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Runx1 is a tumor suppressor gene in the mouse gastrointestinal tract

ABSTRACT: The Runx1 transcription factor plays an important role in tissue homeostasis through its effects on stem/progenitor cell populations and differentiation. The effect of Runx1 on epithelial differentiation of the secretory cell lineage of the colon was recently demonstrated. This study aimed to examine the role of Runx1 in tumor development in epithelial cells of the gastrointestinal tract. Conditional knockout mice were generated that lacked Runx1 expression in epithelial cells of the GI tract. These mice were crossed onto the ApcMin background, sacrificed, and their intestinal tumor phenotypes were compared with ApcMin Runx1 wildtype control mice. Apc-wildtype Runx1-mutant mice were also examined for tumor development. Colons from Runx1 knockout and wildtype mice were used for genome-wide mRNA expression analyses followed by gene-specific quantitative RT-PCR of whole colon and colon epithelium, to identify Runx1 target genes. Runx1 deficiency in intestinal epithelial cells significantly enhanced tumorigenesis in ApcMin mice. Notably, epithelial Runx1 deficiency in Apc-wildtype mice was sufficient to cause tumor development. Absence of Runx1 was associated with global changes in expression of genes involved in inflammation and intestinal metabolism, and with gene sets indicative of metastatic phenotype and poor prognosis. Gene-specific analysis of Runx1 deficient colon epithelium revealed increased expression of genes linked to an expansion of the stem/progenitor cell population. These results identify Runx1 as a novel tumor suppressor gene for gastrointestinal tumors and support a role for Runx1 in maintaining the balance between the intestinal stem/progenitor cell population and epithelial differentiation of the GI tract.

ORGANISM(S): Mus musculus

PROVIDER: GSE34292 | GEO | 2012/09/13

SECONDARY ACCESSION(S): PRJNA149943

REPOSITORIES: GEO

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Project description:The Runx1 transcription factor plays an important role in tissue homeostasis through its effects on stem/progenitor cell populations and differentiation. The effect of Runx1 on epithelial differentiation of the secretory cell lineage of the colon was recently demonstrated. This study aimed to examine the role of Runx1 in tumor development in epithelial cells of the gastrointestinal tract. Conditional knockout mice were generated that lacked Runx1 expression in epithelial cells of the GI tract. These mice were crossed onto the ApcMin background, sacrificed, and their intestinal tumor phenotypes were compared with ApcMin Runx1 wildtype control mice. Apc-wildtype Runx1-mutant mice were also examined for tumor development. Colons from Runx1 knockout and wildtype mice were used for genome-wide mRNA expression analyses followed by gene-specific quantitative RT-PCR of whole colon and colon epithelium, to identify Runx1 target genes. Runx1 deficiency in intestinal epithelial cells significantly enhanced tumorigenesis in ApcMin mice. Notably, epithelial Runx1 deficiency in Apc-wildtype mice was sufficient to cause tumor development. Absence of Runx1 was associated with global changes in expression of genes involved in inflammation and intestinal metabolism, and with gene sets indicative of metastatic phenotype and poor prognosis. Gene-specific analysis of Runx1 deficient colon epithelium revealed increased expression of genes linked to an expansion of the stem/progenitor cell population. These results identify Runx1 as a novel tumor suppressor gene for gastrointestinal tumors and support a role for Runx1 in maintaining the balance between the intestinal stem/progenitor cell population and epithelial differentiation of the GI tract. A total of 8 colon tissue RNA samples were analyzed, comprising 4 colon samples from wild-type mice (Villin-Cre negative / Runx1-floxed) and 4 colon samples from mice that lack epithelial expression of Runx1 (Villin-Cre positive/Runx1-floxed).

Project description:To identify the precise molecular mechanisms that could contribute to the increase in colon carcinogenesis, microarray gene expression analysis was performed on colon RNA isolated from 5-week-old VhlF/F and VhlΔIE, VhlΔIE/Apcmin/+ and VhlF/F/Apcmin/+ mice. Hypoxia-inducible factor (HIF) is a key modulator of the transcriptional response to hypoxia and is increased in colon cancer. However, the role of HIF in colon carcinogenesis in vivo remains unclear. Intestinal epithelium-specific disruption of the von Hippel-Lindau tumor suppressor protein (VHL) resulted in constitutive HIF signaling, and increased HIF expression augmented colon tumorigenesis in the Apcmin/+ intestinal tumor model. Intestine-specific disruption of Vhl increased colon tumor multiplicity and progression from adenomas to carcinomas. These effects were ameliorated in mice with double disruption of Vhl and Hif-2α. Activation of HIF signaling resulted in increased cell survival in normal colon tissue, however tumor apoptosis was not affected. Interestingly, a robust activation of cyclin D1 was observed in tumors of Apcmin/+ mice in which HIF-2α was activated in the intestine. Consistent with this result, BrdU incorporation indicated that cellular proliferation was increased in colon tumors following HIF activation. Further analysis demonstrated that dysregulation of the intestinal iron absorption transporter divalent metal transporter-1 (DMT-1) was a critical event in HIF-2α-mediated colon carcinogenesis. These data provide a mechanistic basis for the widely reported link between iron accumulation and colon cancer risk. Together, our findings demonstrate that a chronic increase in HIF-2α in the colon initiates pro-tumorigenic signaling which may have important implications in developing preventive and therapeutic strategies for colon cancer. Global gene expression profiling in colon RNAs isolated from 5-week-old VhlF/F (n=4, Shah 001), VhlF/F/Apcmin/+(n=3, Shah 003), VhlΔIE (n=3, Shah 002) and VhlΔIE/Apcmin/+ mice (n=5, Shah 004).

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Runx1 is a tumor suppressor gene in the mouse gastrointestinal tract

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