IntroductionHuman tissue kallikreins (hKs) are secreted serine protéases with diverse expression patterns and physiological rôles. Several members of the kallikrein gène (KLK) family, which now includes 15 gènes, are differentially expressed in various cancers and some émerge as useful diagnostic/ prognostic markers for hormone dépendent cancers. Although clinically effective non-invasive meth-ods for early détection and screening of lung cancer are lacking, analysis of kallikrein gène expression has never been performed in lung. The aim of this study was to investigateKLK5andKLK7gene expression in non small-cell lung cancers (NSCLC).MethodsWe used both RT-PCR and Western blotting to analyseKLK5andKLK7gène expression and their respective products (hK5 and hK7) in lung. Gène expression was then quantified by real-time PCR in matched malignant and nonmalignant lung tissue samples obtained from 56 patients with NSCLC and results were compared to clinico-pathological parameters.ResultsWe detected for the first time the expression of bothKLK5andKLK7gènes and their protein products (hK5 and hK7) in tumoral and nontumoral lung tissues. A significant increase inKLK5expression was observed in squamous cell carcinoma (P = 0.02) compared to matched nontumoral tissue, whereasKLK7expression was decreased in adenocarcinoma (P = 0.003). In non-cancerous tissues, multivariate analysis revealed a négative corrélation betweenKLK5expression and the metastatic status of the paired tumors (P = 0.05) and, a positive corrélation betweenKLK7expression and tumor differentiation (P = 0.02). In cancerous tissues,KLK5andKLK7expressions were mainly associated with squamous cell carcinoma (P = 0.04 and P = 0.01, respectively). Fur-thermore,KLK7expression correlated positively with differentiation (P = 0.03) and negatively with adenocarcinoma histotype (P = 0.003).ConclusionsOur results demonstrate thatKLK5andKLK7are differentially expressed in NSCLC subtypes and indicate that the variability inKLK5andKLK7expressions hâve to be taken into account not only to better understand the lung tumorogenesis but also for clinical purposes.