Publications by authors named "Nicholas D Ward"

15 Publications

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Small streams dominate US tidal reaches and will be disproportionately impacted by sea-level rise.

Sci Total Environ 2021 Jan 24;753:141944. Epub 2020 Aug 24.

Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99354, USA.

Rivers and streams represent <0.6% of the Earth's land surface but play a disproportionately large role in global biogeochemical cycles and provide locally relevant ecosystem services. However, knowledge of how rivers influence material budgets and ecosystem services has major gaps due to the lack of explicit consideration of tidally-influenced reaches. Focusing on the conterminous US, we provide a foundation for understanding the role of tidal streams. We find that 66% of tidal stream length is contributed from low order streams (< 4th order), and that terrestrial ecosystem production in low-lying coastal zones is 30% greater than in adjacent terrestrial ecosystems. This prevalence of small streams indicates that small coastal watersheds dominate tidally influenced spatial domains. Furthermore, we find that relative sea-level rise (RSLR) will have a disproportionate impact on low order tidal streams and their terrestrial interfaces - 1 m RSLR will decrease the tidal stream land-water interface by 17% and the total surface area of US tidal streams by 31%. Upstream reaches of tidal zones will be extended in response to RSLR, but gains will be more than offset by coastal losses because topographic gradients become steeper moving inland, and accretion rates may not keep pace with RSLR. These results highlight previously unrecognized dominance, high productivity, and disproportionate future loss of low-order coastal ecosystems. This indicates a critical need to focus research on small tidal stream systems under contemporary and future conditions.
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http://dx.doi.org/10.1016/j.scitotenv.2020.141944DOI Listing
January 2021

Representing the function and sensitivity of coastal interfaces in Earth system models.

Nat Commun 2020 05 18;11(1):2458. Epub 2020 May 18.

USGS Water Mission Area, Menlo Park, CA, 94025, USA.

Between the land and ocean, diverse coastal ecosystems transform, store, and transport material. Across these interfaces, the dynamic exchange of energy and matter is driven by hydrological and hydrodynamic processes such as river and groundwater discharge, tides, waves, and storms. These dynamics regulate ecosystem functions and Earth's climate, yet global models lack representation of coastal processes and related feedbacks, impeding their predictions of coastal and global responses to change. Here, we assess existing coastal monitoring networks and regional models, existing challenges in these efforts, and recommend a path towards development of global models that more robustly reflect the coastal interface.
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http://dx.doi.org/10.1038/s41467-020-16236-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7235091PMC
May 2020

Metabolic Profiling Reveals Biochemical Pathways Responsible for Eelgrass Response to Elevated CO and Temperature.

Sci Rep 2020 03 13;10(1):4693. Epub 2020 Mar 13.

Department of Ocean, Earth & Atmospheric Sciences, Old Dominion University, Norfolk, VA, 23429, USA.

As CO levels in Earth's atmosphere and oceans steadily rise, varying organismal responses may produce ecological losers and winners. Increased ocean CO can enhance seagrass productivity and thermal tolerance, providing some compensation for climate warming. However, the metabolic shifts driving the positive response to elevated CO by these important ecosystem engineers remain unknown. We analyzed whole-plant performance and metabolic profiles of two geographically distinct eelgrass (Zostera marina L.) populations in response to CO enrichment. In addition to enhancing overall plant size, growth and survival, CO enrichment increased the abundance of Calvin Cycle and nitrogen assimilation metabolites while suppressing the abundance of stress-related metabolites. Overall metabolome differences between populations suggest that some eelgrass phenotypes may be better suited than others to cope with an increasingly hot and sour sea. Our results suggest that seagrass populations will respond variably, but overall positively, to increasing CO concentrations, generating negative feedbacks to climate change.
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http://dx.doi.org/10.1038/s41598-020-61684-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7070064PMC
March 2020

Marked isotopic variability within and between the Amazon River and marine dissolved black carbon pools.

Nat Commun 2019 09 5;10(1):4018. Epub 2019 Sep 5.

Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057, Zürich, Switzerland.

