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VHL Status Influences Phenotype of Liver Cancers Arising from PTEN Loss

ABSTRACT: Background: PTEN loss contributes to the development of many cancers and is associated with both hepatocellular carcinoma and cholangiocarcinoma. The pathogenesis of these malignancies is unclear, but they are speculated to arise from common cellular origins. We explored the influence of secondary effects, like hypoxia signaling, through co-deletion of Pten and Vhl in a murine model.Methods: We used a CreER-linked keratin 18 mouse model to conditionally delete Pten, Vhl or both, evaluating the resultant tumors by histology and gene expression microarray. A cohort of human cholangiocarcinoma samples was evaluated for relationships between HIF-1a expression and clinical outcomes.Results: Both Pten deletion genotypes developed liver tumors, but with differing phenotypes. Pten deletion alone led to large, invasive tumors with widespread hepatosteatosis. Co-deletion of Pten and Vhl resulted in low tumor burden and reduced steatosis. Microarray analysis divided mouse tumors’ respective genotypes by gene expression. This gene expression profile grouped a human tumor cohort according to histologic type with the Pten deletion signature aligning with hepatocellular carcinoma, whereas the Pten; Vhl deletion signature associated with cholangiocarcinomas. In a human cholangiocarcinoma cohort, we observed correlation between HIF-1a expression and overall survival.Conclusions: Pten deletion leads to tumor formation and steatosis in mouse livers. Co-deletion of Vhl and Pten resulted in lower tumor burden with gene expression profiling suggesting a switch from hepatocellular expression features to an expression profile more consistent with cholangiocarinoma. A possible relation between HIF-1a expression and increased overall survival in human cholangiocarcinoma suggests that hypoxia signaling influences tumor phenotype.

ORGANISM(S): Mus musculus

PROVIDER: GSE55874 | GEO | 2014/10/31

SECONDARY ACCESSION(S): PRJNA241326

REPOSITORIES: GEO

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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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VHL Status Influences Phenotype of Liver Cancers Arising from PTEN Loss

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