX-343. The analogue containing cyclohexylalanine as a substitute for the tyrosine moiety of PhTX-343 (i.e., Cha-PhTX-343) was also more potent (IC50 = 0.44 μM at -75 mV). A combination of both alterations to PhTX-343 generated the most potent analogue, i.e., Cha-PhTX-12 (IC50 = 1.71 nM at -75 mV). Modulation by PhTX-343 and Cha-PhTX-343 fell into two distinct groups, indicating the presence of two pharmacologically distinct nAChR groups in the locust mushroom body. In the first group, all concentrations of PhTX-343 and Cha-PhTX-343 inhibited responses to ACh. In the second group, application of PhTX-343 or Cha-PhTX-343 at concentrations ≤100 nM caused potentiation, while concentrations ≥ 1 μM inhibited responses to ACh. Cha-PhTX-12 may have potential to be developed into insecticidal compounds with a novel mode of action.
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Affiliation(s)
- Victoria L. Luck
- School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK; (V.L.L.); (D.P.R.)
| | - David P. Richards
- School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK; (V.L.L.); (D.P.R.)
| | - Ashif Y. Shaikh
- Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, 2100 Copenhagen, Denmark; (A.Y.S.); (H.F.)
| | - Henrik Franzyk
- Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 162, 2100 Copenhagen, Denmark; (A.Y.S.); (H.F.)
| | - Ian R. Mellor
- School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK; (V.L.L.); (D.P.R.)
- Correspondence: ; Tel.: +44-1159-513257
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Shaikh AY, Björkling F, Nielsen PE, Franzyk H. Optimized Synthesis of Fmoc/Boc‐Protected PNA Monomers and their Assembly into PNA Oligomers. European J Org Chem 2021. [DOI: 10.1002/ejoc.202100278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ashif Y. Shaikh
- Center for Peptide-based Antibiotics, Department of Drug Design and Pharmacology Faculty of Heath and Medical Sciences University of Copenhagen Jagtvej 162 2100 Copenhagen Denmark
| | - Fredrik Björkling
- Center for Peptide-based Antibiotics, Department of Drug Design and Pharmacology Faculty of Heath and Medical Sciences University of Copenhagen Jagtvej 162 2100 Copenhagen Denmark
| | - Peter E. Nielsen
- Center for Peptide-based Antibiotics, Department of Cellular and Molecular Medicine, The Panum Institute, Faculty of Heath and Medical Sciences University of Copenhagen Blegdamsvej 3 2200 Copenhagen Denmark
| | - Henrik Franzyk
- Center for Peptide-based Antibiotics, Department of Drug Design and Pharmacology Faculty of Heath and Medical Sciences University of Copenhagen Jagtvej 162 2100 Copenhagen Denmark
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Hsieh WC, Shaikh AY, Perera JDR, Thadke SA, Ly DH. Synthesis of ( R)- and ( S)-Fmoc-Protected Diethylene Glycol Gamma PNA Monomers with High Optical Purity. J Org Chem 2019; 84:1276-1287. [PMID: 30608165 DOI: 10.1021/acs.joc.8b02714] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [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: 11/30/2022]
Abstract
A robust synthetic route has been developed for preparing optically pure, Fmoc-protected diethylene glycol-containing ( R)- and ( S)-γPNA monomers. The strategy involves the application of 9-(4-bromophenyl)-9-fluorenyl as a temporary, safety-catch protecting group for the suppression of epimerization in the O-alkylation and reductive amination steps. The optical purities of the final monomers were determined to be greater than 99.5% ee, as assessed by 19F-NMR and HPLC. The new synthetic methodology is well-suited for large-scale monomer production, with most synthetic steps providing excellent chemical yields without the need for chromatographic purification other than a simple workup and precipitation.
