Effect of fetal thyroid hormone (RT 3 ) on sarcoma cells in culture

Fetal thyroid hormone (RT 3 ) is considered metabolically inactive and is present in high concentration in fetuses and in some patients with end‐stage malignant disease. In a virus‐induced erythroleukemia cell model, RT 3 was found to stimulate the growth of the erythroleukemia cells in culture. The focus of this research was to test the effect of RT 3 , at several concentrations, on the growth of naturally occurring human sarcomas in cell culture. Cloned cell lines of Ewing sarcoma, rhabdomyosarcoma, and osteogenic sarcoma were grown in multiple flasks of serum‐free medium containing varying concentrations of RT 3 , ranging from 10 −8 and 10 −5 M . Cells grown in serum‐free medium containing no RT 3 were used as a control. RT 3 significantly increased the growth (total protein) of the rhabdomyosarcoma cell line in culture at concentrations between 10 −8 and 10 −6 M , with the maximum effect at 10 −7 M . The growth of one cell line of Ewing sarcoma was not affected by RT 3 for any of the concentrations tested. The growth of two Ewing sarcomas and one osteogenic sarcoma was significantly stimulated by RT 3 but only at the highest concentration of 10 −5 M . The growth of the other osteogenic sarcoma cell line was significantly increased at concentrations of 10 −6 and 10 −7 M . The stimulatory effect of RT 3 on several sarcoma cell lines in culture suggests the presence of a specific receptor in the neoplastic cells and the possibility that RT 3 may be useful as a model for new chemotherapeutic agents.