CATHEPSIN-D IN NORMAL AND NEOPLASTIC THYROID TISSUES

Background. Cathepsin D is a widely distributed lysosomal acidic endop eptidase. It is an estrogen-regulated protein that is a prognostic fac tor in breast cancer. The aim of this study was to measure cathepsin D concentrations in thyroid tissues and to correlate these concentratio ns with clinical and pathologic parameters. Methods. Cathepsin D and t hyroglobulin concentrations were measured in the cytosol of normal thy roid tissues (n = 14), benign nodules (n = 6), and thyroid carcinomas (n = 32) with an immunoradiometric assay. Statistical analysis was bas ed on the Kruskal-Wallis and Wilcoxon tests and on the Spearman rank c orrelation coefficient. Results. The mean level of cathepsin D, expres sed as picomoles per milligram protein minus throglobulin, was higher in the 32 carcinomas, 29.1 +/- 15.5, than in the 14 normal thyroid tis sues, 8.4 +/- 2.5 (p < 0.001) or in the 6 benign nodules, 11.2 +/- 7.3 (p = 0.003). Cathepsin D concentrations correlated with tumor size; S pearman rank correlation coefficient was r(s) = 0.44 (p = 0.012). No s ignificant difference was found regarding histologic type. Cathepsin D concentrations were inversely correlated with the thyroglobulin level in the tumor; Spearman rank correlation coefficient was r(s) = -0.60 (p < 0.001). Conclusions. Cathepsin D concentration is higher in thyro id carcinoma than in normal thyroid tissue, Increased cathepsin D conc entrations correlate with thyroid tumor size but not with histologic t ype. Further studies should be done to confirm the potential prognosti c value of cathepsin D in patients with thyroid carcinomas.