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Affiliation(s)
- Wei-Che Hsieh
- Institute for Biomolecular Design and Discovery (IBD) and Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
| | - Ashif Y Shaikh
- Institute for Biomolecular Design and Discovery (IBD) and Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
| | - J Dinithi R Perera
- Institute for Biomolecular Design and Discovery (IBD) and Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
| | - Shivaji A Thadke
- Institute for Biomolecular Design and Discovery (IBD) and Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
| | - Danith H Ly
- Institute for Biomolecular Design and Discovery (IBD) and Department of Chemistry , Carnegie Mellon University , 4400 Fifth Avenue , Pittsburgh , Pennsylvania 15213 , United States
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Thadke SA, Perera JDR, Hridya VM, Bhatt K, Shaikh AY, Hsieh WC, Chen M, Gayathri C, Gil RR, Rule GS, Mukherjee A, Thornton CA, Ly DH. Design of Bivalent Nucleic Acid Ligands for Recognition of RNA-Repeated Expansion Associated with Huntington's Disease. Biochemistry 2018; 57:2094-2108. [PMID: 29562132 PMCID: PMC6091552 DOI: 10.1021/acs.biochem.8b00062] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [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] [Indexed: 01/19/2023]
Abstract
We report the development of a new class of nucleic acid ligands that is comprised of Janus bases and the MPγPNA backbone and is capable of binding rCAG repeats in a sequence-specific and selective manner via, inference, bivalent H-bonding interactions. Individually, the interactions between ligands and RNA are weak and transient. However, upon the installation of a C-terminal thioester and an N-terminal cystine and the reduction of disulfide bond, they undergo template-directed native chemical ligation to form concatenated oligomeric products that bind tightly to the RNA template. In the absence of an RNA target, they self-deactivate by undergoing an intramolecular reaction to form cyclic products, rendering them inactive for further binding. The work has implications for the design of ultrashort nucleic acid ligands for targeting rCAG-repeat expansion associated with Huntington's disease and a number of other related neuromuscular and neurodegenerative disorders.
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Affiliation(s)
- Shivaji A. Thadke
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Institute for Biomolecular Design and Discovery (IBD), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Center for Nucleic Acids Science and Technology (CNAST), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - J. Dinithi R. Perera
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Institute for Biomolecular Design and Discovery (IBD), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Center for Nucleic Acids Science and Technology (CNAST), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - V. M. Hridya
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Maharashtra 411008, India
| | - Kirti Bhatt
- Department of Neurology, Box 645, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, New York 14642, United States
| | - Ashif Y. Shaikh
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Institute for Biomolecular Design and Discovery (IBD), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Center for Nucleic Acids Science and Technology (CNAST), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Wei-Che Hsieh
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Institute for Biomolecular Design and Discovery (IBD), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Center for Nucleic Acids Science and Technology (CNAST), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Mengshen Chen
- Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Chakicherla Gayathri
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Roberto R. Gil
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Gordon S. Rule
- Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
| | - Arnab Mukherjee
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Maharashtra 411008, India
| | - Charles A. Thornton
- Department of Neurology, Box 645, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, New York 14642, United States
| | - Danith H. Ly
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Institute for Biomolecular Design and Discovery (IBD), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
- Center for Nucleic Acids Science and Technology (CNAST), Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States
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Shaikh AY, Das S, Pati D, Dhaware V, Sen Gupta S, Hotha S. Cationic charged helical glycopolypeptide using ring opening polymerization of 6-deoxy-6-azido-glyco-N-carboxyanhydride. Biomacromolecules 2014; 15:3679-86. [PMID: 25122513 DOI: 10.1021/bm5009537] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Glycopolypeptides with a defined secondary structure are of significance in understanding biological phenomena. Synthetic glycopolypeptides, or polypeptides featuring pendant carbohydrate moieties, have been of particular interest in the field of tissue engineering and drug delivery. In this work, we have synthesized charged water-soluble glycopolypeptides that adopt a helical conformation in water. This was carried out by the synthesis of a glyco-N-carboxyanhydride (glyco-NCA) containing an azide group at the sixth position of the carbohydrate ring. Subsequently, the NCA was polymerized to obtain azide-containing glycopolypeptides having good control over molecular weight and polydispersity index (PDI) in high yields. We were also able to control the incorporation of the azide group by synthesizing random co-glycopolypeptide containing 6-deoxy-6-azido and regular 6-OAc functionalized glucose. This azide functionality allows for the easy attachment of a bioactive group, which could potentially enhance the biological activity of the glycopolypeptide. We were able to obtain water-soluble charged glycopolypeptides by both reducing the azide groups into amines and using CuAAC with propargylamine. These charged glycopolypeptides were shown to have a helical conformation in water. Preliminary studies showed that these charged glycopolypeptides showed good biocompatibility and were efficiently taken up by HepG2 cells.
