RESUMO
BACKGROUND: Head and neck cancer (HNC) incidence is on the rise, often diagnosed at late stage and associated with poor prognoses. Risk prediction tools have a potential role in prevention and early detection. METHODS: The IARC-ARCAGE European case-control study was used as the model development dataset. A clinical HNC risk prediction model using behavioral and demographic predictors was developed via multivariable logistic regression analyses. The model was then externally validated in the UK Biobank cohort. Model performance was tested using discrimination and calibration metrics. RESULTS: 1926 HNC cases and 2043 controls were used for the development of the model. The development dataset model including sociodemographic, smoking, and alcohol variables had moderate discrimination, with an area under curve (AUC) value of 0.75 (95% CI, 0.74-0.77); the calibration slope (0.75) and tests were suggestive of good calibration. 384 616 UK Biobank participants (with 1177 HNC cases) were available for external validation of the model. Upon external validation, the model had an AUC of 0.62 (95% CI, 0.61-0.64). CONCLUSION: We developed and externally validated a HNC risk prediction model using the ARCAGE and UK Biobank studies, respectively. This model had moderate performance in the development population and acceptable performance in the validation dataset. Demographics and risk behaviors are strong predictors of HNC, and this model may be a helpful tool in primary dental care settings to promote prevention and determine recall intervals for dental examination. Future addition of HPV serology or genetic factors could further enhance individual risk prediction.
Assuntos
Neoplasias de Cabeça e Pescoço , Humanos , Masculino , Neoplasias de Cabeça e Pescoço/epidemiologia , Feminino , Pessoa de Meia-Idade , Medição de Risco , Estudos de Casos e Controles , Idoso , Adulto , Reino Unido/epidemiologia , Modelos Logísticos , Fatores de Risco , Europa (Continente)/epidemiologiaRESUMO
Background: Cancer risk assessment models are used to support prevention and early detection. However, few models have been developed for head and neck cancer (HNC). Methods: A rapid review of Embase and MEDLINE identified n = 3045 articles. Following dual screening, n = 14 studies were included. Quality appraisal using the PROBAST (risk of bias) instrument was conducted, and a narrative synthesis was performed to identify the best performing models in terms of risk factors and designs. Results: Six of the 14 models were assessed as "high" quality. Of these, three had high predictive performance achieving area under curve values over 0.8 (0.87-0.89). The common features of these models were their inclusion of predictors carefully tailored to the target population/anatomical subsite and development with external validation. Conclusions: Some existing models do possess the potential to identify and stratify those at risk of HNC but there is scope for improvement.
RESUMO
4,4-Difluoro-4-bora-3a,4a-diaza-s-indacenes (F-BODIPYs) are deprotected through removal of the -BF2 moiety upon treatment with methylboronic acid. The tolerance of various substitution patterns about the dipyrrinato core is demonstrated via the deprotection of thirteen F-BODIPYs and an F-aza-BODIPY. Work-up with aq. HBr affords the desired dipyrin HBr salt in quantitative yield without need for purification.
RESUMO
2-Functionalised pyrroles exhibit considerable synthetic utility. Herein, the synthesis and reactivity of 2-thionoester (-C(S)OR) pyrroles is reported. 2-Thionoester pyrroles were synthesised using a Knorr-type approach from aliphatic starting materials. 2-Thionoester pyrroles were reduced to the corresponding 2-formyl pyrroles, or the deuterated formyl variant, in one step using RANEY® nickel, thereby removing the need for the much-utilised hydrolysis/decarboxylation/formylation steps that are typically required to convert Knorr-type 2-carboxylate pyrroles into 2-formyl pyrroles. 2-Thionoester pyrroles proved tolerant of typical functional group interconversions for which the parent 2-carboxylate pyrroles have become known.
