Anti-proliferative effect of toremifene and tamoxifen on estrogen receptor-lacking anaplastic thyroid carcinoma cell lines

The antitumor effects of toremifene were studied in vitro using 10 anaplastic thyroid carcinoma cell lines and were compared with those of tamoxifen. The antitumor effect of toremifene was dose-dependent and the IC50 values for these cell lines ranged 20.1-58.5 microM. Although the cell lines expressed multidrug resistance gene mRNA, multidrug resistance-associated protein gene mRNA and insulin-like growth factor-1 (IGF-1) receptor mRNA to various degrees, nine of them lacked estrogen receptor expression as evaluated by immunocytochemistry. These data indicate that toremifene, as well as tamoxifen, is cytolytic at relatively high doses for multidrug-resistant anaplastic thyroid carcinoma cell lines.