bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of the E540V Amino Acid Substitution in GyrB of
Mycobacterium tuberculosis
on Quinolone Resistance
Authors: Kim Hyun , Nakajima Chie , Yokoyama Kazumasa , Rahim Zeaur , Kim Youn Uck , Oguri Hiroki , Suzuki Yasuhiko 
Published: June 2011

ABSTRACT

Amino acid substitutions conferring resistance to quinolones in
Mycobacterium tuberculosis
have generally been found within the quinolone resistance-determining regions (QRDRs) in the A subunit of DNA gyrase (GyrA) rather than the B subunit of DNA gyrase (GyrB). To clarify the contribution of an amino acid substitution, E540V, in GyrB to quinolone resistance in
M. tuberculosis
, we expressed recombinant DNA gyrases in
Escherichia coli
and characterized them
in vitro
. Wild-type and GyrB-E540V DNA gyrases were reconstituted
in vitro
by mixing recombinant GyrA and GyrB. Correlation between the amino acid substitution and quinolone resistance was assessed by the ATP-dependent DNA supercoiling assay, quinolone-inhibited supercoiling assay, and DNA cleavage assay. The 50% inhibitory concentrations of eight quinolones against DNA gyrases bearing the E540V amino acid substitution in GyrB were 2.5- to 36-fold higher than those against the wild-type enzyme. Similarly, the 25% maximum DNA cleavage concentrations were 1.5- to 14-fold higher for the E540V gyrase than for the wild-type enzyme. We further demonstrated that the E540V amino acid substitution influenced the interaction between DNA gyrase and the substituent(s) at R-7, R-8, or both in quinolone structures. This is the first detailed study of the contribution of the E540V amino acid substitution in GyrB to quinolone resistance in
M. tuberculosis
.
Pharmacokinetics, Pharmacodynamics, and Allometric Scaling of Chloroquine in a Murine Malaria Model
Authors: Moore Brioni R. , Page-Sharp Madhu , Stoney Jillian R. , Ilett Kenneth F. , Jago Jeffrey D. , Batty Kevin T. 
Published: June 2011

ABSTRACT

Chloroquine (CQ) is an important antimalarial drug for the treatment of special patient groups and as a comparator for preclinical testing of new drugs. Pharmacokinetic data for CQ in animal models are limited; thus, we conducted a three-part investigation, comprising (i) pharmacodynamic studies of CQ and CQ plus dihydroartemisinin (DHA) in
Plasmodium berghei
-infected mice, (ii) pharmacokinetic studies of CQ in healthy and malaria-infected mice, and (iii) interspecies allometric scaling for CQ from 6 animal and 12 human studies. The single-dose pharmacodynamic study (10 to 50 mg CQ/kg of body weight) showed dose-related reduction in parasitemia (5- to >500-fold) and a nadir 2 days after the dose. Multiple-dose regimens (total dose, 50 mg/kg CQ) demonstrated a lower nadir and longer survival time than did the same single dose. The CQ-DHA combination provided an additive effect compared to each drug alone. The elimination half-life (
t
1/2
), clearance (CL), and volume of distribution (
V
) of CQ were 46.6 h, 9.9 liters/h/kg, and 667 liters/kg, respectively, in healthy mice and 99.3 h, 7.9 liters/h/kg, and 1,122 liters/kg, respectively, in malaria-infected mice. The allometric equations for CQ in healthy mammals (CL = 3.86 ×
W
0.56
,
V
= 230 ×
W
0.94
, and
t
1/2
= 123 ×
W
0.2
) were similar to those for malaria-infected groups. CQ showed a delayed dose-response relationship in the murine malaria model and additive efficacy when combined with DHA. The biphasic pharmacokinetic profiles of CQ are similar across mammalian species, and scaling of specific parameters is plausible for preclinical investigations.
Low Fitness Cost of the Multidrug Resistance Gene
cfr
Authors: LaMarre Jacqueline M. , Locke Jeffrey B. , Shaw Karen J. , Mankin Alexander S. 
Published: June 2011

