Activation of peroxisome proliferator-activated receptor gamma inhibits cell growth via apoptosis and arrest of the cell cycle in human colorectal cancer

作者：Lin Mao Song; chen We Chang^*; Bai Xia; Wang Ya Dong

来源：Journal of Digestive Diseases, 2007, 8(2): 82-88.

DOI：10.1111/j.1443-9573.2007.00290.x

• apoptosis
• cell cycle
• colorectal cancer
• PPAR gamma

OBJECTIVE: To investigate the expression of peroxisome proliferator-activated receptors (PPAR)gamma and the effects of PPAR gamma ligands on cells growth in colorectal cancer (CRC) cell line HT-29, and to explore whether the activation of PPARy by its selective ligand can induce apoptosis and the arrest of the cell cycle in these cells.
METHODS: A CRC cell line, HT-29, was used in this study. PPAR gamma mRNA and the protein expressions were measured by reverse transcriptase-polymerase chain reaction and Western blot. The HT-29 cells were treated with two specific PPAR gamma ligands: rosiglitazone and 15-d-PGJ(2). The effects of PPAR gamma activated by rosiglitazone and 15-d-PGJ(2) on the anchorage-dependent and anchorage-independent growth of the cells were assessed by methylthiazolyl terazolium (MTT) and soft agar colony assay, respectively. Apoptosis was measured by TUNEL staining and flow cytometry (FCM) assay by CaspSCREEN (TM) Flowcytometric Apoptosis Detection Kit (BioVision, Palo Alto, USA). Furthermore, the caspase-3 expression was determined by a immunocytochemical staining method before and after treatment with rosiglitazone and 15-d-PGJ(2), for 48 h. The cell cycles were measured by flow cytometric analysis using propidium iodide (PI).
RESULTS: PPAR gamma mRNA and protein expressions were observed in the HT-29 cells. The MTT assay showed that treatment of these cells with 0, 0.1, 1 or 10 mu mol/L PPAR gamma activators rosiglitazone or 15-d-PGJ(2) for 0, 24, 48 or 72 h resulted in the inhibition of anchorage-dependent cell growth in a dosage- and time-dependent way. Rosiglitazone treatment during cell growth resulted in the reduction of colony formation and the effects were not immediately reversible in the cell culture. TUNEL staining showed DNA fragmentation in positive cells after treatment with rosiglitazone and 15d-PGJ(2) for 48 h. In addition, FCM showed that the apoptosis rates were 14.8 +/- 0.8% and 28.5 +/- 1.3% or 15 +/- 0.7% and 40 +/- 1.2% after the cells were incubated with 10 mu mol/L rosiglitazone or 15-d-PGJ(2) for 24 h and 48 h, while the apoptosis rates of cells without treatment were 3.8 +/- 0.4% and 8.8 +/- 0.4%, respectively Consistent with these results, the positivity rates of caspase-3 expression in cells treated with rosiglitazone or 15-d-PGJ(2) increased significantly when compared with the control group. To explore whether the regulation of the cell cycle was involved in the effect of PPAR gamma ligands on cell growth, FCM using PI staining was assessed. The ratio of G(0)/G(1), phase cells increased after incubated with 10 mu mol/L rosiglitazone or 15-d-PGJ(2) for 24 h and 48 h.
CONCLUSIONS: Our results showed that PPAR gamma was expressed in HT-29 cells and PPAR gamma activation could inhibit cell growth through inducing apoptosis and suppressing the cell cycle. PPAR gamma may be considered as a new therapeutic target for colon cancer in humans.

• 出版日期2007-5
• 单位苏州大学