RESUMO
Cross-coupling reactions catalyzed by transition metals are among the most influential in modern synthetic chemistry. The vast majority of transition-metal-catalyzed cross-couplings rely on a catalytic cycle involving alternating oxidation and reduction of the metal center and are generally limited to forging just one type of new bond per reaction (e.g., the biaryl linkage formed during a Suzuki cross-coupling). This work presents an Isohypsic-Redox Sequence (IRS) that uses one metal to effect two catalytic cycles, thereby generating multiple new types of bonds from a single catalyst source. We show that the IRS strategy is amenable to several widely used transformations including the Suzuki-Miyaura coupling, Buchwald-Hartwig amination, and Wacker oxidation. Furthermore, each of these reactions generates value-added heterocycles with significant sp3 -C (3-dimensional) content. Our results provide a general framework for generating complex products by using a single metal to fulfill multiple roles. By uniting different combinations of reactions in the isohypsic and redox phases of the process, this type of catalytic multiple bond-forming platform has the potential for wide applicability in the efficient synthesis of functional organic molecules.
RESUMO
Background Proton beam therapy (PBT) is available in many western and Asian countries, but there is no clinical, gantry-based PBT facility in Canada. Methods A cost analysis was conducted from the Alberta Ministry of Health perspective with a 15-year horizon. Estimated costs were: PBT unit, facility development as part of an ongoing capital project, electricity, maintenance contract, and staffing. Revenues were: savings from stopping USA referrals, avoiding the costs of standard radiation therapy (RT) for Albertans receiving PBT instead, and cost-recovery charges for out-of-province patients. Results The Ministry of Health funded 15 Albertans for PBT in the USA in the 2014/15 fiscal year (mean CAD$ 237,348/patient). A single-vault, compact PBT unit operating 10 hours/day could treat 250 patients annually. A 100 Albertans, with accepted indications, such as the curative-intent treatment of chordomas, ocular melanomas, and selected pediatric cancers, would likely benefit annually from PBT's improved conformality and/or reduced integral dose compared to RT. The estimated capital cost was $40 million for a single beamline built within an ongoing capital project. Operating costs were $4.8 million/year at capacity. With 50% capacity reserved for non-Albertans at a cost recovery of $45,000/patient, a Western Canadian PBT facility would achieve net positive cash flow by year eight of clinical operations, assuming Alberta-to-USA referrals reach 21 patients/year by 2024 and increase at 3%/year thereafter. Sensitivity analysis indicates the lifetime net savings is robust to the assumptions made. Conclusion This business case, based on Canadian costing data and estimates, demonstrates the potential for a financially viable PBT facility in Western Canada.
RESUMO
(2E,4E,6Z,8Z)-8-(3',4'-Dihydro-1'(2H)-naphthalen-1'-ylidene)-3,7-dimethyl-2,3,6-octatrienoinic acid (UAB30) is currently undergoing clinical evaluation as a novel cancer prevention agent. In efforts to develop even more highly potent rexinoids that prevent breast cancer without toxicity, we further explore here the structure-activity relationship of two separate classes of rexinoids. UAB30 belongs to the class II rexinoids and possesses a 9Z-tetraenoic acid chain bonded to a tetralone ring, whereas the class I rexinoids contain the same 9Z-tetraenoic acid chain bonded to a disubstituted cyclohexenyl ring. Among the 12 class I and class II rexinoids evaluated, the class I rexinoid 11 is most effective in preventing breast cancers in an in vivo rat model alone or in combination with tamoxifen. Rexinoid 11 also reduces the size of established tumors and exhibits a therapeutic effect. However, 11 induces hypertriglyceridemia at its effective dose. On the other hand rexinoid 10 does not increase triglyceride levels while being effective in the in vivo chemoprevention assay. X-ray studies of four rexinoids bound to the ligand binding domain of the retinoid X receptor reveal key structural aspects that enhance potency as well as those that enhance the synthesis of lipids.
