Promoter hypermethylation inactivate tumour suppressor FAM134B and is associated with poor prognosis in colorectal cancer

Abstract

The present study aims to examine promoter methylation status of FAM134B in a large cohort of patients with colorectal adenocarcinomas. The clinical significances and correlations of FAM134B promoter methylation with its expression are also analysed. Methylation-specific high-resolution melt-curve analysis followed by sequencing was used to identify FAM134B promoter methylation in colorectal adenomas (n=32), colorectal adenocarcinomas (n=164), matched adjacent non-neoplastic colorectal mucosae (n=83) and colon cancer cell lines (n=4). FAM134B expression was studied by real-time quantitative polymerase chain reaction, immunohistochemistry, and Western blots. FAM134B promoter methylation was more frequent in adenocarcinomas (52%; 85/164) when compared to that of adenomas (28%; 9/32) and non-neoplastic mucosae (35%; 29/83). Cancer cells exhibited higher methylation when compared to non-neoplastic cells. FAM134B promoter methylation was inversely correlated with low FAM134B copy number and mRNA/protein expressions, whereas in-vitro demethylation has restored FAM134B expression in colon cancer cells. FAM134B promoter methylation was associated with high histological grade (p = 0.025), presence of peri-neural infiltration (p = 0.012), lymphovascular invasion (p = 0.021), lymph node metastasis (p = 0.0001), distant metastasis (p = 0.0001) and advanced pathological stages (p = 0.0001). In addition, FAM134B promoter methylation correlated with cancer recurrence and poor survival rates of patients with colorectal adenocarcinomas. To conclude, FAM134B promoter methylation plays a key role in regulating FAM134B expression in-vitro and in-vivo, which in turn contributes to the prediction of the biological aggressiveness of colorectal adenocarcinomas. Furthermore, FAM134B methylation might act as a marker in predicting clinical prognosis in patients with colorectal adenocarcinomas. This article is protected by copyright. All rights reserved.

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