Rosiglitazone enhances fluorouracil-induced apoptosis of HT-29 cells by activating peroxisome proliferator-activated receptor γ

Abstract

To examine whether and how rosiglitazone enhances apoptosis induced by fluorouracil in human colon cancer (HT-29) cells. Human colon cancer HT-29 cells were cultured in vitro and treated with fluorouracil and/or rosiglitazone. Proliferation and growth of HT-29 cells were evaluated by MTT assay and trypan blue exclusion methods, respectively. The apoptosis of HT-29 cells was determined by acridine orange/ethidium bromide staining and flow cytometry using PI fluorescence staining. The expressions of peroxisome proliferator-activated receptor gamma (PPARgamma), Bcl-2 and Bax in HT-29 cells were analyzed by Western blot. Although rosiglitazone at the concentration below 30 micromol/L for 72 h exerted almost no inhibitory effect on proliferation and growth of HT-29 cells, it could significantly enhance fluorouracil-induced HT-29 cell proliferation and growth inhibition. Furthermore, 10 micromol/L rosilitazone did not induce apoptosis of HT-29 cells but dramatically enhanced fluorouracil-induced apoptosis of HT-29 cells. However, rosiglitazone did not improve apoptosis induced by fluorouracil in HT-29 cells pretreated with GW9662, a PPARgamma antagonist. Meanwhile, the expression of Bax and PPARgamma was up-regulated, while the expression of Bcl-2 was down regulated in HT-29 cells treated with rosiglitazone in a time-dependent manner. However, the effect of rosiglitazone on Bcl-2 and Bax was blocked or diminished in the presence of GW9662. Rosiglitazone enhances fluorouracil-induced apoptosis of HT-29 cells by activating PPARgamma.