Assuntos
Anticarcinógenos/química , Anticarcinógenos/farmacologia , Ácidos Graxos Insaturados/química , Neoplasias Mamárias Experimentais/prevenção & controle , Naftalenos/química , Relação Estrutura-Atividade , Animais , Anticarcinógenos/efeitos adversos , Anticarcinógenos/metabolismo , Sítios de Ligação , Técnicas de Química Sintética , Cristalografia por Raios X , Dislipidemias/induzido quimicamente , Dislipidemias/metabolismo , Feminino , Humanos , Neoplasias Mamárias Experimentais/induzido quimicamente , Conformação Molecular , Ratos Sprague-Dawley , Receptor X Retinoide alfa/química , Receptor X Retinoide alfa/metabolismo , Tamoxifeno/farmacologia , Triglicerídeos/sangueRESUMO
(2E,4E,6Z,8E)-8-(3',4'-Dihydro-1'(2'H)-naphthalen-1'-ylidene)-3,7-dimethyl-2,4,6-octatrienoic acid, 9cUAB30, is a selective rexinoid that displays substantial chemopreventive capacity with little toxicity. 4-Methyl-UAB30, an analogue of 9cUAB30, is a potent RXR agonist but caused increased lipid biosynthesis unlike 9cUAB30. To evaluate how methyl substitution influenced potency and lipid biosynthesis, we synthesized four 9cUAB30 homologues with methyl substitutions at the 5-, 6-, 7-, or 8-position of the tetralone ring. The syntheses and biological evaluations of these new analogues are reported here along with the X-ray crystal structures of each homologue bound to the ligand binding domain of hRXRα. We demonstrate that each homologue of 9cUAB30 is a more potent agonist, but only the 7-methyl-9cUAB30 caused severe hyperlipidemia in rats. On the basis of the X-ray crystal structures of these new rexinoids and bexarotene (Targretin) bound to hRXRα-LBD, we reveal that each rexinoid, which induced hyperlipidemia, had methyl groups that interacted with helix 7 residues of the LBD.
Assuntos
Anticarcinógenos/química , Ácidos Graxos Insaturados/química , Hiperlipidemias/induzido quimicamente , Naftalenos/química , Receptor X Retinoide alfa/agonistas , Animais , Anticarcinógenos/farmacologia , Anticarcinógenos/toxicidade , Apoptose/efeitos dos fármacos , Bexaroteno , Sítios de Ligação , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Transformação Celular Neoplásica/efeitos dos fármacos , Cristalografia por Raios X , Ácidos Graxos Insaturados/farmacologia , Ácidos Graxos Insaturados/toxicidade , Feminino , Humanos , Neoplasias Mamárias Experimentais/patologia , Neoplasias Mamárias Experimentais/prevenção & controle , Modelos Moleculares , Estrutura Molecular , Naftalenos/farmacologia , Naftalenos/toxicidade , Ratos , Receptor X Retinoide alfa/genética , Estereoisomerismo , Relação Estrutura-Atividade , Tetra-Hidronaftalenos/farmacologia , Tetra-Hidronaftalenos/toxicidade , Ativação TranscricionalRESUMO
(2E,4E,6Z,8Z)-8-(3',4'-Dihydro-1'(2H)-naphthalen-1'-ylidene)-3,7-dimethyl-2,3,6-octatrienoinic acid, 9cUAB30, is a selective rexinoid for the retinoid X nuclear receptors (RXR). 9cUAB30 displays substantial chemopreventive capacity with little toxicity and is being translated to the clinic as a novel cancer prevention agent. To improve on the potency of 9cUAB30, we synthesized 4-methyl analogs of 9cUAB30, which introduced chirality at the 4-position of the tetralone ring. The syntheses and biological evaluations of the racemic homolog and enantiomers are reported. We demonstrate that the S-enantiomer is the most potent and least toxic even though these enantiomers bind in a similar conformation in the ligand binding domain of RXR.
