Immunohistochemical evidence for the overexpression of protein kinase C in proliferative diseases of human thyroid.

We report immunohistochemical evidence for the overexpression of protein kinase C in various proliferative diseases of human thyroid. Immunohistochemical characterization of various surgically removed thyroid tissues, viz., cancer tissues: papillary carcinoma and follicular carcinoma; adenoma tissues: tubular, trabecular and colloid adenomas; adenomatous goiter; and normal thyroid was done using the monospecific monoclonal antibodies MC-1a, MC-2a and MC-3a, each of which is specific for types I, II and III isozymes of protein kinase C, respectively. For protein kinase C type II, a remarkable difference in staining intensity was noted between the cancerous and normal tissues. The cytoplasm of papillary and follicular carcinoma cells stained more intensely than that of normal thyroid cells. In the benign tumor and adenomatous goiter tissues, stronger staining was noted in the papilliform-proliferating portion and cubic epithelial cells. In the normal thyroid tissues, epithelial cells of greater height were more strongly stained than simple squamous epithelial cells. These results indicated that protein kinase C type II isozyme is expressed in larger amounts in cancerous and proliferative tissues of the human thyroid.