EPIDERMAL GROWTH-FACTOR STIMULATES CELL-PROLIFERATION AND INHIBITS IODIDE UPTAKE OF FRTL-5 CELLS IN-VITRO

In accordance with the available data most authors conclude that epide rmal growth factor (EGF) has very Little or no effect on FRTL-5 cells. This has been viewed as a serious handicap of this cell line. In the present study we cultivated three strains of FRTL-5 cells from differe nt sources and assessed their response to EGF with regard to prolifera tion, function and differentiation. Cell proliferation was assessed by counting in a Coulter cell counter after culturing cells at suboptima l conditions in well plates. Cell function was studied by measuring io dide uptake. Cell differentiation was examined immunocytochemically by staining monolayer cultures for thyroglobulin (Tg) and EGF receptor ( EGFr) as well as morphologically by microscopical evaluation of monola yer cultures. AU three FRTL-5 cell lines investigated express EGFr. In two wild type FRTL-5 cell lines EGF stimulates growth, an effect that is enhanced by the presence of TSH, and partially inhibits iodide upt ake. A third mutated strain of FRTL-5 cells does not respond to EGF. T g expression can be demonstrated immunocytochemically in EGF-heated ce lls as well as in controls. Morphologically, in monolayer culture EGF- treated cells cannot be distinguished from controls. Contrary to previ ous reports, these studies demonstrate EGF effects on FRTL-5 cells tha t are consistent with EGF effects established in other thyroid follicu lar cells.