ABSTRACT

The recently described rRNA methyltransferase Cfr that methylates the conserved 23S rRNA residue A2503, located in a functionally critical region of the ribosome, confers resistance to an array of ribosomal antibiotics, including linezolid. A number of reports of linezolid-resistant
cfr
-positive clinical strains indicate the possible rapid spread of this resistance mechanism. Since the rate of dissemination and the efficiency of maintenance of a resistance gene depend on the fitness cost associated with its acquisition, we investigated the fitness cost of
cfr
expression in a laboratory
Staphylococcus aureus
strain. We found that acquisition of the
cfr
gene does not produce any appreciable reduction in the cell growth rate. Only in a cogrowth competition experiment was some loss of fitness observed because Cfr-expressing cells slowly lose to the
cfr
-negative control strain. Interestingly, cells expressing wild-type and catalytically inactive Cfr had very similar growth characteristics, indicating that the slight fitness cost associated with
cfr
acquisition stems from expression of the Cfr polypeptide rather than from the modification of the conserved rRNA residue. In some clinical isolates,
cfr
is coexpressed with the
erm
gene, which encodes a methyltransferase targeting another 23S rRNA residue, A2058. Dimethylation of A2058 by Erm notably increases the fitness cost associated with the Cfr-mediated methylation of A2503. The generally low fitness cost of
cfr
acquisition observed in our experiments with the laboratory
S. aureus
strain offers a microbiological explanation for the apparent spread of the
cfr
gene among pathogens.
The
pmrCAB
Operon Mediates Polymyxin Resistance in
Acinetobacter baumannii
ATCC 17978 and Clinical Isolates through Phosphoethanolamine Modification of Lipid A
Authors: Arroyo Luis A. , Herrera Carmen M. , Fernandez Lucia , Hankins Jessica V. , Trent M. Stephen , Hancock Robert E. W. 
Published: June 2011

ABSTRACT

The emergence of multidrug resistance among
Acinetobacter baumannii
is leading to an increasing dependence on the use of polymyxins as last-hope antibiotics. Here, we utilized genetic and biochemical methods to define the involvement of the
pmrCAB
operon in polymyxin resistance in this organism. Sequence analysis of 16 polymyxin B-resistant strains, including 6 spontaneous mutants derived from strain ATCC 17978 and 10 clinical isolates from diverse sources, revealed that they had independent mutations in the
pmrB
gene, encoding a sensor kinase, or in the response regulator PmrA. Knockout of the
pmrB
gene in two mutants and two clinical isolates led to a decrease in the polymyxin B susceptibility of these strains, which could be restored with the cloned
pmrAB
genes from the mutants but not from the wild type. Reverse transcription-quantitative PCR (RT-qPCR) analysis also showed a correlation between the expression of
pmrC
and polymyxin B resistance. Characterization of lipid A species from the mutant strains, by thin-layer chromatography and mass spectrometry, indicated that the addition of phosphoethanolamine to lipid A correlated with resistance. This addition is performed in
Salmonella enterica
serovar Typhimurium by the product of the
pmrC
gene, which is a homolog of the
pmrC
gene from
Acinetobacter
. Knockout of this gene in the mutant R2 [
pmrB
(
T235I
)] reversed resistance as well as phosphoethanolamine modification of lipid A. These results demonstrate that specific alterations in the sequence of the
pmrCAB
operon are responsible for resistance to polymyxins in
A. baumannii
.
Commonality among Fluoroquinolone-Resistant Sequence Type ST131 Extraintestinal
Escherichia coli
Isolates from Humans and Companion Animals in Australia
Authors: Platell Joanne L. , Cobbold Rowland N. , Johnson James R. , Heisig Anke , Heisig Peter , Clabots Connie , Kuskowski Michael A. , Trott Darren J. 
Published: June 2011

