Transforming growth factor β (TGF-β) is a physiological regulator of thyroid epithelial cell growth and differentiation. This factor signals through a heteromeric complex composed of type I (TGF-β receptor type I) and type II [TGF-β receptor type II (TβRII)] receptors. Loss of TβRII expression has been related to resistance to TGF-β inhibition of cell proliferation. In the present work, we analyzed the TβRII expression in a series of human thyroid tumors, from benign lesions (adenomas) to neoplastic lesions of increasing aggressiveness (papillary and follicular carcinomas) up to the extremely aggressive anaplastic tumors. Results obtained indicated a clear reduced expression of TβRII mRNA only in the group of thyroid carcinomas when compared with their relative normal tissues. Immunohistochemical analyses with specific anti-TβRII antibodies confirm these observations. These data indicate that loss of expression of TβRII can contribute to thyroid cancer progression, inducing cancer cells to escape the growth-inhibitory effect of TGF-β.
This work was supported by the Associazione Italiana Ricerca sul Cancro and by Progetto Finalizzato Applicazoni Cliniche della Ricerca Oncologica of the Consiglio Nazionale delle Ricerche. G.M. was supported by an Associazione Italiana Ricerca sul Cancro Fellowship.