Boosting Wnt activity during colorectal cancer progression through selective hypermethylation of Wnt signaling antagonists

Abstract

BackgroundThere is emerging evidence that Wnt pathway activity may increase during the progression from colorectal adenoma to carcinoma and that this increase is potentially an important step towards the invasive stage. Here, we investigated whether epigenetic silencing of Wnt antagonists is the biological driver for this increased Wnt activity in human tissues and how these methylation changes correlate with MSI (Microsatelite Instability) and CIMP (CpG Island Methylator Phenotype) statuses as well as known mutations in genes driving colorectal neoplasia.MethodsWe conducted a systematic analysis by pyrosequencing, to determine the promoter methylation of CpG islands associated with 17 Wnt signaling component genes. Methylation levels were correlated with MSI and CIMP statuses and known mutations within the APC, BRAF and KRAS genes in 264 matched samples representing the progression from normal to pre-invasive adenoma to colorectal carcinoma.ResultsWe discovered widespread hypermethylation of the Wnt antagonists SFRP1, SFRP2, SFRP5, DKK2, WIF1 and SOX17 in the transition from normal to adenoma with only the Wnt antagonists SFRP1, SFRP2, DKK2 and WIF1 showing further significant increase in methylation from adenoma to carcinoma. We show this to be accompanied by loss of expression of these Wnt antagonists, and by an increase in nuclear Wnt pathway activity. Mixed effects models revealed that mutations in APC, BRAF and KRAS occur at the transition from normal to adenoma stages whilst the hypermethylation of the Wnt antagonists continued to accumulate during the transitions from adenoma to carcinoma stages.ConclusionOur study provides strong evidence for a correlation between progressive hypermethylation and silencing of several Wnt antagonists with stepping-up in Wnt pathway activity beyond the APC loss associated tumour-initiating Wnt signalling levels.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-891) contains supplementary material, which is available to authorized users.

MiR-339 and especially miR-766 reactivate the expression of tumor suppressor genes in colorectal cancer cell lines through DNA methyltransferase 3B gene inhibition

“…These tumor suppressor genes were shown to be regulated by methylation in the previous studies. 29,36 However, the level of promoter methylation of these genes in colon cancer cell lines in SW480 and HCT116 was significantly higher than that of HUVEC. Surprisingly, DNMT3B only decreased promoter methylation of SFRP1, SFRP2, DKK2 and WIF1 genes and did not alter the methylation levels of CDK2N2A, CACN2A and hMLH1.…”

“…For example, while some of these tumor suppressor genes can be methylated by DNMT-1, others are target of DNMT3. 36 Regulation of these well-known tumor suppressor genes (hMLH1, CDK2N2A and CACN2A) by other methyl transferases should be validated in future studies. Among tumor suppressor genes, it was shown that WIF1 was the most sensitive one to the effect of DNMT3B since in HCT-339, with no observed downregulation of DNMT3B, the methylation level of WIF1 was downregulated.…”

A DNS-metiláció szerepe és megváltozása az öregedés és a daganatos betegségek kialakulása során

“…Régóta ismert, hogy bizonyos, vastagbéldaganatokban azonosított hipermetilált gének, például egyes tumorszuppresszor gének inaktivációja fokozza a sejt proliferációt, így szelektív előnyt jelenthet a tumorsejtek számára [69,70]. Az 1. táblázat a vastagbéldaganatok-ban legfontosabb hipermetilált tumorszuppresszor markereket foglalja össze [71][72][73][74][75][76][77][78][79][80][81][82][83][84].…”

Epigenetic mechanisms in cancer: push and pull between kneaded erasers and fate writers

“…25 CpG methylation of Wnt antagonists such as SFRP5, SFRP1, SFRP2, Dickkopf Wnt signaling pathway inhibitor 2, Wnt inhibitory factor 1, wingless-type MMTV integration site family, member 3A, and SRY (sex determining region Y-box 17) were shown to significantly increase in the transition from normal tissues to adenoma. 27 Moreover, Wnt inhibitory factor 1, SFRP1, SFRP2, and Dickkopf Wnt signaling pathway inhibitor 2 were hypermethylated during transition from adenoma to carcinoma. Therefore, stepwise selective hypermethylation of several Wnt antagonists increases the expression of Wnt target genes during development of colon carcinoma.…”

“…Therefore, stepwise selective hypermethylation of several Wnt antagonists increases the expression of Wnt target genes during development of colon carcinoma. 27 Wnt signaling may be modulated by Wnt antagonists that interact with Wnt ligands themselves. For example, expression of SFRP5 and SFRP1 was markedly reduced in HBx-infected cells.…”