ABSTRACT

Escherichia coli
sequence type 131 (ST131), an emergent multidrug-resistant extraintestinal pathogen, has spread epidemically among humans and was recently isolated from companion animals. To assess for human-companion animal commonality among ST131 isolates, 214 fluoroquinolone-resistant extraintestinal
E. coli
isolates (205 from humans, 9 from companion animals) from diagnostic laboratories in Australia, provisionally identified as ST131 by PCR, selectively underwent PCR-based O typing and
bla
CTX-M-15
detection. A subset then underwent multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) analysis, extended virulence genotyping, antimicrobial susceptibility testing, and fluoroquinolone resistance genotyping. All isolates were O25b positive, except for two O16 isolates and one O157 isolate, which (along with six O25b-positive isolates) were confirmed by MLST to be ST131. Only 12% of isolates (25 human, 1 canine) exhibited
bla
CTX-M-15
. PFGE analysis of 20 randomly selected human and all 9 companion animal isolates showed multiple instances of ≥94% profile similarity across host species; 12 isolates (6 human, 6 companion animal) represented pulsotype 968, the most prevalent ST131 pulsotype in North America (representing 23% of a large ST131 reference collection). Virulence gene and antimicrobial resistance profiles differed minimally, without host species specificity. The analyzed ST131 isolates also exhibited a conserved, host species-independent pattern of chromosomal fluoroquinolone resistance mutations. However, eight (89%) companion animal isolates, versus two (10%) human isolates, possessed the plasmid-borne
qnrB
gene (
P
< 0.001). This extensive across-species strain commonality, plus the similarities between Australian and non-Australian ST131 isolates, suggest that ST131 isolates are exchanged between humans and companion animals both within Australia and intercontinentally.
Bacterial Virulence in the Moonlight: Multitasking Bacterial Moonlighting Proteins Are Virulence Determinants in Infectious Disease
Authors: Henderson Brian , Martin Andrew 
Published: June 2011

ABSTRACTMen may not be able to multitask, but it is emerging that proteins can. This capacity of proteins to exhibit more than one function is termed protein moonlighting, and, surprisingly, many highly conserved proteins involved in metabolic regulation or the cell stress response have a range of additional biological actions which are involved in bacterial virulence. This review highlights the multiple roles exhibited by a range of bacterial proteins, such as glycolytic and other metabolic enzymes and molecular chaperones, and the role that such moonlighting activity plays in the virulence characteristics of a number of important human pathogens, includingStaphylococcus aureus,Streptococcus pyogenes,Streptococcus pneumoniae,Helicobacter pylori, andMycobacterium tuberculosis.
Bacteriophage-Encoding Cytolethal Distending Toxin Type V Gene Induced from Nonclinical Escherichia coli Isolates
Authors: Allué-Guardia Anna , García-Aljaro Cristina , Muniesa Maite 
Published: June 2011

ABSTRACT

Cytolethal distending toxin (Cdt) is produced by a variety of pathogenic bacteria, including pathogenic serotypes of Shiga toxin-producing
Escherichia coli
(STEC). The Cdt family comprises five variants (Cdt-I to Cdt-V) encoded by three genes located within the chromosome or plasmids or, in the case of Cdt-I, within bacteriophages. In this study, we evaluated the occurrence of the
cdt
gene in a collection of 140 environmental STEC isolates.
cdt
was detected in 12.1% of strains, of which five strains carried inducible bacteriophages containing the Cdt-V variant. Two Cdt-V phages of the
Siphoviridae
morphology lysogenized
Shigella sonnei
, generating two lysogens: a single Cdt phage lysogen and a double lysogen, containing a Cdt phage and an Stx phage, both from the wild-type strain. The rates of induction of Cdt phages were evaluated by quantitative PCR, and spontaneous induction of Cdt-V phage was observed, whereas induction of Stx phage in the double lysogen was mitomycin C dependent. The Cdt distending effect was observed in HeLa cells inoculated with the supernatant of the Cdt-V phage lysogen. A ClaI fragment containing the
cdt-V
gene of one phage was cloned, and sequencing confirmed the presence of Cdt-V, as well as a fragment downstream from the
cdt
homolog to
gpA
, encoding a replication protein of bacteriophage P2. Evaluation of Cdt-V phages in nonclinical water samples showed densities of 10
2
to 10
9
gene copies in 100 ml, suggesting the high prevalence of Cdt phages in nonclinical environments.
Structure/Function Analysis of Neisseria meningitidis PilW, a Conserved Protein That Plays Multiple Roles in Type IV Pilus Biology
Authors: Szeto Tim H. , Dessen Andréa , Pelicic Vladimir 
Published: June 2011

