Epigenetic inactivation of endothelin-2 and endothelin-3 in colon cancer
ABSTRACT Endothelin-1 (ET-1) and its receptors are overexpressed in human cancers, but much less is known about the roles of ET-2 and ET-3 in cancer etiology. We sought to examine human and rat colon tumors for dysregulation of ET-2 and ET-3 expression and determine the underlying mechanisms. Human primary colon cancers and carcinogen-induced rat colon tumors were subjected to real-time RT-PCR, immunoblotting and immunohistochemistry; EDN2 and EDN3 genes were examined by methylation-specific PCR, bisulfite sequencing and pyrosequencing; and forced expression of ET-2 and ET-3 was conducted in human colon cancer cells followed by real-time cell migration and invasion assays. Rat and human colon tumors had markedly reduced expression of ET-2 and ET-3 mRNA and protein compared with matched controls. Mechanistic studies revealed hypermethylation of EDN2 and EDN3 genes in human primary colon cancers and in a panel of human colon cancer cell lines. Forced expression of ET-2 and ET-3 attenuated significantly the migration and invasion of human colon cancer cells. We conclude that epigenetic inactivation of ET-2 and ET-3 occurs frequently in both rat and human colon cancers. Current therapeutic strategies target overexpressed members of the ET axis via small molecule inhibitors and receptor antagonists, but this work supports a complementary approach based on the re-expression of ET-2 and ET-3 as natural antagonists of ET-1 in colon cancer.
SourceAvailable from: Roderick Dashwood[Show abstract] [Hide abstract]
ABSTRACT: Histone deacetylase (HDAC) inhibitors are undergoing clinical trials as anticancer agents, but some exhibit resistance mechanisms linked to anti-apoptotic Bcl-2 functions, such as BH3-only protein silencing. HDAC inhibitors that reactivate BH3-only family members might offer an improved therapeutic approach. We show here that a novel seleno-α-keto acid triggers global histone acetylation in human colon cancer cells and activates apoptosis in a p21-independent manner. Profiling of multiple survival factors identified a critical role for the BH3-only member Bcl-2-modifying factor (Bmf). On the corresponding BMF gene promoter, loss of HDAC8 was associated with signal transducer and activator of transcription 3 (STAT3)/specificity protein 3 (Sp3) transcription factor exchange and recruitment of p300. Treatment with a p300 inhibitor or transient overexpression of exogenous HDAC8 interfered with BMF induction, whereas RNAi-mediated silencing of STAT3 activated the target gene. This is the first report to identify a direct target gene of HDAC8 repression, namely, BMF. Interestingly, the repressive role of HDAC8 could be uncoupled from HDAC1 to trigger Bmf-mediated apoptosis. These findings have implications for the development of HDAC8-selective inhibitors as therapeutic agents, beyond the reported involvement of HDAC8 in childhood malignancy.Cell Death & Disease 10/2014; 5:e1476. DOI:10.1038/cddis.2014.422 · 5.18 Impact Factor
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ABSTRACT: Pancreatic ductal adenocarcinoma (PDAC) has an extremely poor prognosis. Recently, it was reported that the endothelin B receptor (ETBR) of tumor endothelial cells prevents antitumor immunity. However, the immuno-histochemistry (IHC) conditions required to detect ETBR expression remain unclear. The aim of the present study was to confirm the appropriate conditions for IHC for ETBR using ETBR cDNA and transfectant cells and to assess ETBR expression in PDAC patients. An ETBR-expressing cell was established as an objective positive control and the detectability of ETBR expression was evaluated using several types of anti-ETBR antibodies. ETBR mRNA expression was then studied. Finally, ETBR expression was examined in human PDAC tissue using IHC. As a result, four different anti-ETBR antibodies recognized the cell surface ETBR appropriately. A non-specific reaction was shown in the detection of ETBR in normal human tissues. ETBR mRNA expression was weakly detected only in the adrenal gland. No biologically significant correlation was observed in the ETBR-IHC of human PDAC sections. In conclusion, it is necessary to perform IHC using an appropriate control to assess the tissue expression of ETBR.Oncology Reports 02/2014; 31(4). DOI:10.3892/or.2014.3031 · 2.19 Impact Factor
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ABSTRACT: Since the discovery of endothelin-1 in 1988, the main components of the signalling pathway have become established comprising three structurally similar endogenous twenty-one amino acids peptides, ET-1, ET-2 and ET-3, that activate two G-protein coupled receptors, ETA and ETB. . Our aim in this review is to highlight the recent progress in endothelin research. The endothelin-like domain peptide, corresponding to prepro-ET-193-166 , has been proposed to be co-synthesised and released with ET-1, to modulate the actions of the peptide. ET-1 remains the most potent vasoconstrictor in the human cardiovascular system with a particularly long lasting action. To date, the major therapeutic strategy to block the unwanted actions of ET in disease, principally in pulmonary arterial hypertension, has been to use antagonists that are selective for the ETA receptor (ambrisentan) or that block both receptor subtypes (bosentan). Macitentan represents the next generation of antagonists, being more potent than bosentan, with longer receptor occupancy and it is converted to an active metabolite; properties contributing to greater pharmacodynamic and pharmacokinetic efficacy. A second strategy is now being more widely tested in clinical trials and uses combined inhibitors of endothelin converting enzyme and neutral endopeptidase such as SLV306 (daglutril). A third strategy based on activating the ETB receptor, has led to the renaissance of the modified peptide agonist IRL1620 as a clinical candidate in delivering anti-tumour drugs and as a pharmacological tool to investigate experimental pathophysiological conditions. Finally we discuss biased signalling, epigenetic regulation and targeting with monoclonal antibodies as prospective new areas for endothelin research.British Journal of Pharmacology 08/2014; DOI:10.1111/bph.12874 · 5.07 Impact Factor