Identification of DNA methylation changes in esophageal cancer before/after chemoradiation therapy using a MCA-microarray and bisulfate pyrosequencing.

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10550 Background: Systemic chemo- and chemoradiation therapies for esophageal squamous cell carcinoma (ESCC) patients are widely accepted. However we sometimes experience the resistance of ESCC to these therapies, and multicentric occurrence of ESCC after the successful treatment. Although there are studies, which have shown the involvements of promoter methylation of tumor suppressor genes in esophageal carcinogenesis, it remains unclear that the epigenetic changes related to treatments against ESCC. Our aim is to identify how DNA methylation status changes in tumor tissue (T) and also adjacent normal tissue (ADJ) before/after chemoradiation therapy (CRT). Methods: Tumor and adjacent normal biopsy specimens were obtained before/after treatment from 34 patients (124 samples) treated with a uniform CRT protocol. We analyzed genomewide DNA methylation of 12 non-treated test samples (T and matched ADJ: 6 each) by methylated CpG island amplification and microarray (MCAM) method (4×44K, Agilent custom array), and selected candidate genes that were highly methylated in T compared to ADJ. We next analyzed DNA mathylation of CYP26C1 (cytochrome P450, family 26, subfamily C, polypeptide 1), one of the candidate genes, in 112 validation samples by quantitative bisulfate pyrosequencing. Results: CYP26C1 was selected by unsupervised hierarchical clustering after MCAM in test samples. CYP26C1 DNA methylation was significantly higher in T than ADJ in both test and validation samples (p<0.04, T: 60.7±7.6, ADJ: 44.5±11.5). Interestingly, some ADJ also showed high methylation in validation samples. Additionally, CYP26C1 methylation in both T and ADJ were significantly depressed after CRT (T: p<0.01 (45.1±18.3 to 31.6±14.9), ADJ: p<0.0001 (43.8±10.3 to 30.5±13.8)). Conclusions: CYP26C1 has a CpG island in promoter area, which is highly methylated in T of ESCC patients. And, some ADJ showed high CYP26C1 methylation, suggesting possibility of multicentric occurrence of ESCC. Moreover, CYP26C1 methylation depress after CRT both T and ADJ, suggesting a new anti-cancer mechanism of CRT through epigenetic alteration. No significant financial relationships to disclose.