Thyroid hormone affects the expression of neoplastic transformation induced by DNA-transfection.

Thyroid hormone can dramatically modulate oncogenic transformation of cells in culture. To further investigate this we have used DNA-mediated gene transfer (transfection) to transform cells grown in the presence (+T3) or absence (-T3) of thyroid hormones. Removal of thyroid hormones from the culture media greatly reduced the appearance of transformed foci subsequent to transfection. However, +T3 or -T3 media had no effect on the appearance of ouabain-resistant (ouar) colonies following transfection of ouabain-sensitive (ouas) cells with DNA isolated from ouar cells and selection in 3 mM ouabain. These results suggest that thyroid hormone does not effect the uptake or integration of exogenous DNA, but instead may modify the expression of transformation.