Sa1926 Mucin O-Glycans As Potential Prognosis and Recurrence Markers of Colorectal Cancer

Abstract

Background Micro-array analysis of promoter hypermethylation provides insight into the role and extent of DNA methylation in colorectal cancer (CRC) development, and allows direct comparison with DNA mutations. Methods Colonic biopsy samples were obtained endoscopically from 10 normal, 23 adenoma (17 low grade (LGD) and 6 high grade dysplasia (HGD)), and 8 ulcerative colitis patients. CRC samples were obtained from 24 patients (17 primary, 7 metastatic (mCRC)). Field effects were analyzed in tissues 1cm(n=5) and 10cm(n= 5) from CRC margins. Tissue materials were analyzed for DNA methylation status using a 96 gene panel and expression levels were assayed using whole genomie mRNA arrays. SFRP1 was examined by immunohistochemistry. 5-aza treatment was performed on HT29 cells to analyze reversal of DNA methylation. Results 10 genes (including SFRP1, MAL, SLIT2, SEPTIN9) showed hypermethylation in more than 85% of tumor samples. The number of methylated gene alterations were: HGD(56) > LGD(40) > CRC(37) > mCRC(12). 2 genes (MAL and SFRP1) distinguished precancerous and cancerous lesions from inflammed and healthy tissue (p<0.05). Methylation influenced mRNA and protein expression. The mRNA alteratons caused by the systematic methylation could be reversed by demethylation treatment. Conclusion Systematic changes in methylation patterns were observed early in CRC carcinogenesis, occuring in precursor lesions and all classes of CRC, often prior to the appearance of sporadic mutations. DNA hypermethylation is an early and systematic event reflected in mRNA and protein alterations in colorectal carcinogenesis, and can be potentially reversed by systematic demethylation therapy.