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Hypermethylation of the p14(ARF) gene in ulcerative colitis-associated colorectal carcinogenesis
Fumiaki Sato1, Noam Harpaz, David Shibata
1Gastroenterology Division, Department of Medicine, University of Maryland School of Medicine and Gastroenterology Service, Baltimore, Maryland 21201, USA.
Abstract:
The p14(ARF) protein directly inhibits the MDM-2 oncoprotein, which mediates degradation of the p53 protein. It has been shown that p14(ARF) expression is frequently down-regulated by p14(ARF) gene hypermethylation in colorectal cancer. To determine whether p14(ARF) inactivation was involved in ulcerative colitis (UC)-associated carcinogenesis, the frequency and timing of p14(ARF) methylation was investigated in four different histological stages of UC-associated carcinogenesis. Methylation-specific PCR and bisulfite sequencing were used to determine the prevalence of p14(ARF) gene methylation. p14(ARF) methylation was observed in 19 of 38 (50%) adenocarcinomas, 4 of 12 (33%) dysplasias, and 3 of the 5 (60%) nonneoplastic UC mucosae. In contrast, 3 of 40 (3.7%) normal tissues showed p14(ARF) methylation (chi(2) test: P = 0.0003). Bisulfite sequencing was used to analyze 28 CpGs of p14(ARF) gene in 20 samples. The number of methylated CpGs ranged from 0 to 4, 0 to 20, and 0 to 28 in the normal, dysplastic, and carcinomatous samples, respectively (Kruskall-Wallis test: P = 0.0005). Densely methylated alleles were detected only in carcinomas by bisulfite sequencing. In conclusion, our data suggest that methylation of p14(ARF) is a relatively common early event in UC-associated carcinogenesis. p14(ARF) offers potential as a biomarker for the early detection of cancer or dysplasia in UC. Finally, analyses of p14(ARF) methylation in other organs should explore not only frank cancers but other premalignant lesions.
Insights
p14(ARF) gene methylation is an early event in ulcerative colitis (UC)-associated cancer. This finding suggests p14(ARF) methylation can serve as a biomarker for early detection of dysplasia or cancer in UC patients.
Area of Science:
- Oncology
- Molecular Biology
- Gastroenterology
Background:
- p14(ARF) protein inhibits MDM-2 oncoprotein, regulating p53 stability.
- p14(ARF) gene hypermethylation frequently down-regulates p14(ARF) in colorectal cancer.
- The role of p14(ARF) inactivation in ulcerative colitis (UC)-associated carcinogenesis requires investigation.
Purpose of the Study:
- To investigate the frequency and timing of p14(ARF) gene methylation during UC-associated carcinogenesis.
- To assess the potential of p14(ARF) methylation as an early biomarker for UC-associated cancer.
Main Methods:
- Methylation-specific PCR and bisulfite sequencing were employed.
- p14(ARF) gene methylation was analyzed across normal, nonneoplastic UC mucosa, dysplasia, and adenocarcinoma tissues.
- CpG methylation status within the p14(ARF) gene was quantified.
Main Results:
- p14(ARF) methylation was significantly more frequent in UC-associated neoplastic and nonneoplastic tissues (50% in adenocarcinomas, 33% in dysplasias, 60% in nonneoplastic UC mucosa) compared to normal tissues (3.7%).
- The extent of CpG methylation in the p14(ARF) gene increased progressively from normal to dysplastic to carcinomatous samples.
- Dense methylation of p14(ARF) alleles was predominantly observed in carcinomas.
Conclusions:
- p14(ARF) gene methylation is a common, early event in the development of UC-associated cancer.
- p14(ARF) methylation shows promise as a biomarker for the early detection of cancer or dysplasia in patients with UC.
- Further studies should examine p14(ARF) methylation in premalignant lesions in other organs.