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Intestinal-specific activatable Myb initiates colon tumorigenesis in mice.

ABSTRACT: Transcription factor Myb is overexpressed in most colorectal cancers (CRC). Patients with CRC expressing the highest Myb are more likely to relapse. We previously showed that mono-allelic loss of Myb in an Adenomatous polyposis coli (APC)-driven CRC mouse model (Apc(Min/+)) significantly improves survival. Here we directly investigated the association of Myb with poor prognosis and how Myb co-operates with tumor suppressor genes (TSGs) (Apc) and cell cycle regulator, p27. Here we generated the first intestinal-specific, inducible transgenic model; a MybER transgene encoding a tamoxifen-inducible fusion protein between Myb and the estrogen receptor-? ligand-binding domain driven by the intestinal-specific promoter, Gpa33. This was to mimic human CRC with constitutive Myb activity in a highly tractable mouse model. We confirmed that the transgene was faithfully expressed and inducible in intestinal stem cells (ISCs) before embarking on carcinogenesis studies. Activation of the MybER did not change colon homeostasis unless one p27 allele was lost. We then established that MybER activation during CRC initiation using a pro-carcinogen treatment, azoxymethane (AOM), augmented most measured aspects of ISC gene expression and function and accelerated tumorigenesis in mice. CRC-associated symptoms of patients including intestinal bleeding and anaemia were faithfully mimicked in AOM-treated MybER transgenic mice and implicated hypoxia and vessel leakage identifying an additional pathogenic role for Myb. Collectively, the results suggest that Myb expands the ISC pool within which CRC is initiated while co-operating with TSG loss. Myb further exacerbates CRC pathology partly explaining why high MYB is a predictor of worse patient outcome.

SUBMITTER: Malaterre J

PROVIDER: S-EPMC4867492 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Intestinal-specific activatable Myb initiates colon tumorigenesis in mice.

Malaterre J J Pereira L L Putoczki T T Millen R R Paquet-Fifield S S Germann M M Liu J J Cheasley D D Sampurno S S Stacker S A SA Achen M G MG Ward R L RL Waring P P Mantamadiotis T T Ernst M M Ramsay R G RG

Oncogene 20150824 19

Transcription factor Myb is overexpressed in most colorectal cancers (CRC). Patients with CRC expressing the highest Myb are more likely to relapse. We previously showed that mono-allelic loss of Myb in an Adenomatous polyposis coli (APC)-driven CRC mouse model (Apc(Min/+)) significantly improves survival. Here we directly investigated the association of Myb with poor prognosis and how Myb co-operates with tumor suppressor genes (TSGs) (Apc) and cell cycle regulator, p27. Here we generated the f ...[more]

PMID: 26300002

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Project description:Preclinical and clinical studies suggest that 5-lipoxygenase (5-LOX), such as COX-2, is a potential target for colon cancer inhibition and, in part, contributes to cardiovascular side effects associated with COX-2 inhibitors. Experiments were designed to assess the chemopreventive effects of a novel dual 5-LOX/COX inhibitor, licofelone {[6-(4-chlorophenyl)-2,2-dimethyl-7-phenyl-2,3-dihydro-1H-pyrrolizin-5-yl] acetic acid}, in APC(Min/+) mouse intestinal tumorigenesis. Six-week-old male and female APC(Min/+) mice (n = 10 per group) were fed with control American Institute of Nutrition-76A diet or diets containing 150 or 300 ppm licofelone for 14 weeks (?100 days), and intestinal tumors were evaluated for tumor multiplicity and size. Licofelone significantly inhibited total intestinal tumor multiplicity and size in a dose-dependent manner (P < 0.0001; mean tumors for 0, 150, and 300 ppm: 48.8, 17, and 8, respectively, in male mice; and 34.3, 8.8, and 5.5, respectively, in female mice). Licofelone at high dose showed more than 83% (P < 0.0001) tumor inhibition in both genders of mice. One hundred and fifty and 300 ppm licofelone resulted in 86% to 97% inhibition of polyps having size greater than 2 mm. One hundred and fifty and 300 ppm licofelone caused more than 72% and 100% inhibition of colonic tumors, respectively. Importantly, in mice fed with licofelone, tumors showed significantly reduced proliferating cell nuclear antigen expression (70%, P < 0.0001), increased terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells (75%, P < 0.0001), and there was dose-dependent suppression of serum triglycerides (71%-83%, P < 0.0001), decreased inflammatory cytokines; and decreased COX and 5-LOX activities (57%-64%, P < 0.0001). Also, compared with 300 ppm celecoxib, 300 ppm licofelone provided better efficacy in suppressing tumor growth. These observations show that a novel dual 5-LOX/COX inhibitor dramatically suppresses small intestinal and colonic tumor formation in APC(Min/+) mice.

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Intestinal-specific activatable Myb initiates colon tumorigenesis in mice.

Publications

Intestinal-specific activatable Myb initiates colon tumorigenesis in mice.

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