EFFECTS OF 13 CIS-RETINOIC ACID ON GROWTH AND DIFFERENTIATION OF HUMAN FOLLICULAR CARCINOMA-CELLS (UCLA-R0-82-W-1) INVITRO

Dedifferentiation of human thyroid tumors is frequently found in humans. The effect of retinoids (13 cis-RA) was studied on the proliferation and differentiation of a human follicular cell line in vitro (UCLA RO 82 W-l). A significant and dose-dependent reduction (P < 0.001) in cell number and [3H] thymidine uptake was found in cells exposed to 13 cis-RA up to 10 μM. Higher concentrations of 13 cis-RA, however, led to a dose-dependent restoration of cell proliferation. Various parameters of differentiation increased under the influence of 13 cis-RA (10 μM) over nonexposed cells. The 125I uptake increased 4-fold over that in control nonexposed cells (P < 0.05). [12BI] Epidermal growth factor binding increased 5-fold, and [125I] human TSH binding increased significantly after exposure to 13 cis-RA (P < 0.02). Deiodinase activity, however, was significantly lower in 13 /cis-RA exposed cells than in control cells. The present study shows that 13 cis-RA (10 μM) drives the tumor cells toward a more normal state of proliferation and differentiation. © 1990 by The Endocrine Society.