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Inhibition of NOX1 Gene Expression with shRNA in Human Colon Cancer

ABSTRACT: NOX1 gene is member of the NADPH-dependent superoxide producing enzyme family. It generates reactive oxygen species (ROS) in regulated manner in response to growth factors, cytokines and calcium signal. Low levels of ROS play role in many processes including cell proliferation, inflammatory response and mitogenesis. NOX1 over-expression in colon cancer cell lines as well as surgical samples suggests a role in colon cancer. We identified unique target sequences of siRNAs for post-transcriptional silencing of NOX1. Gene specific and scrambled (control) sequence carrying U6 promoter/shRNA cassettes were cloned into GFP expression vector. Stable clones were selected based on NOX1 expression after transient transfection of HT-29 cells. Clone 6A and 6C showed 70-80% decrease in NOX1 expression. The cells were expanded and analyzed further. We measured decreased ROS production, cell proliferation and G1/S block of the cell cycle. HT-29 parental cells, clone SA (scrambled) and clone 6A (gene specific) were utilized to establish xenografts in athymic mice to investigate the effect of NOX1 silencing on tumor growth and gene expression in vivo. Significant decrease was measured in the volume of forming tumors. The stable clones and corresponding xenografts were analyzed on microarray. The microarray data was validated with real-time PCR and western-blot analysis demonstrating the inhibition of genes important in cell cycle regulation and angiogenesis. The results of this study show silencing NOX1 levels of generated ROS decreased, the tumor formation attenuated in vivo suggesting NOX1 may be a therapeutic target for colon cancer. Keywords: gene silencing with shRNA

ORGANISM(S): Homo sapiens

PROVIDER: GSE4561 | GEO | 2007/03/27

SECONDARY ACCESSION(S): PRJNA94485

REPOSITORIES: GEO

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Project description:NOX1 gene is member of the NADPH-dependent superoxide producing enzyme family. It generates reactive oxygen species (ROS) in regulated manner in response to growth factors, cytokines and calcium signal. Low levels of ROS play role in many processes including cell proliferation, inflammatory response and mitogenesis. NOX1 over-expression in colon cancer cell lines as well as surgical samples suggests a role in colon cancer. We identified unique target sequences of siRNAs for post-transcriptional silencing of NOX1. Gene specific and scrambled (control) sequence carrying U6 promoter/shRNA cassettes were cloned into GFP expression vector. Stable clones were selected based on NOX1 expression after transient transfection of HT-29 cells. Clone 6A and 6C showed 70-80% decrease in NOX1 expression. The cells were expanded and analyzed further. We measured decreased ROS production, cell proliferation and G1/S block of the cell cycle. HT-29 parental cells, clone SA (scrambled) and clone 6A (gene specific) were utilized to establish xenografts in athymic mice to investigate the effect of NOX1 silencing on tumor growth and gene expression in vivo. Significant decrease was measured in the volume of forming tumors. The stable clones and corresponding xenografts were analyzed on microarray. The microarray data was validated with real-time PCR and western-blot analysis demonstrating the inhibition of genes important in cell cycle regulation and angiogenesis. The results of this study show silencing NOX1 levels of generated ROS decreased, the tumor formation attenuated in vivo suggesting NOX1 may be a therapeutic target for colon cancer. Experiment Overall Design: We have found that NOX1 over-expression in colon cancer cell lines as well as surgical samples suggests a role in colon cancer. We identified unique target sequences of siRNAs for post-transcriptional silencing of NOX1. Gene specific and scrambled (control) sequences carrying the U6 promoter/shRNA cassettes were cloned into a GFP expression vector. Stable clones were selected based on NOX1 expression after transient transfection of HT-29 cells. HT-29 parental cells, clone SA (scrambled) and clone 6A (gene specific) were utilized to establish xenografts in athymic mice to investigate the effect of NOX1 silencing on tumor growth and gene expression in vivo. A significant decrease was measured in the volume of tumors formed. The stable clones and corresponding xenografts were analyzed on microarray. The microarray data was validated with real-time PCR and western-blot analysis demonstrating the inhibition of genes important in cell cycle regulation and angiogenesis. The results of this study show silencing NOX1 levels of generated ROS decreased, the tumor formation attenuated in vivo suggesting NOX1 may be a therapeutic target for colon cancer.

