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Deficiency in the 15 kDa Selenoprotein Inhibits Tumorigenicity and Metastasis of Colon Cancer Cells

ABSTRACT: 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 –independent 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE20390 | GEO | 2010/07/07

SECONDARY ACCESSION(S): PRJNA125515

REPOSITORIES: GEO

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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.

Project description:Vascular endothelial growth factor is a multifunctional cytokine playing important roles in angiogenesis, tumor progression and metastasis. Alternative splicing results in the production of several different isoforms of VEGF. We have previously generated human breast cancer cells overexpressing VEGF165 or VEGF189 isoforms (referred to as the V165 and V189 clones, respectively) and showed that VEGF189-transfected cells were less tumorigenic. In this study, we used bioluminescence imaging to analyze the metastasis capacity of breast cancer cell lines (MDA-MB-321) overexpressing VEGF isoforms in nude mice. V165, V189 and control cV clones were transfected with a luciferase plasmid to generate bioluminescent clones (the V165-B, V189-B and cV clones, respectively). These clones were then injected into the left heart ventricle of nude mice. Analysis of the location of metastases shows that V189-B cells induced fewer metastases in lung and bone than V165-B and cV-B cells. Moreover, there was a delay on metastasis appearance in mice receiving VEGF V189-B clone, consistent with increase survival in these mice. We investigated the possible mechanisms underlying these effects and found that VEGF189 increased adhesion and decreased cell invasion and survival in vitro. In the other side, transcriptomic analyses shown expression of genes, implicated in breast cancer and metastatic dissemination, in VEGF165 overexpressing cells. After in silico analyses of genes differentially expressed between V189 and V165 cells,we used Q-PCR assays to quantify mRNA levels of some gene of interest in 120 breast tumors from patients with or without metastasis and/or specially lung metastasis. We found that genes have prognostical significance and /or showed an influence on relapse-free survival. These data provide the first evidence that different VEGF isoforms have different effects on breast cancer cell line invasion and colonization. Human MDA-MB-231 breast cancer cells were used to generate stable transfected clones overexpressing VEGF165 isoform, VEGF189 isoform, or control vector (referred to as 42ctl8, 13ctl3 and PCIctl3, respectively). Analysis of the metastasis capacity of these clones in nude mice.

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Deficiency in the 15 kDa Selenoprotein Inhibits Tumorigenicity and Metastasis of Colon Cancer Cells

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