Hanazono 10/8

Mutations of p53, a tumor suppressor gene, are known to be involved in the pathogenesis of a number of neoplasms. This study investigated the distribution of p53 mutations within both esophageal and gastric adenocarcinomas. The correlation between p53 mutations and an overexpression of p53, which has been reported by other researchers, was also explored. Samples were taken from 17 patients following a surgical resection of the tumor. The patients included 8 cases of adenocarcinoma from the cardia (esophagogastric junction) and 9 cases of gastric carcinoma. Two or three samples were taken from each tumor, plus samples of normal tissue from the patient. Denaturing high pressure liquid chromatography (DHPLC) was employed to detect p53 mutations, and samples found to have mutations were then sequenced. The expression of p53 was determined by immunohistochemistry. DHPLC demonstrated that 37.5% (3/8) of esophageal carcinomas and 44.4% (4/9) of gastric carcinomas have p53 mutations. DNA sequencing showed the same mutation to be present in all of the samples from each tumor, while the corresponding normal tissue was free from mutations (except for 2 cases of polymorphism). The results of immunohistochemistry did not demonstrate a relationship between p53 mutations and the expression of p53 protein, and only 4 of the 7 tumors with p53 mutations showed a positive result. These findings support the hypothesis that p53 mutations are homogeneous throughout a tumor and may thus be a more useful diagnostic and prognostic indicator than the expression of p53, which does not reliably correlate with p53 mutations. Introduction Adenocarcinomas of the esophagus and gastric cardia have demonstrated rapidly increasing incidence rates (1). The incidence of adenocarcinoma in the distal esophagus and proximal stomach are rising more rapidly than any other visceral malignancy in the Western industrial world. More than half of all such cases are advanced carcinomas at the time of initial diagnosis, which are associated with a poor 5-year survival rate (2). The p53 gene mutation represents one of the most frequently altered tumor suppressor genes in human cancers (3). p53 mutations have been extensively studied in many tumor types in order to establish the diagnostic, prognostic and therapeutic characteristics of the tumors in which they are associated. A mutation of the p53 gene is a crucial factor in the carcinogenesis of many tumor types (4). Hyperdysplastic epithelial cells in the cardia have also been found to have a high frequency in p53 gene mutations. It is necessary to determine the nature of the mutation in tumor cells, and demonstrate that this mutation occurs homogeneously throughout the tumor tissue, which is an important factor in the characterization of a tumor and selection of the optimal treatment regime. The aim of this study was to investigate p53 gene mutations using several samples obtained from the same tumor specimen. The denaturing high pressure liquid chromatography (DHPLC) technique was used to detect p53 gene mutations in the entire coding region for p53 from exons 5 to 8, the region in which most mutations occur (5). DHPLC is a relatively new technique that uses heteroduplex formations between wild-type and mutated DNA standards to identify mutations. The heteroduplex molecules are separated from homoduplex molecules by ion-pair reverse-phase liquid chromatography on a specialized column matrix, with partial heat denaturation of the DNA strands. DNA sequencing of the mutated gene was performed, and immunohistochemistry was employed to identify any overexpression of the P53 protein. The aim of this study is to test the hypothesis that the same pattern of mutation occurs throughout the cells of an individual tumor and explore whether such a pattern has any relationship with the expression of p53. ONCOLOGY REPORTS 15: 821-824, 2006 821 Distribution of p53 mutations in esophageal and gastric carcinomas and the relationship with p53 expression KOICHI HANAZONO1, SHOJI NATSUGOE1, HUBERT J. STEIN2, TAKASHI AIKOU1, HEINZ HOEFLER3 and J. RUEDIGER SIEWERT2 1Department of Surgical Oncology and Digestive Surgery, Kagoshima University School of Medicine, 8-35-1 Sakuragaoka, Kagoshima, Japan; 2Department of Surgery and 3Institute of Pathology, Klinikum rechts der Isar, Technische Universitaet Muenchen, Ismaninger Str. 22, Munich, Germany Received August 10, 2005; Accepted October 3, 2005 _________________________________________ Correspondence to: Dr Koichi Hanazono, Department of Surgical Oncology and Digestive Surgery, Kagoshima University School of Medicine, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan E-mail: [email protected]