Project description:Metastasis and drug-resistance are major problems in cancer chemotherapy. The purpose of this work was to analyze the molecular mechanisms underlying the invasive potential of drug-resistant colon carcinoma cells. Cellular models included the parental HT-29 cell line and its drug-resistant derivatives selected after chronic treatment with either 5-fluorouracil (5-FU), methotrexate (MTX), doxorubicin (DOX) or oxaliplatin (OXA). Drug-resistant invasive cells were compared to non invasive cells using cDNA microarray, qRT-PCR, flow cytometry, immunoblots and ELISA. Functional and cellular signaling analyses were undertaken using pharmacological inhibitors, function-blocking antibodies, and silencing by retrovirus-mediated RNA interference. 5-FU- and MTX-resistant HT-29 cells expressing an invasive phenotype in collagen type I and a metastatic behaviour in immunodeficient mice exhibited high expression of the chemokine receptor CXCR4. Macrophage migration inhibitory factor (MIF) was identified as the critical autocrine CXCR4 ligand promoting invasion in drug-resistant colon carcinoma HT-29 cells. Silencing of CXCR4 and impairing the MIF-CXCR4 signaling pathways by ISO-1, pAb FL-115, AMD-3100, mAb 12G5, and BIM-46187 abolished this aggressive phenotype. Induction of CXCR4 is associated with up-regulation of two genes encoding transcription factors previously shown to control CXCR4 expression (HIF-2a and ASCL2) and maintenance of intestinal stem cells (ASCL2). Enhanced CXCR4 expression was detected in liver metastases resected from colon cancer patients treated by the standard FOLFOX regimen. Combination therapies targeting the CXCR4-MIF axis can potentially counteract the emergence of the invasive metastatic behaviour in clonal derivatives of drug-resistant colon cancer cells. Samples: HT-29 cell clones were obtained by limiting dilution from HT-29 subpopulations resistant to methothrexate (HT-29 5M21 cell clone) and or to 5-Fluoro-uracil (HT-29 5F7 and HT-29 5F31). Samples were provided by Dr. T Lesuffleur. Xenografts: HT-29 5M21, HT-29 5F7, and HT-29 5F31 xenografts were obtained by a first subcutaneous inoculation of cells in Nude mice and then fragments of subcutaneous tumors were reimplantated in SCID mice. First experiment of microarrays: HT-29 5M21 and HT-29 5F7 cells (that are invasive in in vitro assays on type I collagen) were compared to HT-29 5F31 cells (that are not invasive in vitro on type I collagen). Samples were co-hybridized on Agilent Human 44K GEP arrays (respectively 5F31 vs 5M21, 5F31 vs 5F7, 5M21 vs 5F31 and 5F7 vs 5F31). Second experiment of microarrays: HT-29 5M21 and HT-29 5F7 xenografts (that develop metastases in immuno-deficient mice lungs) were compared to HT-29 5F31 xenografts (that do not develop metastases in immuno-deficient mice lungs). Samples were consequently co-hybridized on human and mouse 4x44K GEP arrays (respectively AG41_5F31-5M21-138869, AG39_5F31-5F7-138867, AG42_5M21-5F31-138870 and AG40_5F7-5F31-138868 for human microarrays; 5M21_5F31_27033_4, 5F31_5M21_27033_3, 5F7_5F31_27033_2 and 5F31_5F7_27033_1_1 for mouse microarrays).

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Inhibition of NOX1 Gene Expression with shRNA in Human Colon Cancer

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