Effect of fetal thyroid hormone (RT3) on sarcoma cells in culture

Fetal thyroid hormone (RT3) 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, RT3 was found to stimulate the growth of the erythroleukemia cells in culture. The focus of this research was to test the effect of RT3, 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 RT3, ranging from 10(-8)-10(-5) M. Cells grown in serum-free medium containing no RT3 were used as a control. RT3 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 RT3 for any of the concentrations tested. The growth of two Ewing sarcomas and one osteogenic sarcoma was significantly stimulated by RT3 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 RT3 on several sarcoma cell lines in culture suggests the presence of a specific receptor in the neoplastic cells and the possibility that RT3 may be useful as a model for new chemotherapeutic agents.