ABSTRACT

Type IV pili (Tfp) are widespread filamentous bacterial organelles that mediate multiple functions and play a key role in pathogenesis in several important human pathogens, including
Neisseria meningitidis
. Tfp biology remains poorly understood at a molecular level because the roles of the numerous proteins that are involved remain mostly obscure. Guided by the high-resolution crystal structure we recently reported for
N. meningitidis
PilW, a widely conserved protein essential for Tfp biogenesis, we have performed a structure/function analysis by targeting a series of key residues through site-directed mutagenesis and analyzing the corresponding variants using an array of phenotypic assays. Here we show that PilW's involvement in the functionality of Tfp can be genetically uncoupled from its concurrent role in the assembly/stabilization of the secretin channels through which Tfp emerge on the bacterial surface. These findings suggest that PilW is a multifunctional protein.
High Phosphoantigen Levels in Bisphosphonate-Treated Human Breast Tumors Promote Vγ9Vδ2 T-Cell Chemotaxis and Cytotoxicity In Vivo
Authors: Benzaïd Ismahène , Mönkkönen Hannu , Stresing Verena , Bonnelye Edith , Green Jonathan , Mönkkönen Jukka , Touraine Jean-Louis , Clézardin Philippe 
Published: June 2011

Abstract
The nitrogen-containing bisphosphonate zoledronic acid (ZOL), a potent inhibitor of farnesyl pyrophosphate synthase, blocks the mevalonate pathway, leading to intracellular accumulation of isopentenyl pyrophosphate/triphosphoric acid I-adenosin-5′-yl ester 3-(3-methylbut-3-enyl) ester (IPP/ApppI) mevalonate metabolites. IPP/ApppI accumulation in ZOL-treated cancer cells may be recognized by Vγ9Vδ2 T cells as tumor phosphoantigens in vitro. However, the significance of these findings in vivo remains largely unknown. In this study, we investigated the correlation between the anticancer activities of Vγ9Vδ2 T cells and the intracellular IPP/ApppI levels in ZOL-treated breast cancer cells in vitro and in vivo. We found marked differences in IPP/ApppI production among different human breast cancer cell lines post-ZOL treatment. Coculture with purified human Vγ9Vδ2 T cells led to IPP/ApppI-dependent near-complete killing of ZOL-treated breast cancer cells. In ZOL-treated mice bearing subcutaneous breast cancer xenografts, Vγ9Vδ2 T cells infiltrated and inhibited growth of tumors that produced high IPP/ApppI levels, but not those expressing low IPP/ApppI levels. Moreover, IPP/ApppI not only accumulated in cancer cells but it was also secreted, promoting Vγ9Vδ2 T-cell chemotaxis to the tumor. Without Vγ9Vδ2 T-cell expansion, ZOL did not inhibit tumor growth. These findings suggest that cancers-producing high IPP/ApppI levels after ZOL treatment are most likely to benefit from Vγ9Vδ2 T-cell–mediated immunotherapy. Cancer Res; 71(13); 4562–72. ©2011 AACR.
Small-Molecule Anticancer Compounds Selectively Target the Hemopexin Domain of Matrix Metalloproteinase-9
Authors: Dufour Antoine , Sampson Nicole S. , Li Jian , Kuscu Cem , Rizzo Robert C. , DeLeon Jennifer L. , Zhi Jizu , Jaber Nadia , Liu Eric , Zucker Stanley , Cao Jian 
Published: June 2011

