CHARACTERIZATION OF THYROID MEDULLARY CARCINOMA TT CELL-LINE

TT cell line is the best known stabilized cell line derived from the h uman medullary thyroid carcinoma. The ultrastructural characteristics of these cells include well developed rough endoplasmic reticulum, a p rominent Golgi apparatus and a considerable number of secretory granul es. Numerous hormones were immunocytochemically demonstrated in TT cel ls of which calcitonin and calcitonin gene-related peptide (CGRP) are the products of the same gene but an alternative RNA processing. TT ce lls were found to produce some other hormones as well, namely ACTH, ne urotensin, enkephalin, PTHrP, gastrin-releasing peptide (GRP), seroton in but also functional proteins of the chromogranin group, synaptophys in, NSE, calbindin and tyrosine hydroxylase. Some marker proteins have been detected in the cytosol (CEA) and in the cytoskeleton (alpha-tub ulin, cytokeratin). The influence of numerous factors on the secretory activity of these cells has been demonstrated so far, including effec ts of 1,25-dihydroxycholecalciferol, glucocorticoids, sex steroids, cA MP, gastrin-releasing peptide, sodium butyrate, phorbol esters, ionomy cin and forskolin. The investigators performed on the TT cell line dem onstrate that this is the most reliable model system for the human par afollicular cells developed so far, in comparison to other cell lines derived from the medullary carcinoma of the thyroid.