Abstract
Peroxisome proliferator‐activated receptor‐gamma (PPAR‐γ) is a member of the nuclear hormone receptor superfamily of ligand‐activated transcription factors and a crucial regulator of cellular differentiation. PPAR‐γ ligands have been demonstrated to inhibit growth of several cancer cells. In this study, two human lung cancer cells (NCI‐H23 and CRL‐2066) and one human lung normal cell (CRL‐202) were used for the experiments. The results showed that in consistence with the loss of viability, troglitazone (TGZ) induced apoptosis of CRL‐2066 and NCI‐H23 cells but not CCL‐202 cells. TGZ upregulated PPAR‐γ expression in all the three lung cell lines, especially in the cancer cells. In association of the time‐dependent inhibition of the cell proliferation, TGZ downregulated the expression of Bcl‐w and Bcl‐2 but activated extracellular signal‐regulated kinase (ERK)1/2 and p38, suggesting that the growth‐inhibitory effect of TGZ is associated with the reduction of Bcl‐w and Bcl‐2 and the increase of ERK1/2 and p38 activation. SAPK/JNK activation assay showed a decreased activity in all the three cell lines tested after TGZ treatment. It was also demonstrated that TGZ could activate PPAR‐γ transcriptionally. We conclude that TGZ inhibits growth of human lung cancer cells via the induction of apoptosis and the inhibition of cell growth, at least in part, in a PPAR‐γ‐relevant manner. The mechanism of TGZ is associated with the activation of ERK and p38, the reduction of SAPK/JNK activity, and the alteration of Bcl‐w and Bcl‐2. © 2005 Wiley‐Liss, Inc.