Effects of retinoids and role of retinoic acid receptors in human thyroid carcinomas and cell lines derived therefrom.

: Retinoic acids (RAs), well characterized regulators of proliferation and differentiation, partly re-differentiate follicular thyroid carcinoma cell lines (FTC-133, FTC-238, and HTC-TSHr) as well as SV40-transfected immortalized thyroid cell lines (ori3 and 7751). This is indicated by the stimulation of type I 5'-deiodinase and other differentiation markers. As demonstrated by RT-PCR, electrophoretic mobility shift, and [3H]-retinoic acid binding assays, thyroid carcinoma cell lines express RA receptor mRNAs and functional ligand- and DNA-binding receptor proteins able to mediate RA-dependent signal transduction. Together, these properties make these thyroid-derived cell lines useful in vitro models for studying the effects of an RA re-differentiation therapy of thyroid cancer.