Peroxisome Proliferator-Activated Receptor-γ Activator 15-Deoxy-Δ 12,14-Prostaglandin J 2 Inhibits Neuroblastoma Cell Growth through Induction of Apoptosis: Association with Extracellular Signal-Regulated Kinase Signal Pathway

Abstract

Peroxisome proliferator-activated receptor-γ (PPAR-γ) ligands have been demonstrated to inhibit growth of several cancer cells. Here, we investigated whether one of the PPAR-γ ligands, 15-deoxy-Δ 12,14-prostaglandin J2 (15-deoxy-PGJ 2) inhibits cell growth of two human neuroblastoma cells (SK-N-SH and SK-N-MC) in a PPAR-γ-dependent manner. PPAR-γ was expressed in these cells, and 15-deoxy-PGJ 2 increased expression, DNA binding activity, and transcriptional activity of PPAR-γ. 15-Deoxy-PGJ 2 also inhibited cell growth in time- and dose-dependent manners in both cells. Cells were arrested in G 2/M phase after 15-deoxy-PGJ 2 treatment with concomitant increase in the expression of G 2/M phase regulatory protein cyclin B1 but decrease in the expression of cdk2, cdk4, cyclin A, cyclin D1, cyclin E, and cdc25C. Conversely, related to the growth inhibitory effect, 15-deoxy-PGJ 2 increased the induction of apoptosis in a dose-dependent manner. Consistent with the induction of apoptosis, 15-deoxy-PGJ 2 increased the expression of proapoptotic proteins caspase 3, caspase 9, and Bax but down-regulated antiapoptotic protein Bcl-2. 15-Deoxy-PGJ 2 also activated extracellular signal-regulated kinase (ERK) 2. In addition, mitogen-activated protein kinase kinase (MEK) 1/2 inhibitor PD98059 (2′-amino-3′-methoxyflavone) decreased 15-deoxy-PGJ 2-induced ERK2 activation, and expression of PPAR-γ, capase-3, and cyclin B1. Moreover, MEK1/2 inhibitor PD98059 significantly prevented against the 15-deoxy-PGJ 2-induced cell growth inhibition. We also found that PPAR-γ antagonist GW9662 (2-chloro-5-nitro-N-phenylbenzamide) reversed the 15-deoxy-PGJ 2-induced cell growth inhibition, PPAR-γ expression, and activation of ERK2. These results demonstrate that 15-deoxy-PGJ 2 inhibits growth of human neuroblastoma cells via the induction of apoptosis in a PPAR-γ-dependent manner through activation of ERK pathway and suggest that 15-deoxy-PGJ 2 may have promising application as a therapeutic agent for neuroblastoma.