Long-range epigenetic silencing at 2q14.2 affects most human colorectal cancers and may have application as a non-invasive biomarker of disease

Large chromosomal regions can be suppressed in cancer cells as denoted by hypermethylation of neighbouring CpG islands and downregulation of most genes within the region. We have analysed the extent and prevalence of long-range epigenetic silencing at 2q14.2 (the first and best characterised example of coordinated epigenetic remodelling) and investigated its possible applicability as a non-invasive diagnostic marker of human colorectal cancer using different approaches and biological samples. Hypermethylation of at least one of the CpG islands analysed (EN1, SCTR, INHBB) occurred in most carcinomas (90%), with EN1 methylated in 73 and 40% of carcinomas and adenomas, respectively. Gene suppression was a common phenomenon in all the tumours analysed and affected both methylated and unmethylated genes. Detection of methylated EN1 using bisulfite treatment and melting curve (MC) analysis from stool DNA in patients and controls resulted in a predictive capacity of, 44% sensitivity in positive patients (27% of overall sensitivity) and 97% specificity. We conclude that epigenetic suppression along 2q14.2 is common to most colorectal cancers and the presence of a methylated EN1 CpG island in stool DNA might be used as biomarker of neoplastic disease

Engrailed-1 Negatively Regulates β-Catenin Transcriptional Activity by Destabilizing β-Catenin via a Glycogen Synthase Kinase-3β–independent Pathway

The Wnt signaling pathway plays a major role in development, and upon deregulation it is implicated in neoplasia. The hallmark of the canonical Wnt signal is the protection of β-catenin from ubiquitination and proteasomal degradation induced by glycogen synthase kinase (GSK)-3β inhibition. The stabilized β-catenin translocates to the nucleus where it binds to T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription factors, activating the expression of Wnt target genes. In the absence of Wnt signal, TCF/LEF bind to Groucho (Gro)/TLE corepressors and repress Wnt target genes. Gro/TLE bind also to Engrailed (En) transcription factors mediating En-repressive activity on En target genes. Here, we present data suggesting that En-1 serves also as a negative regulator of β-catenin transcriptional activity; however, its repressive effect is independent of Gro/TLE. Our data suggest that En-1 acts by destabilizing β-catenin via a proteasomal degradation pathway that is GSK-3β–independent. Moreover, because En-1-mediated β-catenin degradation is also Siah independent, our data imply that En-1 exerts its repressive effect by a novel mechanism negatively controlling the level of β-catenin