Pleiotropic Effects of PPARD Accelerate Colorectal Tumorigenesis, Progression, and Invasion.
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ABSTRACT: APC mutations activate aberrant ?-catenin signaling to drive initiation of colorectal cancer; however, colorectal cancer progression requires additional molecular mechanisms. PPAR-delta (PPARD), a downstream target of ?-catenin, is upregulated in colorectal cancer. However, promotion of intestinal tumorigenesis following deletion of PPARD in Apcmin mice has raised questions about the effects of PPARD on aberrant ?-catenin activation and colorectal cancer. In this study, we used mouse models of PPARD overexpression or deletion combined with APC mutation (Apc?580 ) in intestinal epithelial cells (IEC) to elucidate the contributions of PPARD in colorectal cancer. Overexpression or deletion of PPARD in IEC augmented or suppressed ?-catenin activation via up- or downregulation of BMP7/TAK1 signaling and strongly promoted or suppressed colorectal cancer, respectively. Depletion of PPARD in human colorectal cancer organoid cells inhibited BMP7/?-catenin signaling and suppressed organoid self-renewal. Treatment with PPARD agonist GW501516 enhanced colorectal cancer tumorigenesis in Apc?580 mice, whereas treatment with PPARD antagonist GSK3787 suppressed tumorigenesis. PPARD expression was significantly higher in human colorectal cancer-invasive fronts versus their paired tumor centers and adenomas. Reverse-phase protein microarray and validation studies identified PPARD-mediated upregulation of other proinvasive pathways: connexin 43, PDGFR?, AKT1, EIF4G1, and CDK1. Our data demonstrate that PPARD strongly potentiates multiple tumorigenic pathways to promote colorectal cancer progression and invasiveness. SIGNIFICANCE: These findings address long-standing, important, and unresolved questions related to the potential role of PPARD in APC mutation-dependent colorectal tumorigenesis by showing PPARD activation enhances APC mutation-dependent tumorigenesis.
SUBMITTER: Liu Y
PROVIDER: S-EPMC6397663 | biostudies-literature | 2019 Mar
REPOSITORIES: biostudies-literature
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