Riverine dissolved organic carbon (DOC) contains charcoal byproducts, termed black carbon (BC). To determine the significance of BC as a sink of atmospheric CO and reconcile budgets, the sources and fate of this large, slow-cycling and elusive carbon pool must be constrained. The Amazon River is a significant part of global BC cycling because it exports an order of magnitude more DOC, and thus dissolved BC (DBC), than any other river. We report spatially resolved DBC quantity and radiocarbon (ΔC) measurements, paired with molecular-level characterization of dissolved organic matter from the Amazon River and tributaries during low discharge. The proportion of BC-like polycyclic aromatic structures decreases downstream, but marked spatial variability in abundance and ΔC values of DBC molecular markers imply dynamic sources and cycling in a manner that is incongruent with bulk DOC. We estimate a flux from the Amazon River of 1.9-2.7 Tg DBC yr that is composed of predominately young DBC, suggesting that loss processes of modern DBC are important.
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http://dx.doi.org/10.1038/s41467-019-11543-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6728373PMC
September 2019

Using CDOM optical properties for estimating DOC concentrations and pCO in the Lower Amazon River.

Opt Express 2018 Jul;26(14):A657-A677

Coloured dissolved organic matter (CDOM) is one of the major contributors to the absorption budget of most freshwaters and can be used as a proxy to assess non-optical carbon fractions such as dissolved organic carbon (DOC) and the partial pressure of carbon dioxide (pCO). Nevertheless, riverine studies that explore the former relationships are still relatively scarce, especially within tropical regions. Here we document the spatial-seasonal variability of CDOM, DOC and pCO, and assess the potential of CDOM absorption coefficient (a(412)) for estimating DOC concentration and pCO along the Lower Amazon River. Our results revealed differences in the dissolved organic matter (DOM) quality between clearwater (CW) tributaries and the Amazon River mainstream. A linear relationship between DOC and CDOM was observed when tributaries and mainstream are evaluated separately (Amazon River: N = 42, R = 0.74, p<0.05; CW: N = 13, R = 0.57, p<0.05). However, this linear relationship was not observed during periods of higher rainfall and river discharge, requiring a specific model for these time periods to be developed (N = 25, R = 0.58, p<0.05). A strong linear positive relation was found between a(412) and pCO(N = 69, R = 0.65, p<0.05) along the lower river. pCO was less affected by the optical difference between tributaries and mainstream waters or by the discharge conditions when compared to CDOM to DOC relationships. Including the river water temperature in the model improves our ability to estimate pCO (N = 69; R = 0.80, p<0.05). The ability to assess both DOC and pCO from CDOM optical properties opens further perspectives on the use of ocean colour remote sensing data for monitoring carbon dynamics in large running water systems worldwide.
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http://dx.doi.org/10.1364/OE.26.00A657DOI Listing
July 2018

Virioplankton Assemblage Structure in the Lower River and Ocean Continuum of the Amazon.

mSphere 2017 Sep-Oct;2(5). Epub 2017 Oct 4.

Laboratory of Microbiology, Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil.

