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Articles by W Tan
Total Records ( 3 ) for W Tan
  C Wu , Z Hu , D Yu , L Huang , G Jin , J Liang , H Guo , W Tan , M Zhang , J Qian , D Lu , T Wu , D Lin and H. Shen

Recent three genome-wide association studies have mapped a lung cancer susceptibility locus to chromosome 15q25 in Caucasians. However, the reported risk single nucleotide polymorphisms (SNPs) are extremely rare in Asians, arguing against any of these being causative variants. This study sought to identify other variants on 15q25 associated with lung cancer susceptibility in Chinese. Two-stage case-control studies were conducted in subjects derived from both Northern and Southern China. The first-stage, consisting of 576 cases and 576 controls, was to discover novel risk variants using a haplotype-tagging SNP approach, and these variants were then replicated in the second-stage, consisting of 2,989 cases and 2,880 controls. Associations were estimated by logistic regression models, and function of the variants was examined by biochemical assays. We found that the three risk SNPs reported in Caucasians were not associated with lung cancer risk in Chinese. However, we identified four novel SNPs (rs2036534C>T, rs667282C>T, rs12910984G>A, and rs6495309T>C) that were associated with significantly increased lung cancer risk and smoking behavior, which were all confirmed in the replication analyses [odds ratios (95% confidence intervals) in the dominant model: 1.39 (1.23–1.57; P = 2.3 x 10–7), 1.52 (1.35–1.71; P = 2.0 x 10–12), 1.44 (1.28–1.63; P = 2.7 x 10–9), and 1.43 (1.27–1.61; P = 2.6 x 10–9), respectively]. We characterized the rs6495309T>C change in the CHRNA3 promoter as a functional variant because it affected the Oct-1 binding ability, resulting in increased CHRNA3 expression. These results support 15q25 as a susceptibility region for lung cancer in Chinese but underscore the difference in genetic markers among different ethnic populations. [Cancer Res 2009;69(12):5065–72]

  Q Li , Y Guo , Q Ou , C Cui , W. J Wu , W Tan , X Zhu , L. B Lanceta , S. K Sanganalmath , B Dawn , K Shinmura , G. D Rokosh , S Wang and R. Bolli

Background— Although inducible nitric oxide synthase (iNOS) is known to impart powerful protection against myocardial infarction, the mechanism for this salubrious action remains unclear.

Methods and Results— Adenovirus-mediated iNOS gene transfer in mice resulted 48 to 72 hours later in increased expression not only of iNOS protein but also of heme oxygenase (HO)-1 mRNA and protein; HO-2 protein expression did not change. iNOS gene transfer markedly reduced infarct size in wild-type mice, but this effect was completely abrogated in HO-1–/– mice. At 48 hours after iNOS gene transfer, nuclear factor-B was markedly activated. In transgenic mice with cardiomyocyte-restricted expression of a dominant negative mutant of IB (IBS32A,S36A), both basal HO-1 levels and upregulation of HO-1 by iNOS gene transfer were suppressed. Chromatin immunoprecipitation analysis of mouse hearts provided direct evidence that nuclear factor-B subunits p50 and p65 were recruited to the HO-1 gene promoter (–468 to –459 bp) 48 hours after iNOS gene transfer.

Conclusions— This study demonstrates for the first time the existence of a close functional coupling between cardiac iNOS and cardiac HO-1: iNOS upregulates HO-1 by augmenting nuclear factor-B binding to the region of the HO-1 gene promoter from –468 to –459 bp, and HO-1 then mediates the cardioprotective effects of iNOS. These results also reveal an important role of nuclear factor-B in both basal and iNOS-induced expression of cardiac HO-1. Collectively, the present findings significantly expand our understanding of the regulation of cardiac HO-1 and of the mechanism whereby iNOS exerts its cardioprotective actions.

  S. B Pruett , B Cheng , R Fan , W Tan and T. Sebastian

Sodium methyldithiocarbamate (SMD) is the third most abundantly used conventional pesticide in the United States, and hundreds of thousands of persons are exposed to this compound or its major breakdown product, methylisothiocyanate, at levels greater than recommended by the Environmental Protection Agency. A previous study suggests three mechanisms of action involved to some degree in the inhibition of inflammation and decreased resistance to infection caused by exposure of mice to the compound. One of these mechanisms is oxidative stress. The purpose of the present study was to confirm that this mechanism is involved in the effects of SMD on cytokine production by peritoneal macrophages and to further characterize its role in altered cytokine production. Results indicated that SMD significantly decreased the intracellular concentration of reduced glutathione (GSH), suggesting oxidative stress. This was further indicated by the upregulation of genes involved in the "response to oxidative stress" as determined by microarray analysis. These effects were associated with the inhibition of lipopolysaccharide (LPS)-induced production of several proinflammatory cytokines. Experimental depletion of GSH with buthionine sulfoximine (BSO) partially prevented the decrease in LPS-induced interleukin (IL)-6 production caused by SMD and completely prevented the decrease in IL-12. In contrast, BSO plus SMD substantially enhanced the production of IL-10. These results along with results from a previous study are consistent with the hypothesis that SMD causes oxidative stress, which contributes to modulation of cytokine production. However, oxidative stress alone cannot explain the increased IL-10 production caused by SMD.

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