Abstract
Lack of target specificity by existing matrix metalloproteinase (MMP) inhibitors has hindered antimetastatic cancer drug discovery. Inhibitors that bind to noncatalytic sites of MMPs and disrupt protease signaling function have the potential to be more specific and selective. In this work, compounds that target the hemopexin (PEX) domain of MMP-9 were identified using an in silico docking approach and evaluated using biochemical and biological approaches. Two of the selected compounds interfere with MMP-9–mediated cancer cell migration and proliferation in cells expressing exogenous or endogenous MMP-9. Furthermore, these inhibitors do not modulate MMP-9 catalytic activity. The lead compound, N-[4-(difluoromethoxy)phenyl]-2-[(4-oxo-6-propyl-1H-pyrimidin-2-yl)sulfanyl]-acetamide, specifically binds to the PEX domain of MMP-9, but not other MMPs. This interaction between the compound and the PEX domain results in the abrogation of MMP-9 homodimerization and leads to blockage of a downstream signaling pathway required for MMP-9–mediated cell migration. In a tumor xenograft model, this pyrimidinone retarded MDA-MB-435 tumor growth and inhibited lung metastasis. Thus, we have shown for the first time that a novel small-molecule interacts specifically with the PEX domain of MMP-9 and inhibits tumor growth and metastasis by reducing cell migration and proliferation. Cancer Res; 71(14); 4977–88. ©2011 AACR.
18F-Fluorodeoxy-glucose Positron Emission Tomography Marks MYC-Overexpressing Human Basal-Like Breast Cancers
Authors: Palaskas Nicolaos , Larson Steven M. , Schultz Nikolaus , Komisopoulou Evangelia , Wong Justin , Rohle Dan , Campos Carl , Yannuzzi Nicolas , Osborne Joseph R. , Linkov Irina , Kastenhuber Edward R. , Taschereau Richard , Plaisier Seema B. , Tran Chris , Heguy Adriana , Wu Hong , Sander Chris , Phelps Michael E. , Brennan Cameron , Port Elisa , Huse Jason T. , Graeber Thomas G. , Mellinghoff Ingo K. 
Published: June 2011

Abstract
In contrast to normal cells, cancer cells avidly take up glucose and metabolize it to lactate even when oxygen is abundant, a phenomenon referred to as the Warburg effect. This fundamental alteration in glucose metabolism in cancer cells enables their specific detection by positron emission tomography (PET) following i.v. injection of the glucose analogue 18F-fluorodeoxy-glucose (18FDG). However, this useful imaging technique is limited by the fact that not all cancers avidly take up FDG. To identify molecular determinants of 18FDG retention, we interrogated the transcriptomes of human-cancer cell lines and primary tumors for metabolic pathways associated with 18FDG radiotracer uptake. From ninety-five metabolic pathways that were interrogated, the glycolysis, and several glycolysis-related pathways (pentose phosphate, carbon fixation, aminoacyl-tRNA biosynthesis, one-carbon-pool by folate) showed the greatest transcriptional enrichment. This “FDG signature” predicted FDG uptake in breast cancer cell lines and overlapped with established gene expression signatures for the “basal-like” breast cancer subtype and MYC-induced tumorigenesis in mice. Human breast cancers with nuclear MYC staining and high RNA expression of MYC target genes showed high 18FDG-PET uptake (P &lt; 0.005). Presence of the FDG signature was similarly associated with MYC gene copy gain, increased MYC transcript levels, and elevated expression of metabolic MYC target genes in a human breast cancer genomic dataset. Together, our findings link clinical observations of glucose uptake with a pathologic and molecular subtype of human breast cancer. Furthermore, they suggest related approaches to derive molecular determinants of radiotracer retention for other PET-imaging probes. Cancer Res; 71(15); 5164–74. ©2011 AACR.
Ex Vivo Graft Purging and Expansion of Autologous Blood Progenitor Cell Products from Patients with Multiple Myeloma
Authors: Yang Hong , Robinson Simon N. , Nieto Yago , Jones Richard J. , Gocke Christopher D. , Lu Junjun , Giralt Sergio A. , Jones Roy B. , Decker William K. , Xing Dongxia , Steiner David , Champlin Richard E. , McMannis John D. , Ng Jingjing , Thomas Michael W. , Shah Nina , Andersson Borje S. , Parmar Simrit , Shpall Elizabeth J. 
Published: June 2011

