A phenotypically and karyotypically stable human thyroid epithelial line conditionally immortalized by SV40 large T antigen.

Primary cultures of normal human neonatal thyroid follicular cells were transfected with a plasmid expressing a temperature-sensitive (tsA58) mutant of SV40 large T antigen. An epithelial cell line, designated B-thy-ts.1, was obtained which showed tight temperature-dependent growth. In sharp contrast to previous such lines, which were derived from adult thyroid, B-thy-ts.1 has retained a well-differentiated phenotype as reflected in its morphology and cytokeratin expression pattern. In addition to phenotypic stability the line also displays an unusually stable karyotype, lacking the usual clastogenic effects of SV40, which we speculate to result from a greater DNA repair capacity of its cell of origin. B-thy-ts.1 should be a particularly useful tool with which to study the effects of activated oncogenes on epithelial growth and differentiation.