Enzymatic and ultrastructural study of lysosomes in rats bearing radiation-induced thyroid follicular carcinoma

[Changes in active cysteine cathepsins in lysosomes from tissues thyroid papillary carcinomas with various biological characteristics]

To clarify possible role of cysteine cathepsin H, B and L in the proteolytic processes that contribute to the progression of tumor growth in the thyroid, we studied their activity in lysosomes isolated from the tissue of papillary carcinomas. It was shown that for these enzymes there is a dependence of the changes in their activity on a number of biological characteristics of the tumors. Thus, the sharp increase in the activity ofcathepsin H observed in lysosomes of tissue carcinomas category T2 and T3, with intra-and ekstrathyroid and lymphatic invasion of tumor cells. An increase in the activity of cathepsin B is set in the lysosomes of tissue heterogeneous follicular structure, especially in the presence of solid areas, in comparison with typical papillary tumors and in the lysosomes of tissue carcinomas in intrathyroid and cathepsin L-at extrathyroid invasion. A common feature of the enzymes is to increase the activity of cathepsins in lysosomes of tissue nonencapsulated papillary carcinomas. These enzymes probably do not take part in the invasion of tumor cells into blood vessels and in the mechanisms of tumor metastasis to regional lymph nodes. The latter shows no changes in the activity of cathepsins in lysosomes of tissue carcinomas category N1. The results indicate the different role of cathepsin H, B and L in thyroid carcinogenesis, where each enzyme has its specific function.

Acid thyroglobulin protease activities in human diseased thyroid glands

The lysosomal acid protease is thought to be a main enzyme in hydrolysis of thyroglobulin. The protease activity of lysosome-rich fractions of various diseased thyroid glands were assayed by the sensitive and reproducible method developed in our laboratory. They included 78 diseased thyroid glands; 37 thyrotoxic goitres, five irradiated thyroids, five Hashimoto's thyroiditis, one granulomatous thyroiditis, six multinodular goitres, 14 'cold' adenomas, four 'hot' adenomas with three paranodular tissues, and six carcinomas. Fifteen paranodular tissues of cold and solitary thyroid nodules were served as controls. The protease activities were significantly increased in thyroid tissues of thyrotoxic goitres, Hashimoto's thyroiditis, adenomas and adenocarcinomas. In thyrotoxic goitres, the protease activity correlated well with the mean area size of colloid follicles. The 'hot' adenomas had higher protease activity than 'cold' ones. The protease activity of multinodular goitres was nearly normal. Only the irradiated thyroid glands had low protease activities. Therefore the high protease activities in hyperfunctioning goitres seem to reflect hormone secretory activities. On the other hand, cold neoplastic goitres seem to have lysosomal protease activities which are not associated with thyroidal secretory process. The assay of acid protease activity will be useful to understand the pathophysiology of lysosomal system in diseased thyroid glands.