Assuntos
Neoplasias/prevenção & controle , Neoplasias/terapia , Receptores X de Retinoides/metabolismo , Retinoides/química , Humanos , Fator 4 Semelhante a Kruppel , Ligantes , Conformação Molecular , Retinoides/metabolismoRESUMO
Retinoid X receptors (RXRs) are obligate partners for several other nuclear receptors, and they play a key role in several signaling processes. Despite being a promiscuous heterodimer partner, this nuclear receptor is a target of therapeutic intervention through activation using selective RXR agonists (rexinoids). Agonist binding to RXR initiates a large conformational change in the receptor that allows for coactivator recruitment to its surface and enhanced transcription. Here we reveal the structural and dynamical changes produced when a coactivator peptide binds to the human RXRα ligand binding domain containing two clinically relevant rexinoids, Targretin and 9-cis-UAB30. Our results show that the structural changes are very similar for each rexinoid and similar to those for the pan-agonist 9-cis-retinoic acid. The four structural changes involve key residues on helix 3, helix 4, and helix 11 that move from a solvent-exposed environment to one that interacts extensively with helix 12. Hydrogen-deuterium exchange mass spectrometry reveals that the dynamics of helices 3, 11, and 12 are significantly decreased when the two rexinoids are bound to the receptor. When the pan-agonist 9-cis-retinoic acid is bound to the receptor, only the dynamics of helices 3 and 11 are reduced. The four structural changes are conserved in all x-ray structures of the RXR ligand-binding domain in the presence of agonist and coactivator peptide. They serve as hallmarks for how RXR changes conformation and dynamics in the presence of agonist and coactivator to initiate signaling.
Assuntos
Ácidos Graxos Insaturados/metabolismo , Naftalenos/metabolismo , Coativador 2 de Receptor Nuclear/metabolismo , Receptor X Retinoide alfa/metabolismo , Tetra-Hidronaftalenos/metabolismo , Alitretinoína , Sequência de Aminoácidos , Bexaroteno , Sítios de Ligação , Cristalografia por Raios X , Ácidos Graxos Insaturados/química , Humanos , Ligantes , Modelos Moleculares , Dados de Sequência Molecular , Estrutura Molecular , Naftalenos/química , Coativador 2 de Receptor Nuclear/química , Ligação Proteica , Conformação Proteica , Multimerização Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Receptor X Retinoide alfa/química , Tetra-Hidronaftalenos/química , Tretinoína/química , Tretinoína/metabolismoRESUMO
3-Phosphoglycerate kinase (EC 2.7.2.3) is a key enzyme in the glycolytic pathway and catalyzes an important phosphorylation step leading to the production of ATP. The crystal structure of Plasmodium falciparum phosphoglycerate kinase (PfPGK) in the open conformation is presented in two different groups, namely I222 and P6(1)22. The structure in I222 space group is solved using MAD and refined at 3Å whereas that in P6(1)22A is solved using MR and refined at 2.7Å. I222 form has three monomers in asymmetric unit whereas P6(1)22 form has two monomers in the asymmetric unit. In both crystal forms a sulphate ion is located at the active site where ATP binds, but no Mg(2+) ion is observed. For the first time another sulphate ion is found at the basic patch where the 3-phosphate of 1,3-biphosphoglycerate normally binds. This was found in both chains of P6(1)22 form but only in chain A of I222 form.
