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Loss of 17p, mutation of the p53 gene, and overexpression of p53 protein in esophageal squamous cell carcinomas.

We analyzed mutations of the p53 gene by single-strand conformation polymorphism analysis of polymerase chain reaction products and direct sequencing through all coding exons and exon-intron junctions in 32 cases with esophageal squamous cell carcinoma. Mutations were detected in 15 of 32 (47%) tumor samples, in which G:C to T:A transversions were rather frequent (33%). Previously, we reported deletion of chromosome 17p where the p53 gene is located in 45% of Japanese esophageal squamous cell carcinoma, and here the relationship between mutation of the p53 gene and loss of 17p was analyzed. Mutations were observed in 12 of 16 patients with loss of 17p, whereas only 2 of 11 without loss were positive for mutations, suggesting that mutations of the p53 gene were closely associated with a 17p deletion. Furthermore, we immunohistochemically analyzed the expression of p53 protein in esophageal squamous cell carcinoma tumor tissues using a monoclonal antibody. Five of 6 tumors with missense mutations of the p53 gene were positively stained, while in tumors with nonsense mutations or without mutations of the p53 gene staining was very weak or negative. These results suggest a good correlation between mutations and abnormal expression of the p53 gene.