Search

15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme that catalyses the conversion of prostaglandin E2 to a keto metabolite. The expression of 15-PGDH is ubiquitously repressed in various human malignancies. However, the molecular mechanisms underlying down-regulation of 15-PGDH expression remain largely unknown. 15-Deoxy-△12,14-prostaglandin J2 (15d-PGJ2), an endogenous ligand of peroxisome proliferator-activated receptor γ, has been reported to have anti-inflammatory and anticarcinogenic activities. In the present study, we have found that 15d-PGJ2 induces expression and catalytic activity of 15-PGDH in human breast cancer (MDA-MB-231) cells. 15d-PGJ2 decreased the level of CpG methylation in the 15-PGDH promoter in MDA-MB-231 cells as determined by the bisulphite genome sequencing and methyl-specific PCR. 15d-PGJ2 inhibited the catalytic activity of methyltransferase 1 (DNMT1) but did not influence its expression. Biotinylated 15d-PGJ2 directly interacted with DNMT1 and reduced its catalytic activity. Chromatin-immunoprecipitation analysis revealed that 15d-PGJ2 significantly attenuated DNMT1 binding to the activator protein-1 transcription factor present in the 15-PGDH promoter region. A nonelectrophilic analogue 9,10-dihydro-15d-PGJ2 failed to suppress the methylation of CpG islands present in 15-PGDH promoter and did not affect both DNMT1 activity and 15-PGDH expression. These findings suggest that the α,β-unsaturated carbonyl group present in 15d-PGJ2 is essential for its inactivation on DNMT1 and expression of 15-PGDH. In conclusion, 15d-PGJ2 plays as a hypomethylating agent through direct interaction with DNMT1 and consequently suppresses DNMT1-mediated hypermethylation of 15-PGDH promoter, leading to up-regulation of 15-PGDH expression. [ABSTRACT FROM AUTHOR]

15-Deoxy-Δ12,14-prostaglandin J2(15d-PGJ2), a representative J-series cyclopentenone prostaglandin, has biphasic roles in cell proliferation and apoptosis. Hypoxia inducible factor-1 (HIF-1) regulates expression of various genes involved in tumor growth and angiogenesis. In the present study, treatment of human breast cancer (MCF-7) cells with 15d-PGJ2resulted in the accumulation of the α-subunit of HIF-1. Pretreatment with zinc protoporphyrin IX, a pharmacological inhibitor of heme oxygenase-1 (HO-1), as well as siRNA knockdown ofHO-1gene in MCF-7 cells attenuated 15d-PGJ2-mediated HIF-1α accumulation. 15d-PGJ2treatment increased intracellular production of reactive oxygen species (ROS), which was mediated by HO-1 induction. Preincubation of MCF-7 cells with trolox, a water-soluble form of vitamin E, attenuated 15d-PGJ2-induced HIF-1α expression although HO-1 expression was unchanged. This finding suggests that ROS accumulated as a consequence of HO-1 up-regulation can enhance HIF-1α expression in MCF-7 cells treated with 15d-PGJ2. Alternatively, 15d-PGJ2was found to covalently bind to HIF-1α prolyl-4-hydroxylase 2 (PHD2) in MCF-7 cells, which hampers the proline hydroxylation of HIF-1α, thereby disrupting ubiquitin-dependent proteasomal degradation of this transcription factor. Pretreatment with thiol reducing agents blunted 15d-PGJ2-induced HIF-1α stabilization, indicative of a cysteine residue as a direct target of 15d-PGJ2. Molecular docking analysis suggests that 15d-PGJ2preferentially binds to PHD2 in the vicinity of the Cys201residue based on binding energies and carbon–sulfur distances. In summary, 15d-PGJ2stabilizes HIF-1α in MCF-7 cells through HO-1 induction with subsequent ROS generation and also through direct modification of PHD2. [ABSTRACT FROM AUTHOR]