Induction of 2'-5' oligoadenylate synthetase and activation of ribonuclease in tamoxifen treated human breast cancer cell lines.

In the present study the intracellular activity of oligoadenylate synthetase and ribonuclease have been evaluated in two human breast cancer cell lines treated with tamoxifen, a well known antiestrogenic drug. Increased levels of oligoadenylate synthetase and enhanced ribonuclease activity have been found in the cultures of CG5 cell line treated with concentrations of tamoxifen inhibiting cell growth. In the experiments with the EVSA-T cell line we found neither an antiproliferative effect nor an increased oligoadenylate synthetase and ribonuclease activity. It is likely that these enzymes are involved in the mechanisms by which this drug acts as an antiproliferative agent.