The Amazon River watershed and its associated plume comprise a vast continental and oceanic area. The microbial activities along this continuum contribute substantially to global carbon and nutrient cycling, and yet there is a dearth of information on the diversity, abundance, and possible roles of viruses in this globally important river. The aim of this study was to elucidate the diversity and structure of virus assemblages of the Amazon River-ocean continuum. Environmental viral DNA sequences were obtained for 12 locations along the river's lower reach ( = 5) and plume ( = 7). Sequence assembly yielded 29,358 scaffolds, encoding 82,546 viral proteins, with 15 new complete viral genomes. Despite the spatial connectivity mediated by the river, virome analyses and physical-chemical water parameters clearly distinguished river and plume ecosystems. Bacteriophages were ubiquitous in the continuum and were more abundant in the transition region. Eukaryotic viruses occurred mostly in the river, while the plume had more viruses of autotrophic organisms (, ) and heterotrophic bacteria (). The viral families and were the most abundant and occurred throughout the continuum. The major functions of the genes in the continuum involved viral structures and life cycles, and viruses from plume locations and Tapajós River showed the highest levels of functional diversity. The distribution patterns of the viral assemblages were defined not only by the occurrence of possible hosts but also by water physical and chemical parameters, especially salinity. The findings presented here help to improve understanding of the possible roles of viruses in the organic matter cycle along the river-ocean continuum. The Amazon River forms a vast plume in the Atlantic Ocean that can extend for more than 1,000 km. Microbial communities promote a globally relevant carbon sink system in the plume. Despite the importance of viruses for the global carbon cycle, the diversity and the possible roles of viruses in the Amazon are poorly understood. The present work assesses, for the first time, the abundance and diversity of viruses simultaneously in the river and ocean in order to elucidate their possible roles. DNA sequence assembly yielded 29,358 scaffolds, encoding 82,546 viral proteins, with 15 new complete viral genomes from the 12 river and ocean locations. Viral diversity was clearly distinguished by river and ocean. Bacteriophages were the most abundant and occurred throughout the continuum. Viruses that infect eukaryotes were more abundant in the river, whereas phages appeared to have strong control over the host prokaryotic populations in the plume.
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http://dx.doi.org/10.1128/mSphere.00366-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5628290PMC
October 2017

Bacterial Biogeography across the Amazon River-Ocean Continuum.

Front Microbiol 2017 23;8:882. Epub 2017 May 23.

College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, CorvallisOR, United States.

Spatial and temporal patterns in microbial biodiversity across the Amazon river-ocean continuum were investigated along ∼675 km of the lower Amazon River mainstem, in the Tapajós River tributary, and in the plume and coastal ocean during low and high river discharge using amplicon sequencing of 16S rRNA genes in whole water and size-fractionated samples (0.2-2.0 μm and >2.0 μm). River communities varied among tributaries, but mainstem communities were spatially homogeneous and tracked seasonal changes in river discharge and co-varying factors. Co-occurrence network analysis identified strongly interconnected river assemblages during high (May) and low (December) discharge periods, and weakly interconnected transitional assemblages in September, suggesting that this system supports two seasonal microbial communities linked to river discharge. In contrast, plume communities showed little seasonal differences and instead varied spatially tracking salinity. However, salinity explained only a small fraction of community variability, and plume communities in blooms of diatom-diazotroph assemblages were strikingly different than those in other high salinity plume samples. This suggests that while salinity physically structures plumes through buoyancy and mixing, the composition of plume-specific communities is controlled by other factors including nutrients, phytoplankton community composition, and dissolved organic matter chemistry. Co-occurrence networks identified interconnected assemblages associated with the highly productive low salinity near-shore region, diatom-diazotroph blooms, and the plume edge region, and weakly interconnected assemblages in high salinity regions. This suggests that the plume supports a transitional community influenced by immigration of ocean bacteria from the plume edge, and by species sorting as these communities adapt to local environmental conditions. Few studies have explored patterns of microbial diversity in tropical rivers and coastal oceans. Comparison of Amazon continuum microbial communities to those from temperate and arctic systems suggest that river discharge and salinity are master variables structuring a range of environmental conditions that control bacterial communities across the river-ocean continuum.
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http://dx.doi.org/10.3389/fmicb.2017.00882DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5440517PMC
May 2017

Necrotizing Fasciitis of the Breast Requiring Emergent Radical Mastectomy.

Breast J 2017 Jan 16;23(1):95-99. Epub 2016 Sep 16.

Department of Surgery, Section of Endocrine Surgery, University of Kentucky, Lexington, Kentucky.

Necrotizing fasciitis is a rare, aggressive, soft-tissue infection that results in necrosis of skin, subcutaneous tissue, and fascia. It spreads rapidly and may progress to sepsis, multi-organ failure, and death. Predisposing conditions include diabetes, chronic alcoholism, advanced age, vascular disease, and immunosuppression and many cases are preceded by an injury or invasive procedure. Necrotizing soft-tissue infection of the breast is uncommon, with only a few reported cases in the literature. We present a 53-year-old diabetic woman who presented to the emergency room with several weeks of worsening breast and shoulder pain, swelling, and erythema. Upon formal evaluation by the surgical service, a necrotizing soft-tissue infection was suspected, and the patient was scheduled for emergent, surgical debridement. Because of the aggressive nature and high mortality of this disease, immediate surgical intervention, coupled with antibiotic therapy and physiologic support, is necessary to prevent complications and death.
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http://dx.doi.org/10.1111/tbj.12686DOI Listing
January 2017

Cost of ventral hernia repair using biologic or synthetic mesh.

