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Articles by G Bobe
Total Records ( 3 ) for G Bobe
  C Zhao , I Ivanov , E. R Dougherty , T. J Hartman , E Lanza , G Bobe , N. H Colburn , J. R Lupton , L. A Davidson and R. S. Chapkin
 

We have developed novel molecular methods using a stool sample, which contains intact sloughed colon cells, to quantify colonic gene expression profiles. In this study, our goal was to identify diagnostic gene sets (combinations) for the noninvasive classification of different phenotypes. For this purpose, the effects of a legume-enriched, low glycemic index, high fermentable fiber diet was evaluated in subjects with four possible combinations of risk factors, including insulin resistance and a history of adenomatous polyps. In a randomized crossover design controlled feeding study, each participant (a total of 23; 5–12 per group) consumed the experimental diet (1.5 cups of cooked dry beans) and a control diet (isocaloric average American diet) for 4 weeks with a 3-week washout period between diets. Using prior biological knowledge, the complexity of feature selection was reduced to perform an exhaustive search on all allowable feature (gene) sets of size 3, and among these, 27 had (unbiased) error estimates of 0.15 or less. Linear discriminant analysis was successfully used to identify the best single genes and two- to three-gene combinations for distinguishing subjects with insulin resistance, a history of polyps, or exposure to a chemoprotective legume-rich diet. These results support our premise that gene products (RNA) isolated from stool have diagnostic value in terms of assessing colon cancer risk.

  C. E Camalier , M. R Young , G Bobe , C. M Perella , N. H Colburn and G. R. Beck
 

Recent results suggest a paradigm shift from viewing inorganic phosphate as a passive requirement for basic cell functions to an active regulator of cell behavior. We have previously shown that elevated concentrations of phosphate increased cell proliferation and expression of protumorigenic genes such as Fra-1 and osteopontin in a preosteoblast cell line. Therefore, we hypothesized that elevated phosphate concentrations would promote cell transformation in vitro and tumorigenesis in vivo. Supplementation of medium with phosphate increased anchorage-independent transformation and proliferation of BALB/c mouse JB6 epidermal cells, activation of N-ras, ERK1/2, and activator protein-1, and increased gene expression of Fra-1, COX-2, and osteopontin in a dose-dependent manner. These in vitro results led to the hypothesis that varying the levels of dietary inorganic phosphate would alter tumorigenesis in the mouse model of skin carcinogenesis. Female FVB/N mice were treated with 7,12-dimethylbenz(a)anthracene/12-O-tetradecanoylphorbol-13-acetate and fed high- or low-phosphate diets (1.2% versus 0.2% of the diet) for 19 weeks. The high-phosphate diet increased skin papilloma number by ~50% without changing feed intake and body weights. High dietary phosphate increased serum concentrations of phosphate, parathyroid hormone, and osteopontin and decreased serum concentrations of calcium. Thus, we conclude that elevated phosphate promotes cell transformation and skin tumorigenesis partly by increasing the availability of phosphate for activation of N-ras and its downstream targets, which defines reducing dietary phosphate as a novel target for chemoprevention. Cancer Prev Res; 3(3); 359–70

  A. M Gamero , M. R Young , R Mentor Marcel , G Bobe , A. J Scarzello , J Wise and N. H. Colburn
 

Signal transducer and activator of transcription 2 (STAT2) is an essential transcription factor in the type I IFN (IFN-/β) signal transduction pathway and known for its role in mediating antiviral immunity and cell growth inhibition. Unlike other members of the STAT family, IFNs are the only cytokines known to date that can activate STAT2. Given the inflammatory and antiproliferative dual nature of IFNs, we hypothesized that STAT2 prevents inflammation-induced colorectal and skin carcinogenesis by altering the inflammatory immune response. Contrary to our hypothesis, deletion of STAT2 inhibited azoxymethane/dextran sodium sulfate–induced colorectal carcinogenesis as measured by prolonged survival, lower adenoma incidence, smaller polyps, and less chronic inflammation. STAT2 deficiency also inhibited 7,12-dimethylbenz(a)anthracene/12-O-tetradecanoylphorbol-13-acetate–induced skin carcinogenesis as indicated by reduced papilloma multiplicity. A potential mechanism by which STAT2 promotes carcinogenesis is through activation of proinflammatory mediators. Deletion of STAT2 decreased azoxymethane/dextran sodium sulfate–induced expression and release of proinflammatory mediators, such as interleukin-6 and CCL2, and decreased interleukin-6 release from skin carcinoma cells, which then decreased STAT3 activation. Our findings identify STAT2 as a novel contributor to colorectal and skin carcinogenesis that may act to increase the gene expression and secretion of proinflammatory mediators, which in turn activate the oncogenic STAT3 signaling pathway. Cancer Prev Res; 3(4); 495–504. ©2010 AACR.

 
 
 
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