Epigenetic silencing in cancer cells is mediated by at least two distinct histone modifications, polycomb-based histone H3 lysine 27 trimethylation (H3K27triM) and H3K9 dimethylation. The relationship between DNA hypermethylation and these histone modifications is not completely understood. Using chromatin immunoprecipitation microarrays (ChIP-chip) in prostate cancer cells compared to normal prostate, we found that up to 5% of promoters (16% CpG islands and 84% non-CpG islands) were enriched with H3K27triM. These genes were silenced specifically in prostate cancer, and those CpG islands affected showed low levels of DNA methylation. Downregulation of the EZH2 histone methyltransferase restored expression of the H3K27triM target genes alone or in synergy with histone deacetylase inhibition, without affecting promoter DNA methylation, and with no effect on the expression of genes silenced by DNA hypermethylation. These data establish EZH2-mediated H3K27triM as a mechanism of tumor-suppressor gene silencing in cancer that is potentially independent of promoter DNA methylation.

Objectives Pancreatic stellate cells are source of dense fibrotic stroma, a constant pathological feature of chronic pancreatitis (CP) and pancreatic adenocarcinoma (PDAC). We observed correlation between levels of cyclooxygenase-2 (COX-2) and its product prostaglandin E2 (PGE2) and the extent of pancreatic fibrosis. Aim of this study was to delineate the effects of PGE2 on immortalized human pancreatic stellate cells (HPSC) and to identify the receptor involved. Methods IHC, RT-PCR and Q-RT-PCR were used to assess COX-2, extracellular matrix (ECM) and matrix metalloproteinases (MMP) gene expression. Eicosanoid profile was determined by LC/MS/MS. HPSC proliferation was assessed by MTS assay; migration by Boyden chamber assay and invasion using an invasion chamber. Transient silencing was obtained by siRNA. Results HPSC express COX-2 and synthesize PGE2. PGE2 stimulated HPSC proliferation, migration and invasion; stimulated expression of both ECM and MMP genes. HPSC expressed all four EP receptors. Only blocking the EP4 receptor resulted in abrogation of PGE2 mediated HPSC activation. Specificity of EP4 for the effects of PGE2 on stellate cells was confirmed using specific antagonists. Conclusion Our data indicate that PGE2 regulates PSC profibrotic activities via EP4 receptor thus suggesting EP4 receptor as useful therapeutic target for pancreatic cancer to reduce desmoplasia.

Objectives-Pancreatic stellate cells are source of dense fibrotic stroma, a constant pathological feature of chronic pancreatitis (CP) and pancreatic adenocarcinoma (PDAC). We observed correlation between levels of cyclooxygenase-2 (COX-2) and its product prostaglandin E2 (PGE 2 ) and the extent of pancreatic fibrosis. Aim of this study was to delineate the effects of PGE 2 on immortalized human pancreatic stellate cells (HPSC) and to identify the receptor involved. The authors have no any potential conflict of interest including any financial, personal, or other relationships with other people or organizations that could inappropriately influence this work. MethodsPublisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptPancreas. Author manuscript; available in PMC 2014 April 01. by LC/MS/MS. HPSC proliferation was assessed by MTS assay; migration by Boyden chamber assay and invasion using an invasion chamber. Transient silencing was obtained by siRNA.Results-HPSC express COX-2 and synthesize PGE 2 . PGE 2 stimulated HPSC proliferation, migration and invasion; stimulated expression of both ECM and MMP genes. HPSC expressed all four EP receptors. Only blocking the EP4 receptor resulted in abrogation of PGE 2 mediated HPSC activation. Specificity of EP4 for the effects of PGE 2 on stellate cells was confirmed using specific antagonists.Conclusion-Our data indicate that PGE 2 regulates PSC profibrotic activities via EP4 receptor thus suggesting EP4 receptor as useful therapeutic target for pancreatic cancer to reduce desmoplasia.