MECHANISM OF THE INHIBITION OF CELL-GROWTH BY N1,N12-BIS(ETHYL)SPERMINE

The mechanism of the antiproliferation effect of N1, N-12-bis(ethyl)spermine (BESPM) was studied in detail using mouse FM3A cells, since this polyamine analogue mimics the functions of spermine in several aspects [Igarashi, K., Kashiwagi, K., Fukuchi, J., Isobe, Y., Otomo, S. & Shirahata, A. (1990) Biochem. Biophys. Res. Commun. 172, 715 - 720]. Our results indicate that not only the decrease in sperimine and spermine caused by BESPM but also its accumulation play important roles on the inhibition of cell growth by BESPM, since BESPM accumulated in cells at a concentration fivefold that of spermidine in control cells. In comparison with the polaymine-deficient cells caused by alpha-difluoromethylornithine, an inhibitor of ornithine decarboxylase, and ethylglyoxal bis(guanylhydrazone), an inhibitor of S-adenosylmethionine decarboxylase, the behavior of polyamine-deficient cells caused by BESPM was different as follows: the inhibition of cell growth by BESPM was not abrogated by spermine or spermidine; polyamine uptake, which is stimulated during polyamine deficiency, was greatly inhibited, while spermidine/spermine N1-acetyltransferase activity, which is inhibited during polyamine deficiency, was enhanced in BESPM-treated cells; thymidine kinase activity did not decrease in BESPM-treated cells; inhibition of cell growth and macromolecule synthesis by BESPM correlated with the swelling of mitochondria and the decrease in ATP content; BESPM caused cell death when incubated together for several days. The role of BESPM accumulation on inhibition of cell growth is discussed.