Growth inhibition of esophageal squamous carcinoma cells by peroxisome proliferator-activated receptor-gamma ligands.

The growth of human cancer cells expressing peroxisome proliferator-activated receptor-gamma (PPAR-gamma) has been reported to be inhibited by PPAR-gamma ligands. In esophageal squamous-cell carcinoma cell lines T.T, T.Tn, and EC-GI-10, we detected expression of PPAR-gamma and investigated the effects of PPAR-gamma ligands on these cell lines in vitro with the use of troglitazone, pioglitazone, and 15d-PGJ2. Marked growth inhibition by the PPAR-gamma ligands was observed in all cases. The growth-inhibitory effect was evidenced by a dose-dependent inhibition of deoxyribonucleic acid synthesis and was associated with altered cell-cycle progression manifesting G1 arrest. Cell-cycle arrest in T.Tn cells induced by troglitazone could be correlated with an increased level of cyclin-dependent kinase inhibitor p27(Kip1), p21(Cip1/Waf1), and p18(Ink4c). Moreover, troglitazone treatment increased the expression of interleukin-1 alpha, a multifunctional cytokine implicated in antitumor immunity. These findings suggest that troglitazone and other PPAR-gamma ligands have adjuvant or neoadjuvant therapeutic potentials in esophageal cancer.