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Affiliation(s)
- Ashif Y Shaikh
- CSIR-National Chemical Laboratory , Dr. Homi Bhabha Road, Pune-411 008, India
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Abstract
The synthesis of the amphiphilic homoglycopolypeptide was carried out by a combination of NCA polymerization and click chemistry to yield a well-defined polypeptide having an amphiphilic carbohydrate on its side chain. The amphiphilicity of the carbohydrate was achieved by incorporation of an alkyl chain at the C-6 position of the carbohydrate thus also rendering the homoglycopolypeptide amphiphilic. The homoglycopolypeptide formed multimicellar aggregates in water above a critical concentration of 0.9 μM due to phase separation. The multimicellar aggregates were characterized by DLS, TEM, and AFM. It is proposed that hydrophobic interactions of the aliphatic chains at the 6-position of the sugar moieties drives the assembly of these rod-like homoglycopolypeptide into large spherical aggregates. These multimicellar aggregates encapsulate both hydrophilic as well as hydrophobic dye as was confirmed by confocal microscopy. Finally, amphiphilic random polypeptides containing 10% and 20% α-d-mannose in addition to glucose containing a hydrophobic alkyl chain at its 6 position were synthesized by our methodology, and these polymers were also found to assemble into spherical nanostructures. The spherical assemblies of amphiphilic random glycopolypeptides containing 10% and 20% mannose were found to be surface bioactive and were found to interact with the lectin Con-A.
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Affiliation(s)
- Vinita Dhaware
- Chemical Engineering Division, National Chemical Laboratory, Pune, India
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Pati D, Shaikh AY, Das S, Nareddy PK, Swamy MJ, Hotha S, Gupta SS. Controlled Synthesis of O-Glycopolypeptide Polymers and Their Molecular Recognition by Lectins. Biomacromolecules 2012; 13:1287-95. [DOI: 10.1021/bm201813s] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Debasis Pati
- CReST, Chemical
Engineering Division, National Chemical Laboratory (CSIR), Dr. Homi Bhabha Road, Pune-411 008,
India
| | - Ashif Y. Shaikh
- CReST, Chemical
Engineering Division, National Chemical Laboratory (CSIR), Dr. Homi Bhabha Road, Pune-411 008,
India
| | - Soumen Das
- CReST, Chemical
Engineering Division, National Chemical Laboratory (CSIR), Dr. Homi Bhabha Road, Pune-411 008,
India
| | | | - Musti J Swamy
- School of Chemistry, University of Hyderabad, Hyderabad-500046,
India
| | - Srinivas Hotha
- Department
of Chemistry, Indian Institute of Science Education and Research, Pune-411 021, India
| | - Sayam Sen Gupta
- CReST, Chemical
Engineering Division, National Chemical Laboratory (CSIR), Dr. Homi Bhabha Road, Pune-411 008,
India
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Shumway D, Corbin K, Salgia R, Hoffman P, Villaflor V, Malik RM, Haraf DJ, Vigneswaren WT, Shaikh AY, Connell PP, Ferguson MK, Salama JK. Pathologic response rates following definitive dose image-guided chemoradiotherapy and resection for locally advanced non-small cell lung cancer. Lung Cancer 2011; 74:446-50. [PMID: 21676484 DOI: 10.1016/j.lungcan.2011.05.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 04/29/2011] [Accepted: 05/01/2011] [Indexed: 10/18/2022]
Abstract
INTRODUCTION Treatment of technically operable, medically fit locoregionally advanced non-small cell lung cancer (NSCLC) patients is a controversial therapeutic challenge. Our group routinely uses a trimodality approach. Recent advances in radiotherapy allow for improved tumor targeting and daily patient positioning. We hypothesized that these technologies would improve pathologic response rates. We analyzed consecutively treated stage IIIA/IIIB NSCLC patients undergoing chemoradiotherapy before major lung resection, with particular attention paid to the impact of advanced technologies. METHODS Locoregionally advanced NSCLC patients (N2) staged in a multidisciplinary forum with mediastinoscopy were planned to receive platinum-based chemotherapy and 60Gy and major lung resection. Four-dimensional CT (4DCT) and image-guided radiotherapy (IGRT) were used as available. Survival endpoints were estimated using the Kaplan-Meier method and compared using the log-rank test. Multivariate analysis was performed using Cox proportional hazards models. RESULTS We identified 53 patients from 2/1999 to 2/2010. Median RT dose was 59Gy. 68% underwent lobectomy. Forty-three patients were downstaged pathologically (81%), 38 experienced mediastinal sterilization (72%), and 21 (40%) had complete pathologic response (pCR). 1 and 2 year OS were 85.5% and 61.6%. Superior OS and DFS were associated with nodal downstaging and mediastinal sterilization (pN0). Treatment with IGRT/4DCT in 10 patients resulted in high rates of nodal downstaging (100% vs 77%, p=0.0452), mediastinal sterilization (90% vs 67%, p=0.0769), and pCR (60% vs 35%, p=0.0728). CONCLUSIONS In selected patients, definitive dose CRT followed by major lung resection results in promising DFS and OS. The use of advanced radiotherapy techniques (4DCT and IGRT) appears to result in promising pathologic response rates.
