Inhibition of growth of breast cancer cells in vitro by the ribosome-inactivating protein saporin 6.

The antiproliferative activity of Saporin 6, a Ribosome-inactivating protein purified from the seeds of Saponaria officinalis has been tested on human breast cancer cells in vitro by the analysis (a) of colony formation in cells from surgical specimens from 27 patients bearing primary breast cancer and (b) of protein synthesis inhibition in the MCF/7 cell line. Results indicate a very high sensitivity of breast cancer cells from most patients to a short-term treatment with Saporin 6 at concentrations (10(-9) M), until now found effective only in acellular systems or after conjugation with monoclonal antibodies. On the contrary, the treatment of the human cell line MCF/7 indicate a very reduced sensitivity compared to fresh human neoplastic cells, with the necessity of a long lag for the effect to begin.