[Respective roles of the products of the mdr1 and p53 genes in drug resistance of bronchial cancers].

Expression of mdr1 and p53 was assessed on 119 cases of bronchial carcinomas, and compared with clinical chemoresistance. mdr1 expression was evaluated by immunohistochemistry (IHC), using the monoclonal antibody JSB1. The study of p53 expression was performed by both IHC, using six different antibodies, and Northern blotting. We observed a correlation between the expression of mdr1 and the presence of a mutation of p53 in neuro endocrine (NE) carcinomas (P = 0.02). Correlation was not observed when non NE carcinomas were evaluated, nor was found any correlation between mdr1 expression and clinical chemoresistance in patients with small cell lung carcinoma (SCLC). The frequency of complete response however was significantly higher in patients whose tumor did no express mdr1 (P = 0.02). Chemoresistance correlated well with the phenotype of p53 mutant in SCC (P = 0.015). We conclude that p53 mutation is a better predictive factor of clinical chemoresistance in SCLC than mdr1 IHC detection.