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Affiliation(s)
- D Shumway
- Pritzker School of Medicine, University of Chicago, Chicago, IL, USA
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Shaikh AY, Sureshkumar G, Pati D, Gupta SS, Hotha S. Facile synthesis of unusual glycosyl carbamates and amino acid glycosides from propargyl 1,2-orthoesters as glycosyl donors. Org Biomol Chem 2011; 9:5951-9. [DOI: 10.1039/c1ob05056g] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Pati D, Shaikh AY, Hotha S, Gupta SS. Synthesis of glycopolypeptides by the ring opening polymerization of O-glycosylated-α-amino acid N-carboxyanhydride (NCA). Polym Chem 2011. [DOI: 10.1039/c0py00412j] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Tiwari DK, Shaikh AY, Pavase LS, Gumaste VK, Deshmukh ARA. Stereoselective synthesis of 3-alkylidene/alkylazetidin-2-ones from azetidin-2,3-diones. Tetrahedron 2007. [DOI: 10.1016/j.tet.2006.12.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
Stroke research has progressed in leaps and bounds in the past decades. A driving force is the increasing availability of new research tools in this field (eg, animal stroke models). Animal stroke models have been extensively applied to advance our understanding of the mechanisms of ischemic brain injury and to develop novel therapeutic strategies for reducing brain damage after a stroke. Animal stroke models have been useful in characterizing the molecular cascades of injury processes. These "injury pathways" are also the targets of therapeutic interventions. The major achievements made in the past 2 decades applying animal stroke models include 1) the identification of the mediator role of excitotoxin and oxygen free radicals in ischemic brain injury; 2) the confirmation of apoptosis as a major mechanism of ischemic cell death; 3) the characterization of postischemic gene expression; 4) the delineation of postischemic inflammatory reaction; 5) the application of transgenic mice to confirm the roles of purported mediators in ischemic brain injury; 6) development of novel magnetic resonance imaging sequences for early noninvasive detection of ischemic brain lesions; and, 7) the development of novel therapeutic strategies based on preclinical findings derived from animal stroke models.
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Affiliation(s)
- S H Ahmed
- Department of Neurology, Box 8111, Washington University School of Medicine, 660 S. Euclid Ave. St. Louis, MO 63110, USA.
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Martin LJ, Price AC, Kaiser A, Shaikh AY, Liu Z. Mechanisms for neuronal degeneration in amyotrophic lateral sclerosis and in models of motor neuron death (Review). Int J Mol Med 2000; 5:3-13. [PMID: 10601567 DOI: 10.3892/ijmm.5.1.3] [Citation(s) in RCA: 29] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS), also referred to as motor neurone disease, is a fatal neurological disease that is characterized clinically by progressive muscle weakness, muscle atrophy, and eventual paralysis. The neuropathology of ALS is primary degeneration of upper (motor cortical) and lower (brainstem and spinal) motor neurons. The amyotrophy refers to the neurogenic atrophy of affected muscle groups, and the lateral sclerosis refers to the hardening of the lateral white matter funiculus in spinal cord (corresponding to degeneration of the corticospinal tract) found at autopsy. Because the mechanisms for the motor neuron degeneration in ALS are not understood, this disease has no precisely known causes and no effective treatments. Very recent studies have identified that the degeneration of motor neurons in ALS is a form of apoptotic cell death that may occur by an abnormal programmed cell death (PCD) mechanism. In order to treat ALS effectively, we need to understand the mechanisms for motor neuron apoptosis more completely. Future studies need to further identify the signals for PCD activation in neurons as they relate to the pathogenesis of ALS and to clarify the molecular pathways leading to motor neuron apoptosis in animal and cell culture model systems. These studies should lead to a better understanding of motor neuron death and to the design of new therapeutic experiments critical for the future treatment of ALS.
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Affiliation(s)
- L J Martin
- Johns Hopkins University School of Medicine, Department of Pathology, 558 Ross Building, Baltimore, MD 21205-2196, USA
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Abstract
Hyperoxia leads to excessive formation of reactive oxygen species (ROS). ROS cause damage to many cellular components, including DNA. Exposure of bovine cerebral endothelial cells to 95 or 100% oxygen resulted in an increase in DNA fragmentation, the appearance of DNA ladders, and cell death with morphological features suggestive of apoptosis. Melatonin, an antioxidant, reduced hyperoxia-induced DNA fragmentation and cell death in a dose-dependent manner. Results from the present study support the contention that ROS play a major role in DNA damage and apoptotic death. Melatonin is an effective agent in reducing ROS-mediated DNA fragmentation and death in bovine cerebral endothelial cells.
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Affiliation(s)
- A Y Shaikh
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, USA
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