J Surg Res 2016 06 4;203(2):459-65. Epub 2016 Mar 4.

Department of Surgery, University of Kentucky, Lexington, Kentucky.

Background: Patients undergoing ventral hernia repair (VHR) with biologic mesh (BioM) have higher hospital costs compared with synthetic mesh (SynM). This study compares 90-d pre- and post-VHR hospital costs (180-d) among BioM and SynM based on infection risk.

Methods: This retrospective National Surgical Quality Improvement Program study matched patient perioperative risk with resource utilization cost for a consecutive series of VHR repairs. Patient infection risks, clinical and financial outcomes were compared in unmatched SynM (n = 303) and BioM (n = 72) groups. Propensity scores were used to match 35 SynM and BioM pairs of cases with similar infection risk for outcomes analysis.

Results: BioM patients in the unmatched group were older with higher American Society of Anesthesiologists (ASA) and wound classification, and they more frequently underwent open repairs for recurrent hernias. Wound surgical site infections were more frequent in unmatched BioM patients (P = 0.001) as were 180-d costs ($43.8k versus $14.0k, P < 0.001). Propensity matching resulted in 31 clean cases. In these low-risk patients, wound occurrences and readmissions were identical, but 180-d costs remained higher ($31.8k versus $15.5k, P < 0.001). There were no differences in hospital 180-d diagnostic, emergency room, intensive care unit, floor, pharmacy, or therapeutic costs. However, 180-d operating room services and supply costs were higher in the BioM group ($21.1k versus $7.1k, P < 0.001).

Conclusions: BioM is used more commonly in hernia repairs involving higher wound class and ASA scores and recurrent hernias. Clinical outcomes after low-risk VHRs are similar; SynM utilization in low-risk hernia repairs was more cost-effective.
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http://dx.doi.org/10.1016/j.jss.2016.02.040DOI Listing
June 2016

Oxidative mitigation of aquatic methane emissions in large Amazonian rivers.

Glob Chang Biol 2016 Mar 9;22(3):1075-85. Epub 2016 Feb 9.

Center of Nuclear Energy in Agriculture, University of São Paulo, Av. Centenário, 303, Piracicaba, SP 13400-970, Brazil.

The flux of methane (CH4 ) from inland waters to the atmosphere has a profound impact on global atmospheric greenhouse gas (GHG) levels, and yet, strikingly little is known about the dynamics controlling sources and sinks of CH4 in the aquatic setting. Here, we examine the cycling and flux of CH4 in six large rivers in the Amazon basin, including the Amazon River. Based on stable isotopic mass balances of CH4 , inputs and outputs to the water column were estimated. We determined that ecosystem methane oxidation (MOX) reduced the diffusive flux of CH4 by approximately 28-96% and varied depending on hydrologic regime and general geochemical characteristics of tributaries of the Amazon River. For example, the relative amount of MOX was maximal during high water in black and white water rivers and minimal in clear water rivers during low water. The abundance of genetic markers for methane-oxidizing bacteria (pmoA) was positively correlated with enhanced signals of oxidation, providing independent support for the detected MOX patterns. The results indicate that MOX in large Amazonian rivers can consume from 0.45 to 2.07 Tg CH4 yr(-1) , representing up to 7% of the estimated global soil sink. Nevertheless, climate change and changes in hydrology, for example, due to construction of dams, can alter this balance, influencing CH4 emissions to atmosphere.
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http://dx.doi.org/10.1111/gcb.13169DOI Listing
March 2016

Venous Thromboembolism Prophylaxis For Esophagectomy: A Survey of Practice Patterns Among Thoracic Surgeons.

