P53 EXPRESSION IN NORMAL AND DYSPLASTIC BRONCHIAL EPITHELIUM AND IN LUNG CARCINOMAS

Bronchial epithelial dysplasia is thought to be a premalignant stage i n the evolution of lung cancers. Using the CM-1 polyclonal antibody, w e have examined the expression of the p53 protein in a larger series o f bronchial dysplasias (n = 60) than hitherto investigated. The p53 pr otein was detected in 14% of mild, 25% of moderate and 59% of severe d ysplasias; increased p53 expression correlated with the severity of dy splasia. p53-positive dysplasias had greater PCNA indices than p53-neg ative dysplasias. p53 expression in dysplastic tissues was compared wi th that in two groups of histologically normal epithelium: 14 bronchia l biopsies from non-cancer patients of which all but one were negative and 32 bronchial margins from resected carcinomas, of which 17 showed infrequent solitary cells with p53-positive nuclei in predominantly b asal locations scattered throughout the epithelium. These results for resection margins were confirmed by use of a second antibody, DO-1. Si xty-nine per cent of the corresponding carcinomas were p53 positive, b ut in 15 cases the p53 reactivity differed from resection margins. No correlation between p53 expression and any of the clinicopathological characteristics of these tumours was found. This study supports the ob servation that abnormal p53 expression may be an early but not obligat ory event in malignant transformation in lung.