Antitumor Effects Of Troglitazone And The Related Mechanism

BACKGROUND & OBJECTIVE:Prostate cancer(PC) is the most common malignancy diagnosed in men and the mortality rate of prostate cancer continues unabated. Peroxisome proliferator-activated receptors (PPARs) are a family of ligand-activated transcription factors belonging to the nuclear receptor superfamily. Troglitazone, a thiazolidinedione ligand of PPARγ, has been recently described as possessing antitumoral properties, but the mechanism remains unclear. This study aimed to explore the antitumor effects and the related mechanism of troglitazone in vitro and in vivo with prostate cancer cell line PC-3 as target cell.METHODS:in vitro experiment:MTT, flow cytometry, Western blot, RT-PCR, immunohistochemistry, transwell chamber were performed to analyze the proliferation, apoptosis and invasion of the prostate cells after treatment of troglitazone. in vivo experiment:Establish the murine exnograft model, the growth of tumor was messured in vivo. Flow cytometry, RT-PCR and Western blot were performed to analyze caspase activity, Bcl-2 mRNA and protein expression.RESULTS:in vitro experiment:MTT assay demonstrated that troglitazone, in a dose- and time- dependent manner, inhibited the growth of PC-3 cells independent of PPARγ. In addition, TGZ induced cell cycle arrest and apoptosis. Cell scratch and transwell chamber assay showed that the ability of migration and invasion of PC-3 cells decreased significantly in the presence of troglitazone. Along with the increase of troglitazone concentration, Bcl-2 mRNA and protein expression decreased, Bax mRNA and protein expression had no change and the ratio of Bcl-2 to Bax significantly decreased. Flow cytometry showed that Dym Depolarization in PC-3 cells decreased and the positive rates of activated Caspase-3 increased when treated with troglitazone. Moreover, inhibitor of caspase-activated DNAse (ICAD), the substrate of Caspase-3, was degraded. Further study of the intracellular mechanism showed that EGFR, ERK1/2, PI3K and AKT expression decreased along with the increase of troglitazone concentration, whereas the proliferation and apoptosis rate had no obvious change in the EGFR inhibition group. In vivo experiment: The growth of tumor was visibly suppressed in vivo. Apoptosis results indicated that the apoptosis rate and the positive rates of activated Caspase-3 increased in troglitazone groups and the ratio of Bcl-2 to Bax decreased.CONCLUSION:Troglitazone can suppress growth, induce apoptosis and inhibit invasion of PC-3 cells, possibly by decreasing the expression of EGFR, ERK1/2, PI3K, AKT, the ratio of Bcl-2 to Bax, Dym Depolarization and increasing the positive rates of activated Caspase-3 through PPARy independent mechanism.