Assuntos
Fosfoglicerato Quinase/química , Plasmodium falciparum/enzimologia , Ânions/química , Cristalografia por Raios X , Ácidos Difosfoglicéricos/química , Magnésio/química , Ligação Proteica , Conformação Proteica , Sulfatos/químicaRESUMO
Retinoid X receptors (RXRs) are ligand-dependent nuclear receptors, which are activated by the potent agonist 9-cis-retinoic acid (9cRA). 9cRA binds to the ligand binding domain (LBD) of RXRs and recruits coactivator proteins for gene transcription. Using isothermal titration calorimetry, the binding of a 13-mer coactivator peptide, GRIP-1, to the hRXRα-LBD homodimer complex containing 9cRA (hRXRα-LBD:9cRA:GRIP-1) is reported between 20 and 37 °C. ΔG is temperature independent (-8.5 kcal/mol), and GRIP-1 binding is driven by ΔH (-9.2 kcal/mol) at 25 °C. ΔC(p) is large and negative (-401 cal mol(-1) K(-1)). The crystal structure of hRXRα-LBD:9cRA:GRIP-1 is reported at 2.05 Å. When the structures of hRXRα-LBD:9cRA:GRIP-1 and hRXRα-LBD:9cRA ( 1FBY ) homodimers are compared, E453 and E456 on helix 12 bury and form ionic interactions with GRIP-1. R302 on helix 4 realigns to form new salt bridges to both E453 and E456. F277 (helix 3), F437 (helix 11), and F450 (helix 12) move toward the hydrophobic interior. The changes in the near-UV spectrum at 260 nm of the hRXRα-LBD:9cRA:GRIP-1 support this structural change. Helix 11 tilts toward helix 12 by ≈1 Å, modifying the ring conformation of 9cRA. Hydrogen-deuterium exchange mass spectroscopy indicates GRIP-1 binding to hRXRα-LBD:9cRA significantly decreases the exchange rates for peptides containing helices 3 (F277), 4 (R302), 11 (F437), and 12 (E453, E456). The structural changes and loss of dynamics of the GRIP-1-bound structure are used to interpret the energetics of coactivator peptide binding to the agonist-bound hRXRα-LBD.
Assuntos
Coativador 2 de Receptor Nuclear/metabolismo , Receptor X Retinoide alfa/metabolismo , Tretinoína/metabolismo , Alitretinoína , Sequência de Aminoácidos , Cristalografia por Raios X , Humanos , Ligantes , Modelos Moleculares , Dados de Sequência Molecular , Coativador 2 de Receptor Nuclear/química , Ligação Proteica , Multimerização Proteica , Estrutura Terciária de Proteína , Receptor X Retinoide alfa/química , Espectrofotometria Ultravioleta , Termodinâmica , Tretinoína/químicaRESUMO
Vesicular trafficking may play a crucial role in the pathogenesis and survival of the malaria parasite. ADP-ribosylation factors (ARFs) are among the major components of vesicular trafficking pathways in eukaryotes. The crystal structure of ARF1 GTPase from Plasmodium falciparum has been determined in the GDP-bound conformation at 2.5â Å resolution and is compared with the structures of mammalian ARF1s.
Assuntos
Fator 1 de Ribosilação do ADP/química , Plasmodium falciparum/enzimologia , Sequência de Aminoácidos , Animais , Humanos , Modelos Moleculares , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Alinhamento de Sequência , Homologia Estrutural de ProteínaRESUMO
Nicotinic acid mononucleotide adenylyltransferase (NaMNAT; EC 2.7.7.18) is the penultimate enzyme in the biosynthesis of NAD(+) and catalyzes the adenylation of nicotinic acid mononucleotide (NaMN) by ATP to form nicotinic acid adenine dinucleotide (NaAD). This enzyme is regarded as a suitable candidate for antibacterial drug development; as such, Bacillus anthracis NaMNAT (BA NaMNAT) was heterologously expressed in Escherichia coli for the purpose of inhibitor discovery and crystallography. The crystal structure of BA NaMNAT was determined by molecular replacement, revealing two dimers per asymmetric unit, and was refined to an R factor and R(free) of 0.228 and 0.263, respectively, at 2.3 A resolution. The structure is very similar to that of B. subtilis NaMNAT (BS NaMNAT), which is also a dimer, and another independently solved structure of BA NaMNAT recently released from the PDB along with two ligated forms. Comparison of these and other less related bacterial NaMNAT structures support the presence of considerable conformational heterogeneity and flexibility in three loops surrounding the substrate-binding area.
