Inhibitors of protein and RNA synthesis block the cytotoxic effects of non-steroidal antiestrogens
Biochimica Et Biophysica Acta
P L HwangH L Ng
Abstract
Non-steroidal antiestrogens such as tamoxifen are known to exert cytotoxic effects against various cell lines in culture. When the antiestrogens are present at sufficiently high concentrations, their cytotoxicity cannot be reversed by estrogens and is demonstrable even with cell lines which lack the estrogen receptor. The mechanism of this cytotoxicity, which is clearly independent of estrogen antagonism, remains unknown. Using two murine cancer cell lines (the K36 leukemia and the EL4 lymphoma cell line), the human breast cancer cell line MCF7, and two non-steroidal antiestrogens (tamoxifen and clomiphene), our laboratory attempted to determine whether the cytotoxic action of non-steroidal antiestrogens was mediated by a mechanism requiring protein or RNA synthesis. In the case of K36 and EL4 cells, inclusion of tamoxifen or clomiphene in the culture medium regularly caused the viable call count to fall below 20-30% of control in 36-48 h. Under these conditions, the addition of inhibitors of protein or RNA synthesis consistently increased viable cell count in a dose-dependent manner. With cultures of K36 cells grown in the presence of 10 microM tamoxifen, for example, the addition of appropriate concentrations of emetine, cycl...Continue Reading