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 ET3 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.

Endothelin-2 Differential Expression in Normal and Early-Stages of Colon Cancer Development

“…The immunofluorescence pattern is coincident with these results, since most of the crypts are negatives for that peptide and only a weak reaction can be seen. Coincident with our results, recent studies on colon cancer induction models, have reported an epigenetic silencing of the ET-2 gene several weeks before the onset of frank tumors [11]. As was previously mentioned, distal colon exhibit the major tumors rate in early stages of cancer induction [12], theref re ET-2 down regulation o may be an early prognostic marker of the disease.…”

“…While in premalignant adenomas and malignant colon carcinomas, exhibit increased levels of preproET-1, endothelin-converting enzymes, and ET-1 [7,8], there is no consensus about how the ETA and ETB receptors behave [9,10]. 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 [11]. 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.…”

Aspects of the endothelin system in colorectal cancer

“…Thus, in human and rat colon cancer cell lines as well as in human primary colon cancers, there is down-regulation and hyper-methylation of the EDN-2 and EDN-3 genes. For their structural similarity, EDN-2 and EDN-3 can be considered as natural competitors for the EDN-1 receptor and as natural antagonists of EDN-1, and in line with this notion they have anticancer effects (3). A short summary is shown in Table 1 regarding the increased expression of members of the EDN system in colon cancer cell lines SW480, SW620 and HT29 following exposure to the demethylating agent 5-aza-2′-deoxycytidine (unpublished own results).…”

“…The EDN system consists of endothelin-1 (EDN-1), endothelin-2 (EDN-2), endo thelin-3 (EDN-3), the G-protein-coupled receptors, endothelin receptor type A (EDNRA) and endothelin receptor type B (EDNRB), and endothelin converting enzyme (ECE) (3). Endothelins are characterized by a single alpha-helix and two disulfide bridges.…”

New Therapeutic Schedule for Prostatic Cancer-3 Cells with ET-1 RNAi and Endostar

“…The endothelin axis is found to be an important role in tumorigenesis and progression in many types of human cancers (Rotondo et al, 2012;Shao et al, 2013;Tamkus et al, 2013;Wang et al, 2013a). ET-1, as an important role in endothelin system, has the potential to be examination indicator (Kalles et al, 2012) and therapy target (Ling et al, 2013;Rosano et al, 2013) for cancers.…”