TABLE 2
Inhibition of topo I derived from nuclear extracts of murine fibrosarcoma (IC9) tumor cell lines, by tyrphostin derivatives.
For cell cytotoxicity determination, IC9 cells were treated with increasing doses of tyrphostins for 48 h, and cell cytotoxicity was determined by Neutral Red cytotoxicity assay. Topo I activity in the nuclear extracts was measured in the absence or presence of increasing doses of tyrphostins. The results are means ± S.D. of five different experiments. Densitometric analysis was performed, and the IC50 was calculated.