gw-501516 and Carcinogenesis

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

In previous investigations, we reported that peroxisome proliferator-activated receptor β/δ (PPARβ/δ) activation by GW501516 inhibits proliferation and promotes apoptosis in the undifferentiated C666-1 nasopharyngeal carcinoma (NPC) cells by modulating caspase-dependent apoptotic pathway. In the present study, the mechanism by which GW501516 induces apoptosis was explored from the perspective of microRNA (miRNA) expression. Among the assayed miRNAs that were involved in regulating the expression of antiapoptotic protein Bcl-2, miR-206 was increased significantly and specifically by GW501516 in C666-1 cells at both the in vitro level and at the in vivo xenograft samples. The induction on miR-206 expression caused by GW501516 was capable of being antagonized by the PPARβ/δ antagonist GSK3787 and AMPK antagonist dorsomorphin in C666-1 cells. GW501516's suppression on the growth and apoptosis of C666-1 cells was found to be dependent on the presence of miR-206. miR-206 overexpression resulted in suppressed proliferation and colony formation ability, and further triggered increased apoptosis in C666-1 cells in a caspase-dependent manner. The expression of cleaved caspase 3 and caspase 9, and the ratio of Bax to Bcl-2 were elevated remarkably by miR-206. Consistent with the in vitro result, miR-206 was corroborated to suppress the ectopic NPC xenograft tumorigenesis that derived from the C666-1 cells in BALB/c nu/nu mice. Taken together, the current data demonstrated that miR-206 plays a critical role in the direct apoptosis-promoting effect induced by GW501516 in C666-1 cells. Furthermore, the emphasized tumor-suppressive role of miR-206 in the C666-1 cells indicates that it has the potential to provide a new therapeutic approach for the undifferentiated NPC.

Topics: Animals; Apoptosis; Carcinogenesis; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Gene Expression Regulation, Neoplastic; Heterografts; Humans; Mice; MicroRNAs; Nasopharyngeal Carcinoma; PPAR delta; PPAR-beta; Proto-Oncogene Proteins c-bcl-2; Thiazoles

Peroxisome proliferator-activated receptor (PPAR) δ is a promising therapeutic target in metabolic and inflammatory disorders. However, its role in oncogenesis is controversial, and its therapeutic potential remains to be determined. In our study, we show that ligand-activated PPARδ forms a complex with the proto-oncogene product c-Myc. The interaction of PPARδ with c-Myc affected the transcriptional activity of c-Myc and the expression of its target genes. The PPARδ-dependent regulation of c-Myc activity was associated with decreased tumorigenicity in breast cancer cells. Administration of the PPARδ ligand GW501516 inhibited tumor growth in xenograft model mice bearing MDA-MB-231 cells stably expressing wild-type PPARδ, but not those expressing dominant-negative PPARδ, by interfering with c-Myc function through protein-protein interaction. Our results indicating that PPARδ forms an antitumorigenic complex with c-Myc in the presence of ligand suggest a potential role of PPARδ in breast cancer development.

Topics: A549 Cells; Animals; Breast Neoplasms; Carcinogenesis; Cell Line; Cell Line, Tumor; Cell Transformation, Neoplastic; Gene Expression Regulation, Neoplastic; HEK293 Cells; HeLa Cells; Humans; Ligands; MCF-7 Cells; PC12 Cells; PPAR delta; Proto-Oncogene Mas; Proto-Oncogene Proteins c-myc; Rats; RNA, Small Interfering; Thiazoles

The peroxisome proliferator-activated receptor-δ (PPARδ) regulates a multitude of physiological processes associated with glucose and lipid metabolism, inflammation, and proliferation. One or more of these processes are potential risk factors for the ability of PPARδ agonists to promote tumorigenesis in the mammary gland. In this study, we describe a new transgenic mouse model in which activation of PPARδ in the mammary epithelium by endogenous or synthetic ligands resulted in progressive histopathologic changes that culminated in the appearance of estrogen receptor- and progesterone receptor-positive and ErbB2-negative infiltrating ductal carcinomas. Multiparous mice presented with mammary carcinomas after a latency of 12 months, and administration of the PPARδ ligand GW501516 reduced tumor latency to 5 months. Histopathologic changes occurred concurrently with an increase in an inflammatory, invasive, metabolic, and proliferative gene signature, including expression of the trophoblast gene, Plac1, beginning 1 week after GW501516 treatment, and remained elevated throughout tumorigenesis. The appearance of malignant changes correlated with a pronounced increase in phosphatidylcholine and lysophosphatidic acid metabolites, which coincided with activation of Akt and mTOR signaling that were attenuated by treatment with the mTOR inhibitor everolimus. Our findings are the first to show a direct role of PPARδ in the pathogenesis of mammary tumorigenesis, and suggest a rationale for therapeutic approaches to prevent and treat this disease.

Topics: Animals; Carcinogenesis; Carcinoma, Ductal; Epithelium; Female; Gene Expression; Genes, erbB-2; Inflammation; Inflammatory Breast Neoplasms; Mammary Neoplasms, Experimental; Metabolomics; Mice; Mice, Transgenic; Phenotype; PPAR delta; Proto-Oncogene Proteins c-akt; Receptors, Estrogen; Receptors, Progesterone; Thiazoles; TOR Serine-Threonine Kinases