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: Mariana Bianchi
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- "While in premalignant adenomas and malignant colon carcinomas, exhibit increased levels of pre- proET-1, endothelin-converting enzymes, and ET-1  , there is no consensus about how the ETA and ETB receptors behave  . On the other hand, it has been recently proved that ET-2 and ET-3 are silenced in colon cancer and their induced overexpressions inhibit cell migration and invasion . In that work, it was hypothesized that ET-2 and ET-3 might be silenced in early stages of cancer avoiding " mixed messages " in the ET axis. "
ABSTRACT: The endothelin family has been related with several pathological diseases including cardiovascular disorders, hyperten-sion and cancer. However, little is known about endothelin system in early stages of colorectal cancer and there are no studies evaluating differences in proximal and distal colon segments. To deepen in this issue, we have studied the en-dothelin's family gene and protein expression in normal mice and early stage of a mice model of Azoxymethane (AOM) and Dextran Sodium Sulphate (DSS) induced colorectal cancer in proximal and distal segments. Additionally, using nonlinear microscopy (NLM) techniques, we have characterized collagen changes in early stages of cancer disease de-velopment. In the present study, we have found significant differential gene expression and protein localization between these colon regions, which allow us to hypothesize a new role for the ET-2 as an early marker of colon cancer devel-opment.Journal of Cancer Therapy 06/2013; 4(06). DOI:10.4236/jct.2013.46A2004
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ABSTRACT: Background MicroRNAs (miRNAs or miRs) are short non-coding RNAs that affect the expression of genes involved in normal physiology, but that also become dysregulated in cancer development. In the latter context, studies to date have focused on high-abundance miRNAs and their targets. We hypothesized that among the pool of low-abundance miRNAs are some with the potential to impact crucial oncogenic signaling networks in colon cancer. Results Unbiased screening of over 650 miRNAs identified miR-206, a low-abundance miRNA, as the most significantly altered miRNA in carcinogen-induced rat colon tumors. Computational modeling highlighted the stem-cell marker Krüppel-like factor 4 (KLF4) as a potential target of miR-206. In a panel of primary human colon cancers, target validation at the mRNA and protein level confirmed a significant inverse relationship between miR-206 and KLF4, which was further supported by miR-206 knockdown and ectopic upregulation in human colon cancer cells. Forced expression of miR-206 resulted in significantly increased cell proliferation kinetics, as revealed by real-time monitoring using HCT116 cells. Conclusions Evolutionarily conserved high-abundance miRNAs are becoming established as key players in the etiology of human cancers. However, low-abundance miRNAs, such as miR-206, are often among the most significantly upregulated miRNAs relative to their expression in normal non-transformed tissues. Low-abundance miRNAs are worthy of further investigation, because their targets include KLF4 and other pluripotency and cancer stem-cell factors.09/2012; 4(1). DOI:10.1186/1868-7083-4-16
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ABSTRACT: Activation of autocrine and paracrine signalling by endothelin 1 (ET1) binding to its receptors elicits pleiotropic effects on tumour cells and on the host microenvironment. This activation modulates cell proliferation, apoptosis, migration, epithelial-to-mesenchymal transition, chemoresistance and neovascularization, thus providing a strong rationale for targeting ET1 receptors in cancer. In this Review, we discuss the advances in our understanding of the diverse biological roles of ET1 in cancer and describe the latest preclinical and clinical progress that has been made using small-molecule antagonists of ET1 receptors that inhibit ET1-driven signalling.Nature Reviews Cancer 07/2013; DOI:10.1038/nrc3546 · 29.54 Impact Factor