Abstract
Autologous peripheral blood progenitor cell (PBPC) transplantation is the treatment of choice for selected myeloma patients. However, tumor cells contaminating the apheresis product are a potential source of relapse. Here we report a sequential purging strategy targeting mature and immature clonogenic myeloma cell populations in the autograft. Thawed PBPC products of myeloma patients were treated with rituximab to kill CD138−20+ B cells (highly clonogenic immature cells), and bortezomib to target CD138+ cells (normal and differentiated myeloma plasma cells), followed by coculture with allogeneic mesenchymal stem cells (MSC) from normal donors. After 7 days of coculture, nonadherent cells were removed and cultured in the absence of MSC for an additional 7 days. Then, efficacy of purging (removal of CD138−20+ and CD138+ cells) was assessed by flow cytometry and PCR. We used our ex vivo purging strategy to treat frozen aphereses from 16 patients. CD138+ and CD138−20+(19+) cells present in the initial products were depleted more than 3 and 4 logs, respectively based on 106 flow-acquisition events, and to levels below the limit of detection by PCR. In contrast, total nucleated cell (TNC), CD34+ cell, and colony-forming cell numbers were increased by approximately 12 to 20, 8-, and 23-fold, respectively. Overall, ex vivo treatment of apheresis products with rituximab, bortezomib, and coculture with normal donor MSC depleted mature and immature myeloma cells from clinical aphereses while expanding the normal hematopoietic progenitor cell compartment. Cancer Res; 71(14); 5040–9. ©2011 AACR.
Decision Tree–Based Modeling of Androgen Pathway Genes and Prostate Cancer Risk
Authors: Barnholtz-Sloan Jill S. , Guan Xiaowei , Zeigler-Johnson Charnita , Meropol Neal J. , Rebbeck Timothy R. 
Published: June 2011

AbstractBackground: Inherited variability in genes that influence androgen metabolism has been associated with risk of prostate cancer. The objective of this analysis was to evaluate interactions for prostate cancer risk by using classification and regression tree (CART) models (i.e., decision trees), and to evaluate whether these interactive effects add information about prostate cancer risk prediction beyond that of “traditional” risk factors.Methods: We compared CART models with traditional logistic regression (LR) models for associations of factors with prostate cancer risk using 1,084 prostate cancer cases and 941 controls. All analyses were stratified by race. We used unconditional LR to complement and compare with the race-stratified CART results using the area under curve (AUC) for the receiver operating characteristic curves.Results: The CART modeling of prostate cancer risk showed different interaction profiles by race. For European Americans, interactions among CYP3A43 genotype, history of benign prostate hypertrophy, family history of prostate cancer, and age at consent revealed a distinct hierarchy of gene–environment and gene–gene interactions, whereas for African Americans, interactions among family history of prostate cancer, individual proportion of European ancestry, number of GGC androgen receptor repeats, and CYP3A4/CYP3A5 haplotype revealed distinct interaction effects from those found in European Americans. For European Americans, the CART model had the highest AUC whereas for African Americans, the LR model with the CART discovered factors had the largest AUC.Conclusion and Impact: These results provide new insight into underlying prostate cancer biology for European Americans and African Americans. Cancer Epidemiol Biomarkers Prev; 20(6); 1146–55. ©2011 AACR.