gw-501516 and Colorectal-Neoplasms

As a nuclear receptor, peroxisome proliferator-activated receptor-δ (PPARδ) plays a critical role in regulating inflammation and cancer, while it is still unclear the mechanism of PPARδ agonist GW501516 on colitis-associated colorectal cancer. Here we found that GW501516 significantly enhanced colitis-associated colorectal cancer in AOM/DSS-induced mice. In addition, PPARδ agonist GW501516 enhanced pro-inflammatory gene expressions (COX-2, IL-6, IL-8 and MCP-1) in inflamed colon. Further analysis showed that GW501516 increased the expressions of Glut1 and SLC1A5 in colon cancer cells as well as AOM/DSS-induced colorectal tumors. These findings revealed a new mechanism of PPARδ agonist GW501516-mediated colitis-associated colorectal cancer.

Topics: Animals; Carcinogenesis; Cell Line, Tumor; Colitis; Colorectal Neoplasms; Humans; Male; Mice; Mice, Inbred C57BL; PPAR delta; Thiazoles

The nuclear hormone receptor peroxisome proliferator-activated receptor delta (PPARδ) is a ligand-dependent transcription factor involved in fatty acid metabolism, obesity, wound healing, inflammation, and cancer. Although PPARδ has been shown to promote intestinal adenoma formation and growth, the molecular mechanisms underlying the contribution of PPARδ to colorectal cancer remain unclear. Here, we demonstrate that activation of PPARδ induces expansion of colonic cancer stem cells (CSC) and promotes colorectal cancer liver metastasis by binding to the Nanog promoter and enhancing Nanog expression. Moreover, PPARδ mediated the effect of a high-fat diet in promoting liver metastasis and induction of colonic CSC expansion. Our findings uncover a novel role of dietary fats in colorectal cancer metastasis and reveal novel mechanisms underlying PPARδ-mediated induction of CSCs and those responsible for the contribution of dietary fats to colorectal cancer progression. These findings may provide a rationale for developing PPARδ antagonists to therapeutically target CSCs in colorectal cancer. SIGNIFICANCE: These findings show that PPARδ contributes to colorectal cancer metastasis by expanding the CSC population, indicating that antagonists that target PPARδ may be beneficial in treating colorectal cancer.

Topics: Animals; Colorectal Neoplasms; Diet, High-Fat; Dietary Fats; HCT116 Cells; Humans; Liver Neoplasms, Experimental; Male; Mice, Inbred NOD; Mice, Mutant Strains; Nanog Homeobox Protein; Neoplastic Stem Cells; PPAR delta; Promoter Regions, Genetic; Thiazoles; Xenograft Model Antitumor Assays

Peroxisome proliferator-activated receptor γ (PPARγ) may serve as a useful target for drug development in non-diabetic diseases. However, some colorectal cancer cells are resistant to PPARγ agonists by mechanisms that are poorly understood. Here, we provide the first evidence that elevated PPARδ expression and/or activation of PPARδ antagonize the ability of PPARγ to induce colorectal carcinoma cell death. More importantly, the opposing effects of PPARδ and PPARγ in regulating programmed cell death are mediated by survivin and caspase-3. We found that activation of PPARγ results in decreased survivin expression and increased caspase-3 activity, whereas activation of PPARδ counteracts these effects. Our findings suggest that PPARδ and PPARγ coordinately regulate cancer cell fate by controlling the balance between the cell death and survival and demonstrate that inhibition of PPARδ can reprogram PPARγ ligand-resistant cells to respond to PPARγ agonists.

Topics: Apoptosis; Caspase 3; Cell Line, Tumor; Cell Survival; Colorectal Neoplasms; DNA Fragmentation; Gene Expression; Gene Expression Regulation, Neoplastic; Gene Knockout Techniques; Humans; Inhibitor of Apoptosis Proteins; Oxazoles; PPAR delta; PPAR gamma; Survivin; Thiazoles; Tyrosine

Peroxisome-proliferator-activated receptors (PPARs) are nuclear receptors for fatty acids and their derivatives. PPAR subtypes PPARγ and PPARβ/δ are suspected to modulate cancer development in the colon, but their exact role is still discussed controversially.. The present study investigated the impact of PPARγ and PPARβ/δ on vascular endothelial growth factor (VEGF) and cyclooxygenase 2 (COX-2) expressions induced by synthetic and physiological agonists in the colorectal tumor cell lines SW480 and HT29 using reporter gene assays, qRT-PCR and ELISA.. Activation of both PPARγ and PPARβ/δ induced expression of VEGF mRNA and protein in a PPAR-dependent way. The PPARγ agonists ciglitazone and PGJ(2) were the most effective inducers with up to ninefold and threefold increases in VEGF mRNA in SW480 and HT29 cultures, respectively. VEGF secretion was doubled in both cell lines. The PPARβ/δ agonists GW501516 and PGI(2) caused stimulations of only 1.5-fold in both cell lines. In addition, all PPAR agonists induced COX-2 mRNA and secretion of the COX-2 product PGE(2) in HT29 cells. However, this effect was not blocked by knock-down of PPAR expression nor was it essential for VEGF expression as shown by the lack of effect of the COX-2 inhibitor SC236.. In summary, our results identify both PPARγ and PPARβ/δ as an alternative COX-independent mechanism of VEGF induction in colorectal tumor cells.

Topics: Cell Line, Tumor; Colorectal Neoplasms; Cyclooxygenase 2; Humans; Peroxisome Proliferator-Activated Receptors; PPAR delta; PPAR gamma; PPAR-beta; RNA, Messenger; Thiazoles; Thiazolidinediones; Vascular Endothelial Growth Factor A