Suppression of Membranous LRP5 Recycling, Wnt/ß-Catenin Signaling, and Colon Carcinogenesis by 15-LOX-1 Peroxidation of Linoleic Acid in PI3P.

APC mutation activation of Wnt/ß-catenin drives initiation of colorectal carcinogenesis (CRC). Additional factors potentiate ß-catenin activation to promote CRC. Western diets are enriched in linoleic acid (LA); LA-enriched diets promote chemically induced CRC in rodents. 15-Lipoxygenase-1 (15-LOX-1), the main LA-metabolizing enzyme, is transcriptionally silenced during CRC. Whether LA and 15-LOX-1 affect Wnt/ß-catenin signaling is unclear. We report that high dietary LA promotes CRC in mice treated with azoxymethane or with an intestinally targeted Apc mutation (ApcΔ580) by upregulating Wnt receptor LRP5 protein expression and ß-catenin activation. 15-LOX-1 transgenic expression in mouse intestinal epithelial cells suppresses LRP5 protein expression, ß-catenin activation, and CRC. 15-LOX-1 peroxidation of LA in phosphatidylinositol-3-phosphates (PI3P_LA) leads to PI3P_13-HODE formation, which decreases PI3P binding to SNX17 and LRP5 and inhibits LRP5 recycling from endosomes to the plasma membrane, thereby increasing LRP5 lysosomal degradation. This regulatory mechanism of LRP5/Wnt/ß-catenin signaling could be therapeutically targeted to suppress CRC.

PPARD and Interferon Gamma Promote Transformation of Gastric Progenitor Cells and Tumorigenesis in Mice.

BACKGROUND & AIMS: The peroxisome proliferator-activated receptor delta (PPARD) regulates cell metabolism, proliferation, and inflammation and has been associated with gastric and other cancers. Villin-positive epithelial cells are a small population of quiescent gastric progenitor cells. We expressed PPARD from a villin promoter to investigate the role of these cells and PPARD in development of gastric cancer. METHODS: We analyzed gastric tissues from mice that express the Ppard (PPARD1 and PPARD2 mice) from a villin promoter, and mice that did not carry this transgene (controls), by histology and immunohistochemistry. We performed cell lineage-tracing experiments and analyzed the microbiomes, chemokine and cytokine production, and immune cells and transcriptomes of stomachs of these mice. We also performed immunohistochemical analysis of PPARD levels in 2 sets of human gastric tissue microarrays. RESULTS: Thirty-eight percent of PPARD mice developed spontaneous, invasive gastric adenocarcinomas, with severe chronic inflammation. Levels of PPARD were increased in human gastric cancer tissues, compared with nontumor tissues, and associated with gastric cancer stage and grade. We found an inverse correlation between level of PPARD in tumor tissue and patient survival time. Gastric microbiomes from PPARD and control mice did not differ significantly. Lineage-tracing experiments identified villin-expressing gastric progenitor cells (VGPCs) as the origin of gastric tumors in PPARD mice. In these mice, PPARD up-regulated CCL20 and CXCL1, which increased infiltration of the gastric mucosa by immune cells. Immune cell production of inflammatory cytokines promoted chronic gastric inflammation and expansion and transformation of VGPCs, leading to tumorigenesis. We identified a positive-feedback loop between PPARD and interferon gamma signaling that sustained gastric inflammation to induce VGPC transformation and gastric carcinogenesis. CONCLUSIONS: We found PPARD overexpression in VPGCs to result in inflammation, dysplasia, and tumor formation. PPARD and VGPCs might be therapeutic targets for stomach cancer.

Pleiotropic Effects of PPARD Accelerate Colorectal Tumorigenesis, Progression, and Invasion.

APC mutations activate aberrant ß-catenin signaling to drive initiation of colorectal cancer; however, colorectal cancer progression requires additional molecular mechanisms. PPAR-delta (PPARD), a downstream target of ß-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 ß-catenin activation and colorectal cancer. In this study, we used mouse models of PPARD overexpression or deletion combined with APC mutation (ApcΔ580 ) in intestinal epithelial cells (IEC) to elucidate the contributions of PPARD in colorectal cancer. Overexpression or deletion of PPARD in IEC augmented or suppressed ß-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/ß-catenin signaling and suppressed organoid self-renewal. Treatment with PPARD agonist GW501516 enhanced colorectal cancer tumorigenesis in ApcΔ580 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, PDGFRß, 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.

Hepatitis B virus X protein promotes CREB-mediated activation of miR-3188 and Notch signaling in hepatocellular carcinoma.

Familiar clustering of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) has been frequently reported. However, limited information is available about the underlying molecular mechanisms in HBV-related HCC patients with family history of HCC. In our previous study, Agilent miRNA Base 16.0 microarray showed miRNA profiles of the plasma of HBV-related HCC patients who had a family history of HCC. This study aims to explore the expression, function, and mechanisms of miR-3188 in HCC that might provide novel insights into the role of family history on the risk of HCC. The expression levels of miR-3188 were markedly overexpressed in HCC tissues, HBV transgenic mice, and HepG2.215 cells. We knocked out miR-3188 in HCC cell lines using the CRISPR/Cas9 system, and demonstrated that miR-3188 knockout (KO) suppressed cell growth, migration, and invasion, and inhibited xenografts tumor growth in nude mice. Next, we determined that miR-3188 KO exerts antitumor functions by directly repressing ZHX2. It has been reported that HBV X protein (HBx) plays a critical role in HBV-related HCC, promoting CREB-mediated activation of miR-3188 and activation of Notch signaling through repressing ZHX2. Finally, we verified that ZHX2 functions as a transcriptional repressor to Notch1 via interaction with NF-YA. Our data demonstrate that the HBx-miR-3188-ZHX2-Notch1 signaling pathway plays an important role in the pathogenesis and progression of HBV-related HCC with family history of HCC. These findings have important implications for identifying new therapeutic targets in HBV-related HCC.