Cathepsin D expression in early cutaneous malignant melanoma

Background The aspartic proteinase cathepsin D is believed to be associated with proteolytic processes leading to the invasion and seeding of tumor cells. An association between cathepsin D tissue concentration and aggressiveness of tumors has been detected in different cancer types, as well as in metastatic melanoma. Methods The concentration of cathepsin D was measured immunoradiometrically (ELSA-CATH-D kit, CIS Bio International) in the cytosols of 51 primary cutaneous melanomas (with Breslow index 44 mm) to estimate the tissue concentrations of cathepsin D in early cutaneous melanoma. Results A significantly elevated concentration of cathepsin D was measured in the tumor cytosols as compared to adjacent normal tissue (44.2 vs. 14.7 pmol/mg of total protein, P<0.001). Conclusions Our results indicate that cathepsin D is expressed at high levels by melanoma cells. The extremely high expression of cathepsin D in two of our patients, with later progression of the disease over a 42-month follow-up period, suggests a possible correlation between the cathepsin D tissue concentration and the prognosis of primary cutaneous malignant melanoma.