Abstract LB-380: Distinct methylation pattern in early-onset colorectal cancer patients without detectable germline mutation

Colorectal cancer (CRC) is currently the second most common cancer and mortality rate of all cancers in Hong Kong. We have previously reported a higher incidence of early-onset colorectal cancer patients compare with other ethnic groups, which may be caused by genetic or epigenetic predisposition in the Chinese population. Despite we confirmed Lynch Syndrome (LS) plays a significant role in it, pathogenic event of roughly 20% of young patients with MSI tumour cannot be identified. These patients are still susceptible to novel genetic or epigenetic predisposition of CRC. In this study, we compared the epigenetic signature of CRC patients below and above the age of 50 years old, who developed High level of microsatellite instability (MSI-H) and loss of MLH1 expression. The CpG island methylator phenotype (CIMP), regional methylation events, Braf and Kras mutation status have been examined. Among 12 cases of the early-onset patients, unexpectedly 5 of them showed constitutive MLH1 promoter hypermethylation versus 1 in 26 cases of the late-onset control patients by pyrosequencing (p-value Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-380. doi:1538-7445.AM2012-LB-380