gw9662 and Carcinoma

The peroxisome proliferator-activated receptorγ (PPARγ) is a key regulator of metabolism, proliferation, inflammation and differentiation, and upregulates tumor suppressor genes, such as PTEN, BRCA1 and PPARγ itself. Examination of mammary carcinogenesis in transgenic mice expressing the dominant-negative Pax8PPARγ fusion protein revealed that tumors were estrogen receptorα (ER)-positive and sensitive to the ER antagonist, fulvestrant. Here we evaluated whether administration of an irreversible PPARγ inhibitor in vivo could similarly induce ER expression in otherwise ER-negative mammary tumors following induction of carcinogenesis, and sensitize them to the antitumor effects of fulvestrant. In addition, we wished to determine whether the effect of GW9662 was associated with a PPAR-selective gene expression profile. Mammary carcinogenesis was induced in wild-type FVB mice by treatment with medroxyprogesterone and dimethylbenz(a)anthracene (DMBA) that were subsequently maintained on a diet supplemented with 0.1% GW9662, and tumorigenesis and gene expression profiling of the resulting tumors were determined. Administration of GW9962 resulted in ER+ tumors that were highly sensitive to fulvestrant. Tumors from GW9662-treated animals exhibited reduced expression of a metabolic gene profile indicative of PPARγ inhibition, including PPARγ itself. Additionally, GW9662 upregulated the expression of several genes associated with the transcription, processing, splicing and translation of RNA. This study is the first to show that an irreversible PPARγ inhibitor can mimic a dominant-negative PPARγ transgene to elicit the development of ER-responsive tumors. These findings suggest that it may be possible to pharmacologically influence the responsiveness of tumors to anti-estrogen therapy.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Anilides; Animals; Antineoplastic Agents; Antineoplastic Agents, Hormonal; Carcinogens; Carcinoma; Chemoprevention; Drug Synergism; Estradiol; Estrogen Antagonists; Female; Fulvestrant; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Mammary Neoplasms, Experimental; Mice; Microarray Analysis; Molecular Targeted Therapy; PPAR gamma

Peroxisome proliferator-activated receptor-gamma ligands have preclinical and clinical anticancer activity. Most studies in this area address agonists, with relatively few reports on anticancer effects of peroxisome proliferator-activated receptor-gamma antagonists. Thus, we evaluated the two pure peroxisome proliferator-activated receptor-gamma antagonists, T0070907 and GW9662, on a panel of hematopoietic and epithelial cell lines. The peroxisome proliferator-activated receptor-gamma antagonists and a reference agonist (pioglitazone) were tested in an in-vitro proliferation assay on a panel of seven hematopoietic and nine epithelial cancer cell lines, some of which are chemoresistant. Peroxisome proliferator-activated receptor-gamma expression was measured by immunoblotting, as was the effect of treatment with these agents on peroxisome proliferator-activated receptor-gamma levels. The effect of exogenous interleukin-6, an antiapoptotic cytokine, on growth inhibition was evaluated as well as the apoptotic effects of these drugs. The peroxisome proliferator-activated receptor-gamma antagonists showed significantly greater potency on all cell lines (IC50s of 3.2-29.7 versus 26.5-78.7 micromol/l for pioglitazone) and greater maximum growth inhibition. Peroxisome proliferator-activated receptor-gamma levels did not correlate with growth inhibition in this panel of cell lines. Combinations of peroxisome proliferator-activated receptor-gamma antagonists and the agonist actually showed schedule-dependent increases in growth inhibition. Exogenous interleukin-6 did not induce resistance to these agents. Both the antagonists and the agonist induced apoptosis, but only the former drugs showed caspase dependence. These two peroxisome proliferator-activated receptor-gamma antagonists have significantly more potent in-vitro antiproliferative effects versus hematopoietic and epithelial cancer cell lines. This effect does not correlate with peroxisome proliferator-activated receptor-gamma levels, suggesting alternative mechanisms or other targets of action. These findings support further translational studies to explore the mechanism of action and therapeutic potential of this class of agents.

Topics: Anilides; Antineoplastic Agents; Apoptosis; Benzamides; Carcinoma; Caspase Inhibitors; Caspases; Cell Line, Tumor; Cell Proliferation; Hematologic Neoplasms; Humans; Indicators and Reagents; Interleukin-6; Multiple Myeloma; Pioglitazone; PPAR gamma; Pyridines; Thiazolidinediones

To investigate the effect of 5, 7-dihydroxy-8-nitrochrysin (NOChR) on apoptosis of human gastric carcinoma SGC-7901 cell line.. SGC-7901 cells were cultured in vitro and the inhibitory effect of NOChR on proliferation of SGC-7901 cells was measured by using an MTT assay. NOChR-induced apoptosis rate of SGC-7901 cells was detected using flow cytometry (FCM) with PI staining. DNA ladder bands were observed by DNA agarose gel electrophoresis. The influence of NOChR on the proxisome proliferator-activated receptor-gamma (PPARgamma), Bcl-2 and Bax protein expression of SGC-7901 cells was analyzed by Western blot.. MTT assay showed that NOChR markedly inhibited proliferation of SGC-7901 cells in a dose-dependent manner, and when IC(50) was 4.14 micromol/L, the potency of NOChR was 10 times than that of lead compound, chrysin (ChR, IC(50) was 40.56 micromol/L), and was similar to 5-fluorouracil (5-FU, IC(50) was 4.51 micromol/L). FCM with propidium iodide (PI) staining demonstrated that the apoptosis rates of SGC-7901 cells treated with 1.25, 5.00 and 20.00 micromol/L NOChR for 48 h were 9.8% +/- 0.2%, 36.8% +/- 1.9% and 45.5% +/- 3.5%, respectively, and were significantly higher when treated with 5.00 and 20.00 micromol/L NOChR than that with 20.00 micromol/L ChR (12.9% +/- 1.5%). DNA agarose gel electrophoresis showed that treatment of SGC-7901 cells with 20.00 micromol/L NOChR for 48 h resulted in typical DNA ladder bands of DNA of SGC-7901 cells, which could be eliminated by treating with 10.00 micromol/L GW9662, a blocker of PPARgamma. Western blot analysis revealed that after 24 h of treatment with 20.00 micromol/L NOChR, PPARgamma and Bax protein expression of SGC-7901 cells increased but Bcl-2 expression decreased; however, pre-incubation with 10.00 micromol/L GW9662 could efficiently antagonize and weaken the regulatory effect of 20.00 micromol/L NOChR on Bax and Bcl-2 protein expression of SGC-7901 cells.

Topics: Anilides; Apoptosis; bcl-2-Associated X Protein; Carcinoma; Cell Line, Tumor; Cell Proliferation; Electrophoresis, Agar Gel; Flavonoids; Flow Cytometry; Humans; Nitro Compounds; PPAR gamma; Propidium; Protein Biosynthesis; Proto-Oncogene Proteins c-bcl-2; Stomach Neoplasms; Tetrazolium Salts; Thiazoles