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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 (lEN), 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 SFRPI, SFRP2, DCC, APC, p16 INK4a,4ARF MINT1, MINT2, MINT31, CACNA1G, COX2, DAPK, hMLH1 and MGMTwas 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 lEN, to advanced OSCC. However, mutations in p53 were almost exclusively observed in lEN and OSCC. More extensive DNA methylation was seen in the neoplastic lesions (OSCC or lEN) 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. [ABSTRACT FROM AUTHOR]