ROLE OF MDR1 AND P53 EXPRESSION IN THE CH EMORESISTANCE OF LUNG CARCINOMAS

Expression of mdr1 and p53 was assessed on 119 cases of bronchial carc inomas, and compared with clinical chemoresistance, mdr1 expression wa s evaluated by immunohistochemistry (IHC), using the monoclonal antibo dy JSB1. The study of p53 expression was performed by both IHC, using six different antibodies, and Northern blotting. We observed a correla tion 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 corr elation between mdr1 expression and clinical chemoresistance in patien ts with small cell lung carcinoma (SCLC). The frequence of complete re sponse however was significantly higher in patients whose tumor did no express mdr1 (P = 0.02). Chemoresistance correlated well with the phe notype of p53 mutant in SCC (P = 0.015). We conclude that p53 mutation is a better predictive factor of clinical chemoresistance in SCLC tha n mdr1 IHC detection.