Clinical Cancer Research, Vol 2, Issue 3 561-568, Copyright © 1996 by American Association for Cancer Research

ARTICLES

Cathepsins D, B, and L in malignant human lung tissue

P Ledakis, WT Tester, N Rosenberg, D Romero-Fischmann, I Daskal and TT Lah
Department of Pathology and Laboratory Medicine and Cancer Center, Albert Einstein Medical Center, Philadelphia, Pennsylvania 19141, USA.

The levels of cathepsins in malignant and surrounding nonmalignant lung tissue were determined in 17 non-small cell lung cancer specimens. Cathepsin (Cat) D activity was assayed using hemoglobin, whereas Cat B and Cat L activities were assayed using fluorimetric substrates, benzoylcarbonyl-Ala-Arg-Arg-7-amino-4-methylcoumarine and benzoylcarbonyl-Phe-Arg-7-amino-4-methylcoumarine, respectively. Cat protein concentrations were determined using ELISAs. In malignant tissues, the activities of Cat B and Cat L were significantly higher than the activities in nonmalignant tissues (P < 0.0012 and P < 0.0003, respectively), whereas Cat D concentration was not. There was also a 5.6-fold increase in median Cat B protein (P < 0.054) and a 2.2-fold increase in Cat L protein (P < 0.069). By contrast, the aspartic proteinase, Cat D protein, was not significantly increased in tumors versus control lung tissues. Moderate but significant correlation (r = 0.5, P < 0.045) between Cat B and Cat L expression was observed, but neither correlated with Cat D. The relative increase in median Cat L activity (P < 0.037) and protein (P < 0.0005) was greater in poorly differentiated tumors than in moderate ones. Cat L activity (P < 0.003) and protein (P < 0. 005) increases were higher in adenocarcinoma than in squamous cell carcinoma. We conclude that in lung cancers the three lysosomal enzymes are regulated in a noncoordinate manner and that there is specific induction of cysteine cathepsins. Whether Cat B and/or Cat L would be of diagnostic and/or prognostic value requires further study in a larger patient population.

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