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Array comparative genomic hybridization, expression array, and protein analysis of critical regions on chromosome arms 1q, 7q, and 8p in adenocarcinomas of the gastroesophageal junction

https://doi.org/10.1016/j.cancergencyto.2008.08.018Get rights and content

Abstract

Survival rates of adenocarcinomas of the gastroesophageal junction (GEJ) are low, because these tumors are generally in an advanced stage by the time they are detected. Chromosomal regions 1q32, 7q21, and 8p22 display critical alterations in GEJ cancers; however, the genes underlying alterations in these genomic areas are largely unknown. To delineate overexpressed genes, we performed array comparative genomic hybridization (aCGH) and mRNA expression analysis of 15 GEJ adenocarcinoma samples using a fine-tiling cDNA array covering chromosome segments 1q31.3∼q41 (193.9–215.8 Mb: 21.9 Mb), 7q11.23∼q22.1 (72.3–103.0 Mb: 30.7 Mb), and 8p23.1∼p21.3 (11.1–20.7 Mb: 9.6 Mb). Based on a mRNA overexpression criterion, 11 genes were selected: ELF3 and SLC45A3 on 1q; CLDN12, CDK6, SMURF1, ARPC1B, ZKSCAN1, MCM7, and COPS6 on 7q; and FDFT1 and CTSB on 8p. The protein expression levels were subsequently determined by immunohistochemical analysis of the cancer samples. There was a significant correlation between genomic amplification, mRNA, and protein expression or overexpression for CDK6, a cell cycle regulator on 7q21.2 (92.1 Mb; P < 0.01); other genes showed less stringent associations. In conclusion, using a straightforward approach we constructed a targeted gene profile for GEJ adenocarcinomas.

Introduction

Adenocarcinomas in Barrett's esophagus are generally in an advanced stage at the time of detection, and the reported overall 5-year survival rates are only 10-20% [1], [2]. Reflux disease has been suggested to be the most important etiological factor in the development of gastroesophageal junction adenocarcinomas. In the esophagus, long-standing reflux disease can result in Barrett's esophagus, in which squamous cell epithelium has undergone metaplastic change to columnar epithelium. Barrett's esophagus is associated with a highly increased risk of developing adenocarcinoma [3]. Metaplastic change has also been observed at the gastroesophageal junction and in the gastric cardia [4], [5].

Gastroesophageal junction adenocarcinomas have been characterized in several genome-wide comparative genomic hybridization studies. Gains were detected most frequently at 1q, 3q, 6p, 7p, 7q, 8q, 17q, and 20q; recurrent losses were found at 4p, 4q, 5q, 8p, 9p, 17p, and 18q [6], [7], [8], [9], [10], [11], [12], [13] Gene amplification in esophageal adenocarcinomas has been investigated by molecular methods [14]. The gene most commonly amplified was ERBB2, on chromosome 17q12. Next are a number of other genes, including MET, EGFR, and MYC. Comparative genomic hybridization (CGH) with a commercial DNA array comprising 287 cancer-related DNA targets showed frequent amplification of several genes [15].

Recently, we reported that gain of 1q32 and loss of 8p22 are associated with progressive cancer behavior (i.e., recurrence-free period or lymphatic dissemination) in early stage esophageal adenocarcinomas [16] and we reported the frequent amplification of 7q21 in gastroesophageal junction cancers [17]. The genes underlying these aberrant regions, however, had not been detected. Our objective, therefore, was to identify these critically altered genes using straightforward and robust approaches.

Section snippets

Tumor samples

The study material comprised 11 fresh-frozen tumor specimens (from 10 men and 1 woman; mean age, 63.2 years): 8 Barrett-related adenocarcinomas of the esophagus and 3 cancers of the proximal stomach cancers (gastric cardia). In addition, cell lines OE19, OE33, M5.1, and SKGT-4 were investigated. Three of these cell lines were derived from esophageal adenocarcinomas and one from and gastric cardia. Barrett-related adenocarcinomas were clearly located in the distal esophagus in the presence of

Results and discussion

We performed genomic and expression analyses of critical chromosomal regions on 15 selected gastroesophageal junction adenocarcinomas: 11 primary adenocarcinomas and 4 cell lines. Eleven of these cancers were esophageal (Barrett-related), 4 originated from the gastric cardia. The primary adenocarcinomas comprised 3 TNM stage I, 4 stage II, 2 stage III and 2 stage IV tumors. We applied array comparative genomic hybridization (aCGH) and mRNA expression analysis using a custom-made fine-tiling

Acknowledgments

This work was supported by the Dutch Cancer Society (grant DDHK 2002-2700).

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    Current address: Department of Pathology, Sint Lucas Andreas Hospital, P.O. Box 9243, 1006 AE Amsterdam, The Netherlands.

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