Assuntos
Bacillus anthracis/enzimologia , Nicotinamida-Nucleotídeo Adenililtransferase/química , Sequência de Aminoácidos , Bacillus anthracis/genética , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Sequência Conservada , Modelos Moleculares , Dados de Sequência Molecular , NAD/biossíntese , Nicotinamida-Nucleotídeo Adenililtransferase/genética , Nicotinamida-Nucleotídeo Adenililtransferase/metabolismo , Conformação Proteica , Alinhamento de SequênciaRESUMO
Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian brain. The GABA receptor type C (GABA(C)) is a ligand-gated ion channel with pharmacological properties distinct from the GABA(A) receptor. To date, only three binding domains in the recombinant rho1 GABA(C) receptor have been recognized among six potential regions. In this report, using the substituted cysteine accessibility method, we scanned three potential regions previously unexplored in the rho1 GABA(C) receptor, corresponding to the binding loops A, E, and F in the structural model for ligand-gated ion channels. The cysteine accessibility scanning and agonist/antagonist protection tests have resulted in the identification of residues in loops A and E, but not F, involved in forming the GABA(C) receptor agonist binding pocket. Three of these newly identified residues are in a novel region corresponding to the extended stretch of loop E. In addition, the cysteine accessibility pattern suggests that part of loop A and part of loop E have a beta-strand structure, whereas loop F is a random coil. Finally, when all of the identified ligand binding residues are mapped onto a three-dimensional homology model of the amino-terminal domain of the rho1 GABA(C) receptor, they are facing toward the putative binding pocket. Combined with previous findings, a complete model of the GABA(C) receptor binding pocket was proposed and discussed in comparison with the GABA(A) receptor binding pocket.
Assuntos
Agonistas GABAérgicos/metabolismo , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Receptores de GABA/química , Receptores de GABA/metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Cisteína/genética , Cisteína/metabolismo , Relação Dose-Resposta a Droga , Agonistas GABAérgicos/química , Agonistas GABAérgicos/farmacologia , Antagonistas GABAérgicos/química , Antagonistas GABAérgicos/metabolismo , Antagonistas GABAérgicos/farmacologia , Humanos , Modelos Moleculares , Dados de Sequência Molecular , Mutação/genética , Propilaminas/química , Propilaminas/metabolismo , Propilaminas/farmacologia , Subunidades Proteicas/genética , Receptores de GABA/genética , Receptores de GABA-A/química , Receptores de GABA-A/metabolismo , Ácido gama-Aminobutírico/farmacologiaRESUMO
Electrospray ionization (ESI) mass spectra have been recorded for a range of substituted nitronyl nitroxide and iminyl nitroxide monoradicals and biradicals. Secondary species formed in the ESI source were observed as the dominant ions in both the iminyl nitroxide and nitronyl nitroxide spectra. Daughter ion spectrometry was used to establish fragmentation mechanisms for the nitronyl nitroxide and iminyl nitroxide moieties as well as the secondary species under ESI conditions.
RESUMO
Spontaneous formation of isoaspartyl residues (isoAsp) disrupts the structure and function of many normal proteins. Protein isoaspartyl methyltransferase (PIMT) reverts many isoAsp residues to aspartate as a protein repair process. We have determined the crystal structure of human protein isoaspartyl methyltransferase (HPIMT) complexed with adenosyl homocysteine (AdoHcy) to 1.6-A resolution. The core structure has a nucleotide binding domain motif, which is structurally homologous with the N-terminal domain of the bacterial Thermotoga maritima PIMT. Highly conserved residues in PIMTs among different phyla are placed at positions critical to AdoHcy binding and orienting the isoAsp residue substrate for methylation. The AdoHcy is completely enclosed within the HPIMT and a conformational change must occur to allow exchange with adenosyl methionine (AdoMet). An ordered sequential enzyme mechanism is supported because C-terminal residues involved with AdoHcy binding also form the isoAsp peptide binding site, and a change of conformation to allow AdoHcy to escape would preclude peptide binding. Modeling experiments indicated isoAsp groups observed in some known protein crystal structures could bind to the HPIMT active site.