An investigation into the formation of N-[2-(dimethylamino)ethyl]acridine-4-carboxamide (DACA) and 6-[2-(dimethylamino)ethylamino]-3-hydroxy-7H-indeno[2,1-c]quinolin-7-one dihydrochloride (TAS-103) stabilised DNA topoisomerase I and II cleavable complexes in human leukaemia cells

The antitumour agents DACA (XR5000; N-[2-(dimethylamino)ethyl]acridine-4-ca rboxamide) and TAS-103 (6-[2-(dimethylamino)ethylamino]-3-hydroxy-7H-indeno [2,1-c]quinolin-7-one dihydrochloride) have been shown to inhibit two essen tial nuclear enzymes in vitro, DNA topoisomerase I and DNA topoisomerase (t opo) II. To examine whether DACA or TAS-103 stabilise topo I, topo II alpha , and topo II beta cleavable complexes in human leukaemia CCRF-CEM cells, t he TARDIS assay ((t) under bar rapped in (a) under bar ga (r) under bar ose (D) under bar NA immuno (s) under bar taining) was used. This assay can re veal drug-stabilised topo-DNA complexes formed in situ in individual cells. The results showed that both DACA and TAS-103 can stabilise topo II alpha cleavable complexes in these cells. Topo II beta cleavable complexes were a lso formed, but only at high concentrations of DACA and TAS-103. The effect on topo I was less clear, with TAS-103 showing only low levels of cleavabl e complex formation and DACA having no detectable effect under these assay conditions. This is in contrast to the purified enzyme cleavable complex as say, where both DACA and TAS-103 poisoned topo I. Although both DACA and TA S-103 show a preference for topo II alpha in whole cells using the TARDIS a ssay, the formation of low levels of topo I or topo II beta cleavable compl exes may still play a role in cell death. (C) 2000 Elsevier Science Inc.