Association between p53 immunostaining and cigarette smoking in squamous cell carcinoma of the esophagus

BACKGROUND: It is generally accepted that cigarette smoking is closely associated with esophageal squamous cell carcinoma. This study investigated the molecular targets of cigarette smoke in carcinogenesis of the esophagus. METHODS: Seventy-four patients with esophageal squamous cell carcinoma (SCC) were grouped according to daily cigarette consumption: heavy smoking group (group H) (n = 26), moderate smoking group (group M) (n = 39) and non-smoking group (group N) (n = 9). We compared p53 and retinoblastoma (RB) expression among the three groups by immunohistochemistry. In addition, fresh tumor tissues from 30 smokers with esophageal SCC were tested for p53 mutations in exons 5-8 by direct sequencing. RESULTS: Staining for the p53 product was positive in 65.4% of group H, 38.5% of group M and 44.4% of group N. The frequency of positive staining in the group H was significantly higher than in group M (p = 0.033) and in group M + group N (p = 0.034). The difference with respect to the frequency of overexpression of RB was not significant. The patterns of p53 base-pair mutations in direct sequencing study were of five types, most commonly G:C to T:A transversion (35.3%). CONCLUSIONS: Our study suggests that one of the molecular targets of cigarette smoke is the p53 gene. The pattern of p53 point mutations involved a wide range of base-pair changes.