Hypermethylation of hMLH1, HPP1, p14^ARF, p16^INK4A and APC in primary adenocarcinomas of the small bowel

Abstract

Small bowel adenocarcinoma (SB-AC) is a very rare tumor entity. Epigenetic alterations, including hypermethylation of DNA mismatch repair genes and tumor suppressor genes, seem to be important for carcinogenesis in tumors of the gastrointestinal tract, but have not yet been investigated in SB-AC. In the current study, the prevalence of hypermethylation in a panel of genes involved in gastrointestinal carcinogenesis (hMLH1, HPP1, p14 ARF , p16 INK4A , APC) was determined in a series of SB-AC. Paraffin-embedded tumor samples from 56 patients with SB-AC who underwent surgical resection between January 1985 and December 2003 were investigated for hypermethylation by means of methylation-specific real-time PCR, and compared with our findings in a previously investigated series of 50 gastric adenocarcinomas. In comparison with adenocarcinomas of the stomach, SB-AC revealed a significantly higher rate of hypermethylation of HPP1 (86% versus 54%, p 5 0.0003), p16 INK4A (32% versus 10%, p 5 0.0006), and a significantly lower rate of hypermethylation of APC (48% versus 84%, p 5 0.0001). Hypermethylation of hMLH1 and p14 ARF was present in 23% and 9% of SB-AC, respectively. Locally advanced tumor categories (pT3/4) showed a higher rate of hypermethylation of HPP1 (90%) than did early tumor categories (pT1/2 categories, 40%; p 5 0.0036). This was also reflected by the correlation between the HPP1 hypermethylation and high UICC stage (p 5 0.02). No correlation was found between hypermethylation and other clinicopathologic parameters such as age, tumor grade and nodal status. Our findings suggest that hypermethylation of hMLH1, HPP1, p16 INK4A and APC is frequent in primary adenocarcinomas of the small bowel. The differences in the hypermethylation spectrum of small bowel and stomach cancer indicate significant epigenetic differences between these tumors. ' 2006 Wiley-Liss, Inc.Key words: small bowel carcinoma; hypermethylation; methylationspecific real-time PCR; gastric cancer Primary adenocarcinomas of the small bowel (SB-AC) are rare. 1-3 Surgeons and physicians are challenged by this tumor because of its infrequency, unspecific symptoms and typically delayed diagnosis. 1,3-5 Prognostic factors are the residual tumor (R category), tumor stage according to the UICC, lymph node metastasis, lymphatic vessel invasion and vascular invasion. [4][5][6] Mucosal contact time with bile acid solutions seems to be one important factor in the development of adenocarcinoma of the small bowel, 7 implicating bile as a potential carcinogen. Other predisposing conditions are small bowel adenomas, familial adenomatous polyposis, celiac disease, cystic fibrosis, peptic ulcer disease 8 and Crohn's disease. 9 Cases occurring in association with ulcerative colitis and backwash ileitis have also been described. 10 An important epigenetic mechanism for silencing tumor suppressor genes during carcinogenesis is the hypermethylation of CpG islands. 11 In certain cancer types, such as colorectal and endometrial cancers, loss of function of the DNA mis...

High-Resolution Array Comparative Genomic Hybridization in Sporadic and Celiac Disease–Related Small Bowel Adenocarcinomas

“…This prompted us to investigate the mutation and promoter methylation status of the tumor suppressor gene APC (5q21-q22). Mutations in the MRC region of the APC gene were five times more common in non-celiac diseaserelated small bowel adenocarcinomas, whereas APC promoter hypermethylation was found much more frequently in celiac disease-related small bowel adenocarcinomas, which is in concordance with previous studies (13,18,34,49). The APC mutation and methylation status in small bowel adenocarcinoma are in contrast to the results reported in colorectal cancer in which 60% to 80% of the tumors show nonsense mutations of the MRC region and only 20% to 30% display promoter hypermethylation (50,51).…”

“…Fifteen to twenty percent of small bowel adenocarcinomas show microsatellite instability (8,14), and patients with microsatellite-unstable small bowel adenocarcinomas seem to have a better prognosis than patients with microsatellite stable tumors (15). Several studies have also documented mutations of SMAD4, APC, KRAS, and β-catenin (13,(16)(17)(18), as well as epigenetic silencing of APC and gains on chromosomes 7, 8, 12, 13q, and 20q, and losses on chromosomes 2, 4, 5q, 6q, 8, 9, 15q, 17p, 18, and 21 (19,20). Studies evaluating the chromosomal aberrations in patients with concomitant small bowel adenocarcinoma and Crohn's disease or familial adenomatous polyposis have shown that the chromosomal aberrations of sporadic small bowel adenocarcinoma do not differ from patients with these predisposing conditions (19,20).…”

Epigenetic instability is rare in fibrolamellar carcinomas but common in viral-associated hepatocellular carcinomas

“…HPP1 has been previously reported to be methylated in adenocarcinomas from the esophagus, stomach, small bowel and colorectum. [26][27][28][29][30][31] A previous study found HPP1 to be downregulated in fibrolamellar carcinomas at the mRNA level 10 and the current results demonstrate that the downregulation of HPP1 expression is associated with promoter methylation. The function of this gene is unknown; however, it codes for a transmembrane protein that contains both epidermal growth factor and follistatin-like domains and may play a role in inhibiting serine proteases.…”

Chromosomal and methylation alterations in sporadic and familial adenomatous polyposis-related duodenal carcinomas

“…Usually, aberrant methylation of normally unmethylated CpG-rich areas, also known as CpG islands, which are located in the promoter regions of genes, have been associated with transcriptional inactivation of important tumor suppressor genes, DNA repair genes or metastasis inhibitor genes. 18,19 Until now, only a few reports have been published on chromosomal changes or methylation of DNA with respect to the carcinogenesis of the small intestine, [20][21][22][23] which lead us to use global screening methods in this study. Comparative genomic hybridization (CGH) enables detection of chromosomal gains and loses, and can be applied to fixed tissue samples.…”