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Knockout of the 15 kDa selenoprotein protects against chemically-induced aberrant crypt formation in mice.

ABSTRACT: Evidence suggests that selenium has cancer preventive properties that are largely mediated through selenoproteins. Our previous observations demonstrated that targeted down-regulation of the 15 kDa selenoprotein (Sep15) in murine colon cancer cells resulted in the reversal of the cancer phenotype. The present study investigated the effect of Sep15 knockout in mice using a chemically-induced colon cancer model. Homozygous Sep15 knockout mice, and wild type littermate controls were given four weekly subcutaneous injections of azoxymethane (10 mg/kg). Sep15 knockout mice developed significantly (p<0.001) fewer aberrant crypt foci than controls demonstrating that loss of Sep15 protects against aberrant crypt foci formation. Dietary selenium above adequate levels did not significantly affect aberrant crypt foci formation in Sep15 knockout mice. To investigate molecular targets affected by loss of Sep15, gene expression patterns in colonic mucosal cells of knockout and wild type mice were examined using microarray analysis. Subsequent analyses verified that guanylate binding protein-1 (GBP-1) mRNA and protein expression were strongly upregulated in Sep15 knockout mice. GBP-1, which is expressed in response to interferon-?, is considered to be an activation marker during inflammatory diseases, and up-regulation of GBP-1 in humans has been associated with a highly significant, increased five-year survival rate in colorectal cancer patients. In agreement with these studies, we observed a higher level of interferon-? in plasma of Sep15 knockout mice. Overall, our results demonstrate for the first time, that Sep15 knockout mice are protected against chemically-induced aberrant crypt foci formation and that Sep15 appears to have oncogenic properties in colon carcinogenesis in vivo.

SUBMITTER: Tsuji PA

PROVIDER: S-EPMC3514276 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Knockout of the 15 kDa selenoprotein protects against chemically-induced aberrant crypt formation in mice.

Tsuji Petra A PA Carlson Bradley A BA Naranjo-Suarez Salvador S Yoo Min-Hyuk MH Xu Xue-Ming XM Fomenko Dmitri E DE Gladyshev Vadim N VN Hatfield Dolph L DL Davis Cindy D CD

PloS one 20121204 12

Evidence suggests that selenium has cancer preventive properties that are largely mediated through selenoproteins. Our previous observations demonstrated that targeted down-regulation of the 15 kDa selenoprotein (Sep15) in murine colon cancer cells resulted in the reversal of the cancer phenotype. The present study investigated the effect of Sep15 knockout in mice using a chemically-induced colon cancer model. Homozygous Sep15 knockout mice, and wild type littermate controls were given four week ...[more]

PMID: 23226526

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Project description:Selenium has cancer preventive activity that is mediated, in part, through selenoproteins. The role of the 15 kDa selenoprotein (Sep15) in colon cancer was assessed by preparing and using mouse colon CT26 cells stably transfected with shRNA constructs targeting Sep15. Metabolic 75Se-labeling and Northern and Western blot analyses revealed that more than 90% of Sep15 was knocked down. Growth of the resulting Sep15-deficient CT26 cells was reduced (p<0.01) and cells formed significantly (p<0.001) fewer colonies in soft agar compared to control CT26 cells. Whereas most (14/15) BALB/c mice injected with control cells developed tumors, few (3/30) mice injected with Sep15 knockdown cells developed tumors (p<0.0001). The ability to form pulmonary metastases had similar results. Mice injected with the plasmid-transfected control cells had >250 lung metastases/mouse; however, mice injected with the Sep15 knockdown cells only had 7.8 +/- 5.4 metastases. To investigate molecular targets affected by Sep15 status, gene expression patterns between control and knockdown CT26 cells were compared. Ingenuity Pathways Analysis was used to analyze the 1045 genes that were significantly (p<0.001) affected by Sep15 deficiency. The highest scored biological functions were cancer and cellular growth and proliferation. Consistent with these observations, subsequent analyses revealed a G2/M cell cycle arrest in Sep15 CT26 knockdown cells. In contrast, to CT26 cells Sep15 knockdown in Lewis Lung Carcinoma (LLC1) cells did not affect anchorage-dependent or M-bM-^@M-^Sindependent cell growth. These data suggest tissue specificity in the cancer protective effects of Sep15 knockdown, which are mediated, at least in part, by influencing the cell cycle. mRNA was isolated from plasmid-transfected control and shSep15 knockdown CT26 cells (three replicates of each). Microarray analysis was performed on Affymetrix Mouse 430_2 gene chips. Three arrays were analyzed from different mRNA samples for each construct.

Dataset Information

Knockout of the 15 kDa selenoprotein protects against chemically-induced aberrant crypt formation in mice.

Publications

Knockout of the 15 kDa selenoprotein protects against chemically-induced aberrant crypt formation in mice.

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