GROWTH-INHIBITION OF HORMONE-RESPONSIVE AND HORMONE-RESISTANT HUMAN BREAST-CANCER CELLS IN CULTURE BY N1,N12-BIS(ETHYL)SPERMINE

Previous studies have documented differential sensitivity of human lung cancer and melanoma cell lines to the cytotoxic effects of N1, N12-bis-(ethyl)spermine (BESpm). We show here that BESpm can significantly inhibit the growth of six human breast cancer cell lines with 50% inhibitory concentration in the muM range. The degree of inhibition does not correlate with estrogen receptor status. Detailed studies with estrogen receptor-positive MCF-7 and estrogen receptor- negative Hs578t cells show a similar dose-response curve with concentrations of 1-10 muM resulting in maximal growth inhibition. Growth inhibition in both lines is associated with an 8-12-fold induction of the polyamine catabolic enzyme, spermidine/spermine N1-acetyltransferase, and a progressive decrease in intracellular polyamine levels over 6 days even though steady-state levels of BESpm are achieved within 24 h. Similar studies on WTMCF7 and Adr(R)MCF7 cells show that the acquisition of resistance to hormonal or doxorubicin therapy is not associated with resistance to the growth-inhibitory effects of BESpm. These results suggest that BESpm exerts similar growth-inhibitory effects against both hormone-responsive and -unresponsive human breast cancer cells, a finding which has significance for the potential use of polyamine analogues in treating human breast cancer.