Ann Thorac Surg 2016 Feb 26;101(2):489-94. Epub 2015 Sep 26.

Department of Surgery, Division of Cardiothoracic Surgery, University of Kentucky, Lexington, Kentucky. Electronic address:

Background: Current guidelines for gastrointestinal cancer surgical intervention in high-risk patients recommend postoperative venous thromboembolism (VTE) chemical prophylaxis for 4 weeks with low-dose unfractionated heparin or low-molecular-weight heparin, but specific guidelines for esophagectomy are lacking. This survey identified the clinical patterns affecting postesophagectomy VTE chemoprophylaxis use among general thoracic surgeons.

Methods: General Thoracic Surgery Club members were invited to complete an online survey on VTE prophylaxis to analyze clinical factors affecting their choices.

Results: Seventy-seven surgeons (37% membership) responded; of these, 94% (72 of 77) completed fellowships, and 76% (58 of 77) worked at universities. VTE chemoprophylaxis administration varied widely in drug, dosing, and duration, with 30% using suboptimal dosing of unfractionated heparin (every 12 hours). Participants agreed that esophagectomy patients are at high VTE risk, yet 29% (22 of 76) of surgeons delay VTE chemoprophylaxis until postoperative day 1. Only 13% (10 of 77) prescribe postdischarge chemoprophylaxis. Minimally invasive surgeons (>90% of cases) were more likely to prescribe postdischarge prophylaxis (p = 0.007). Epidurals, routinely used by 65% (51 of 78), led to less compliance with recommended dosing. Only 53% (27 of 51) of pain teams allow unfractionated heparin every 8 hours, yet 73% (37 of 51) allow suboptimal dosing (every 12 h). Postoperative major complications were identified as a VTE risk factor by only 21% (15 of 72) of surgeons. Most (92% [68 of 74]) would follow esophagectomy-specific guidelines, if developed.

Conclusions: Thoracic surgeons agree that VTE chemoprophylaxis is necessary for esophagectomy, yet substantial variability exists in current practice. A noteworthy proportion use suboptimal dosing, and very few choose postdischarge prophylaxis. To improve postesophagectomy morbidity and mortality outcomes, thoracic surgeons are willing to follow evidence-based guidelines for VTE chemoprophylaxis.
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http://dx.doi.org/10.1016/j.athoracsur.2015.07.023DOI Listing
February 2016

Metagenomic and metatranscriptomic inventories of the lower Amazon River, May 2011.

Microbiome 2015 Sep 10;3:39. Epub 2015 Sep 10.

College of Earth, Ocean, and Atmospheric Science, Oregon State University, CEOAS Admin Bldg, Corvallis, OR, 97331-5503, USA.

Background: The Amazon River runs nearly 6500 km across the South American continent before emptying into the western tropical North Atlantic Ocean. In terms of both volume and watershed area, it is the world's largest riverine system, affecting elemental cycling on a global scale.

Results: A quantitative inventory of genes and transcripts benchmarked with internal standards was obtained at five stations in the lower Amazon River during May 2011. At each station, metagenomes and metatranscriptomes were obtained in duplicate for two microbial size fractions (free-living, 0.2 to 2.0 μm; particle-associated, 2.0 to 297 μm) using 150 × 150 paired-end Illumina sequencing. Forty eight sample datasets were obtained, averaging 15 × 10(6) potential protein-encoding reads each (730 × 10(6) total). Prokaryotic metagenomes and metatranscriptomes were dominated by members of the phyla Actinobacteria, Planctomycetes, Betaproteobacteria, Verrucomicrobia, Nitrospirae, and Acidobacteria. The actinobacterium SCGC AAA027-L06 reference genome recruited the greatest number of reads overall, with this single bin contributing an average of 50 billion genes and 500 million transcripts per liter of river water. Several dominant taxa were unevenly distributed between the free-living and particle-associated size fractions, such as a particle-associated bias for reads binning to planctomycete Schlesneria paludicola and a free-living bias for actinobacterium SCGC AAA027-L06. Gene expression ratios (transcripts to gene copy ratio) increased downstream from Óbidos to Macapá and Belém, indicating higher per cell activity of Amazon River bacteria and archaea as river water approached the ocean.

