Establishment of estrogen receptor-positive transplantable rat thyroid tumor cell lines in vivo

We established 17 transplantable rat thyroid tumor cell lines from the primary thyroid tumor of rats induced by N-bis(2-hydroxypropyl)nitrosamine. Among the 17 tumor cell lines established, only two of them (D1 and G1) were estrogen receptor (ER) positive. These two cell lines were characterized with respect to transplantability, histological features, ER contents and cellular localization, and expression of ER message. The ER contents, determined by dextran-coated charcoal assay, were 13.3 and 20.7 fmol/mg protein for D1 and G1 cell lines, respectively. Scatchard plot analysis indicates that the dissociation constants (Kd) were 0.17 and 0.4 nM, respectively, for D1 and G1 cell lines. Sucrose density centrifugation analysis detected a hormone-receptor complex which sedimented at the 4S region, characteristic for ER. Immunohistological staining revealed that the ER was localized in the nuclei. The presence of ER in D1 and G1 cell lines was further confirmed by reverse transcriptase-polymerase chain reaction to detect the ER mRNA. These results demonstrated that ER is expressed in some thyroid tumors. The ER-positive transplantable tumor cell lines are useful for studying the direct effect of estrogen on thyroid tumors in vitro and in vivo.