15-Deoxy-Δ12,14-prostaglandin J2 Upregulates the Expression of 15-Hydroxyprostaglandin Dehydrogenase by Inducing AP-1 Activation and Heme Oxygenase-1 Expression in Human Colon Cancer Cells.

Abstract

BackgroundAbnormal upregulation of prostaglandin E2 (PGE2) is considered to be a key oncogenic event in the development and progression of inflammation-associated human colon cancer. It has been reported that 15-hydroxyprostaglandin dehydrogenase (15-PGDH), an enzyme catabolizing PGE2, is ubiquitously downregulated in human colon cancer. 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), a peroxisome proliferator-activated receptor γ ligand, has been shown to have anticarcinogenic activities. In this study, we investigate the effect of 15d-PGJ2 on expression of 15-PGDH in human colon cancer HCT116 cells.MethodsHCT116 cells were treated with 15d-PGJ2 analysis. The expression of 15-PGDH in the treated cells was measured by Western blot analysis and RT-PCR. In addition, the cells were subjected to a 15-PGDH activity assay. To determine which transcription factor(s) and signaling pathway(s) are involved in 15d-PGJ2-induced 15-PGDH expression, we performed a cDNA microarray analysis of 15d-PGJ2-treated cells. The DNA binding activity of AP-1 was measured by an electrophoretic mobility shift assay. To determine whether the AP-1 plays an important role in the 15d-PGJ2-induced 15-PGDH expression, the cells were transfected with siRNA of c-Jun, a major subunit of AP-1. To elucidate the upstream signaling pathways involved in AP-1 activation by 15d-PGJ2, we examined its effect on phosphorylation of Akt by Western blot analysis in the presence or absence of kinase inhibitor.Results15d-PGJ2 (10 μM) significantly upregulated 15-PGDH expression at the mRNA and protein levels in HCT-116 cells. 15-PGDH activity was also elevated by 15d-PGJ2. We observed that genes encoding C/EBP delta, FOS-like antigen 1, c-Jun, and heme oxygenase-1 (HO-1) were most highly induced in the HCT116 cells following 15d-PGJ2 treatment. 15d-PGJ2 increased the DNA binding activity of AP-1. Moreover, transfection with specific siRNA against c-Jun significantly reduced 15-PGDH expression induced by 15d-PGJ2. 15d-PGJ2 activates Akt and a pharmacological inhibitor of Akt, LY294002, abrogated 15d-PGJ2-induced 15-PGDH expression. We also observed that an inhibitor of HO-1, zinc protoporphyrin IX, also abrogated upregulation of 15-PGDH and down-regulation of cyclooxygenase-2 expression induced by 15d-PGJ2.ConclusionsThese finding suggest that 15d-PGJ2 upregulates the expression of 15-PGDH through AP-1 activation in colon cancer HCT116 cells.