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Articles by X Ling
Total Records ( 2 ) for X Ling
  B Liu , D Chen , L Yang , Y Li , X Ling , L Liu , W Ji , Y Wei , J Wang , Q Wei , L Wang and J. Lu

Mitogen-activated protein kinase kinase 4 (MKK4) is a critical mediator of stress-activated protein kinase signals that regulate apoptosis, inflammations and tumorigenesis. Several polymorphisms have been identified in the MKK4 gene. We hypothesized that genetic variants in the MKK4 promoter may alter its expression and thus cancer risk. In a case–control study of 1056 lung cancer cases and 1056 sex and age frequency-matched cancer-free controls, we genotyped two common polymorphisms in the MKK4 promoter region (–1304T>G and –1044A>T) with the Taqman assay, and we found that compared with the most common –1304TT genotype, carriers of –1304G variant genotypes had a decreased risk of lung cancer [odds ratio (OR) = 0.74; 95% confidence interval (CI) = 0.61–0.90 for TG, and OR = 0.62; 95% CI = 0.41–0.94 for GG] in an allele dose–response manner (adjusted Ptrend = 0.0005). Further stratification analysis showed that the protective role of the –1304G variant allele was more evident in low or normal body mass index (BMI) but restrained in the overweighters and that the –1304G variant genotypes interacted with BMI in reducing cancer risk (adjusted Pinteraction = 0.003). Moreover, the luciferase assay showed that the G allele in the promoter significantly increased the transcription activity of the MKK4 gene in vitro and that the MKK4 protein expression levels of the G variant carriers was significantly higher in tumor tissues than those of the –1304TT genotype. However, no significant association was observed between the –1044A>T polymorphism and risk of lung cancer. Our data suggest that the functional –1304G variant in the MKK4 promoter contributes to a decreased risk of lung cancer by increasing the promoter activity and that the G variant may be a marker for susceptibility to lung cancer.

  O Wang , R. D Kilpatrick , C. W Critchlow , X Ling , B. D Bradbury , D. T Gilbertson , A. J Collins , K. J Rothman and J. F. Acquavella

Background and objectives: Observational studies relating epoetin alfa (EPO) dose and mortality frequently use analytic methods that do not control time-dependent confounding by indication (CBI). The relationship between EPO dose and 1-year mortality, adjusting for the effects of time-dependent CBI, was examined using a marginal structural model.

Design, setting, participants, & measurements: This retrospective cohort study included 27,791 hemodialysis patients between July 2000 and June 2002. Patients were grouped at successive 2-wk intervals into a zero-dose category or four nonzero-dose categories. Ordinal regression was used to calculate inverse probability of treatment weights of patients receiving their own dose level given their covariate and treatment history. Three treatment models with an increasing number of treatment predictors were evaluated to assess the effect of model specification. A small number of excessively large patient weights were truncated. Relative hazards for higher-dose groups compared with the lowest nonzero-dose group varied by treatment model specification and by level of weight truncation.

Results: Results differed appreciably between the simplest treatment model, which incorporated only hemoglobin and EPO dosing history with 2% weight truncation (hazard ratio: 1.51; 95% confidence interval: 1.09, 1.89 for highest-dose patients), and the most comprehensive treatment model with 1% weight truncation (hazard ratio: 0.98; 95% confidence interval: 0.76, 1.74).

Conclusions: There is appreciable CBI at higher EPO doses, and EPO dose was not associated with increased mortality in marginal structural model analyses that more completely addressed this confounding.

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