Oesophageal squamous cell carcinoma may develop within a background of accumulating DNA methylation in normal and dysplastic mucosa

Abstract

Background: Oesophageal squamous cell carcinoma (OSCC) often arises from preceding dysplastic lesions in the oesophageal epithelium. However, the molecular changes occurring in premalignant lesions are not well understood. An epigenetic change is an example of OSCC that may occur within the epithelium. Aim: To investigate the methylation status of multiple promoters in cancer-derived DNA, as well as in the background epithelium of OSCC, including dysplastic lesions and non-neoplastic mucosa. The normal epithelium from patients without cancer was also examined. The findings were correlated with the mutational status of p53. Patients and methods: 56 patients with advanced OSCC, 21 patients with intraepithelial neoplasia (IEN), 56 patients with a background of non-neoplastic epithelium, adjacent to the OSCC, and 42 normal control epithelia from healthy volunteers were studied. The promoter methylation status of SFRP1, SFRP2, DCC, APC, p16 INK4a , p14 ARF , MINT1, MINT2, MINT31, CACNA1G, COX2, DAPK, hMLH1 and MGMT was examined by methylation-specific single polymerase chain reaction or combined bisulphite restriction analysis. The mutation of p53 by direct sequencing was assessed. Results: DNA methylation was observed in OSCC and in its background epithelium. The frequency of CpG island methylation increased from a baseline level in the background non-neoplastic epithelium, through IEN, to advanced OSCC. However, mutations in p53 were almost exclusively observed in IEN and OSCC. More extensive DNA methylation was seen in the neoplastic lesions (OSCC or IEN) having a p53 mutation than in those with wild-type p53. Conclusion: DNA methylation is present at low levels in the non-neoplastic oesophageal epithelium and appears to contribute to the progression of the dysplasia-carcinoma sequence in OSCC carcinogenesis. D espite the increased incidence of oesophageal adenocarcinoma in the Western World, oesophageal squamous cell carcinoma (OSCC) remains a common type of malignancy worldwide. Tumorigenesis of OSCC is a multistep process and OSCC often develops multifocally within the oesophageal epithelium. Environmental and dietary factors, such as alcohol, tobacco, and high levels of nitrates in the soil and drinking water, have been associated with the aetiology of OSCC. Mutations in the p53 gene are one of the most frequent genetic changes observed in oesophageal cancer and dysplasia.3-5 A varying p53 mutational status is often observed in multiple lesions from the same patient with OSCC.6 Wide areas within the oesophageal mucosa become simultaneously genetically unstable after a prolonged exposure to carcinogens, leading to a pattern of neoplastic transformation described as ''field carcinogenesis''. [7][8][9] Epigenetic changes in DNA without concomitant changes in the underlying genetic code are now known to occur often in human cancers. [10][11][12] Promoter hypermethylation and resulting transcriptional repression of functionally important cancerrelated tumour suppressor genes appear to drive tumorigenesis. The prom...

Revisit of Field Cancerization in Squamous Cell Carcinoma of Upper Aerodigestive Tract: Better Risk Assessment with Epigenetic Markers

“…Mutations of p53 or p53 oncoprotein are relatively late events in carcinogenesis (42,43), so, despite their biological plausibility as cancer predictors, they are insufficient for risk assessments for SCC in the UADT. Because aberrant DNA methylation usually precedes neoplastic transformation, qualitative studies have suggested that the presence of methylated genes may increase in a sequence from normal mucosa to precursor lesions to SCC (44)(45)(46). Our study further found that this phenomenon is quantitative for individual gene markers.…”

Hypermethylation of theAKAP12Promoter is a Biomarker of Barrett's-Associated Esophageal Neoplastic Progression

“…Based on a panel of 14 promoter loci, it has recently been reported that nonneoplastic epithelium from patients with ESCC is significantly more methylated than control esophageal epithelium from healthy volunteers, and that this may contribute to progression in the dysplasia-carcinoma sequence in ESCC (30). Similarly, in the current study, AKAP12 hypermethylation was significantly higher in NEcA than in NE or NEcS, whereas no such trend was observed for NEcS versus NE.…”

“…Previous studies have shown the importance of hypermethylation of gene promoters in histologically normal tissue as this event relates to the initiation of carcinoma (25)(26)(27)(28)(29)(30). By methylation-specific in situ PCR and in situ RNA and protein analysis, methylation of the MLH1 promoter was observed in small foci of normal colonic epithelial cells from patients with colon cancer and associated silencing of this gene, but not in sections of normal colon from healthy volunteers, suggesting that tumors with gene silencing due to epigenetic alteration may evolve from rare clones of methylated cells in normal epithelium (29).…”

Hypermethylation of multiple tumor-related genes associated with DMNT3b up-regulation served as a biomarker for early diagnosis of esophageal squamous cell carcinoma

“…The proportions of positive cells were evaluated using the scoring system to determine as negative (-) to extremely strong positive (++++) staining. 30 Kuroki et al also showed high methylation frequency for RAR-β in non-tumor esophageal samples, 23 and a recent study indicated that smoking-damaged esophageal epithelium, even histologically normal, had suffered epigenetic changes. 27 Thus, our data suggest that the methylated alleles in the paired non-tumor tissues may represent premalignant changes and p16, CDH1, DAPK and RAR-β may be of the possible targets for predicting cancer risk and/or making an early cancer diagnosis.…”