HUMAN-MALIGNANT THYROID-TUMORS DISPLAYED REDUCED LEVELS OF TRANSFORMING-GROWTH-FACTOR BETA-RECEPTOR TYPE-II MESSENGER-RNA AND PROTEIN

Transforming growth factor beta (TGF-beta) is a physiological regulato r of thyroid epithelial cell growth and differentiation. This factor s ignals through a heteromeric complex composed of type I (TGF-beta rece ptor type I) and type II [TGF-beta receptor type II (T beta RII)] rece ptors, Loss of T beta RII expression has been related to resistance to TGF-beta inhibition of cell proliferation, In the present work, we an alyzed the T beta RII expression in a series of human thyroid tumors, from benign lesions (adenomas) to neoplastic lesions of increasing agg ressiveness (papillary and follicular carcinomas) up to the extremely aggressive anaplastic tumors, Results obtained indicated a clear reduc ed expression of T beta RII mRNA only in the group of thyroid carcinom as when compared with their relative normal tissues, Immunohistochemic al analyses with specific anti-T beta RII antibodies confirm these obs ervations, These data indicate that loss of expression of T beta RII c an contribute to thyroid cancer progression, inducing cancer cells to escape the growth-inhibitory effect of TGF-beta.