t-0070907 and Colonic-Neoplasms

Although peroxisome proliferator-activated receptor gamma (PPARgamma) is strongly expressed in the intestinal epithelium, the role of PPARgamma in intestinal tumorigenesis has not yet been elucidated. To address this issue, we investigated the effect of PPARgamma inhibition and its mechanism on intestinal tumorigenesis using a selective antagonist, T0070907. We treated Apc(Min/+) mice and carcinogen-induced colon cancer model C57BL/6 mice with T0070907 and counted the number of spontaneous polyps and aberrant crypt foci and observed cell proliferation and beta-catenin protein in the colon epithelium. To investigate its mechanism, the changes of beta-catenin/TCF (T cell factor) transcriptional activity and location of beta-catenin induced by T0070907 were investigated in the colon cancer cell lines. T0070907 promoted polyp formation in the small intestine of Apc(Min/+) mice and aberrant crypt foci in the colon of C57BL/6 mice. PPARgamma inhibition promoted cell proliferation and increased expressions of the c-myc and cyclin D1 genes and the beta-catenin protein in the colon epithelium. In vitro, cell proliferation was promoted, but it was inhibited by the transfection of dominant-negative Tcf4. T0070907 increased beta-catenin/TCF transcriptional activity and beta-catenin protein in the cytsol and nucleus, but relatively decreased it on the cell membrane. PPARgamma antagonist promotes tumorigenesis in the small intestine and colon through stimulation of epithelial cell proliferation. beta-Catenin contributes to the promotion of tumorigenesis by PPARgamma antagonist due to activation of TCF/LEF (lymphoid enhancer factor) transcriptional factor.

Topics: Animals; Benzamides; beta Catenin; Cell Line, Tumor; Cell Proliferation; Colon; Colonic Neoplasms; Colonic Polyps; Cyclin D1; Epithelium; Gene Expression Regulation; Humans; Male; Mice; Mice, Inbred C57BL; PPAR gamma; Precancerous Conditions; Proto-Oncogene Proteins c-myc; Pyridines; TCF Transcription Factors

To investigate the expression of peroxisome proliferator-activated receptor-gamma (PPARgamma) in colon cancer cell lines and the effects of PPARgamma activation by its ligand troglitazone on cell growth in SW-480 cells.. PPARgamma expression was detected in Lovo, HT-29 and SW-480 cells using western blot. The effects of PPARgamma activation by its ligand troglitazone (TGZ) and selective antagonist T0070907 on cell growth were assessed by MTT and cell count methods; apoptosis was detected by flow cytometry method.. Western blot result revealed that PPARgamma protein was highly expressed in Lovo and HT-29 cells and there was relatively lower expression in SW-480 cells. Cell count method and MTT revealed that activation of SW-480 cells with TGZ resulted in inhibition of growth in a dose dependent manner. The effect of anti-proliferation increased with increasing doses of TGZ. Rates of growth inhibition were 3.3%, 8.3%, 25%, and 29% for different doses 5, 10, 20 and 25 micromol/L respectively. Flow cytometry method detected apoptosis in a dose-dependent manner. When the concentration of TGZ was less than 15 micromol/L , the apoptotic effect was found to be weak. The apoptotic effect was prominent when the concentration exceeded 20 micromol/L. Cell count method revealed that selective antagonist of PPARgamma stimulated cell growth of SW-480 cells in a dose dependent manner.. PPARgamma is expressed in colon cancer cells. Activation of PPARgamma by its ligands in colon cells has potent anti-proliferative and pro-apoptotic effects, suggesting that PPARgamma activation by its ligands may provide therapeutic value for colorectal cancer patients.

Topics: Antineoplastic Agents; Apoptosis; Benzamides; Blotting, Western; Cell Line, Tumor; Cell Proliferation; Cell Survival; Chromans; Colonic Neoplasms; Dose-Response Relationship, Drug; Flow Cytometry; HT29 Cells; Humans; Ligands; PPAR gamma; Pyridines; Thiazolidinediones; Troglitazone