Conclusion: This inventory of riverine microbial genes and transcripts, benchmarked with internal standards for full quantitation, provides an unparalleled window into microbial taxa and functions in the globally important Amazon River ecosystem.
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http://dx.doi.org/10.1186/s40168-015-0099-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4564970PMC
September 2015

Esophageal fistula complicating thyroid lobectomy.

J Surg Case Rep 2015 Jan 7;2015(1). Epub 2015 Jan 7.

Department of Surgery, Section of Endocrine Surgery, University of Kentucky, Lexington, KY, USA

Thyroidectomy is associated with low morbidity and mortality. Esophageal perforation following thyroidectomy has been reported only three times previously, with subsequent fistulization occurring in two of these cases. The authors present the first such case report in the English-speaking literature.
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http://dx.doi.org/10.1093/jscr/rju136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4288288PMC
January 2015

Top Differential Diagnosis Should Be Microscopic Polyangiitis in ANCA-Positive Patient with Diffuse Pulmonary Hemorrhage and Hemosiderosis.

Case Rep Pathol 2014 30;2014:286030. Epub 2014 Nov 30.

Department of Anatomic Pathology, William Beaumont Hospital, 3601 W 13 Mile Road, Royal Oak, MI 48073, USA.

A rat model of antineutrophil cytoplasmic antibody (ANCA) associated vasculitides reveals crescentic glomerulonephritis as seen in human renal biopsies and diffuse lung hemorrhage that is not well documented in human lung biopsies. A 64-year-old male, with shortness of breath and mild elevation of serum creatinine, was found to have a positive serum test for ANCA, but negative antiglomerular basement membrane antibody. A renal biopsy showed pauci-immune type of crescentic glomerulonephritis and focal arteritis. The prior lung wedge biopsy was retrospectively reviewed to show diffuse hemorrhage and hemosiderosis with focal giant cells. In addition, small arteries revealed subtle neutrophil aggregation, and margination along vascular endothelium, but no definitive vasculitis. The pathology of ANCA associated vasculitides results from activated neutrophils by ANCA and subsequent activation of the alternative complement cascade with endothelial injury, neutrophil aggregation and margination. Our findings, after the correlation between lung biopsy and renal biopsy, imply that the top differential diagnosis in the lung biopsy should be microscopic polyangiitis when diffuse pulmonary hemorrhage and hemosiderosis are present in this ANCA-positive patient.
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http://dx.doi.org/10.1155/2014/286030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4265693PMC
December 2014

Fluorinated N,N-dialkylaminostilbenes repress colon cancer by targeting methionine S-adenosyltransferase 2A.

ACS Chem Biol 2013 Apr 6;8(4):796-803. Epub 2013 Feb 6.

Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, KY 40506-0509, USA.

Methionine S-adenosyltransferase 2A (MAT2A) is the catalytic subunit for synthesis of S-adenosylmethionine (SAM), the principal methyl donor in many biological processes. MAT2A is up-regulated in many cancers, including liver cancer and colorectal cancer (CRC) and is a potentially important drug target. We developed a family of fluorinated N,N-dialkylaminostilbene agents, called FIDAS agents, that inhibit the proliferation of CRC cells in vitro and in vivo. Using a biotinylated FIDAS analogue, we identified the catalytic subunit of MAT2A as the direct and exclusive binding target of these FIDAS agents. MAT2B, an associated regulatory subunit of MAT2A, binds indirectly to FIDAS agents through its association with MAT2A. FIDAS agents inhibited MAT2A activity in SAM synthesis, and depletion of MAT2A by shRNAs inhibited CRC cell growth. A novel FIDAS agent delivered orally repressed CRC xenografts in athymic nude mice. These findings suggest that FIDAS analogues targeting MAT2A represent a family of novel and potentially useful agents for cancer treatment.
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http://dx.doi.org/10.1021/cb3005353DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3631441PMC
April 2013