CORRELATION OF CYTOTOXICITY AND PROTEIN-ASSOCIATED DNA STRAND BREAKS FOR 2-(ARYLMETHYLAMINO)-1,3-PROPANEDIOLS

A mechanism of action study was performed with 14 novel DNA binding ag ents characterized structurally as 2-(arylmethylamino)-1,3-propanediol s (AMAPs). Correlations between 8226 myeloma cell colony formation and DNA damage were performed using soft agar colony-forming assays and a lkaline elution filter techniques respectively. The frequency of doubl e-stranded breaks (DSBs), single-stranded breaks (SSBs) and DNA-protei n cross-links were compared with cell growth inhibitory potency. Highl y potent AMAPs in the colony formation assays included 91U86, an N-met hyl-5-benzo(c)carbazole derivative, 773U82, a 3-substituted fluoranthe ne derivative, and crisnatol (770U82), the 6-substituted chrysene deri vative. There was a high frequency of SSBs and DSBs with many analogue s, but only SSBs occurred in a concentration-dependent fashion. Using regression analysis, the degree of single-strand damage correlated wit h cytotoxic potency for the AMAPs, with an R-value of 0.57 (P = 0.04). By gel electrophoresis assays, three clinically tested AMAPs, crisnat ol BW 770U82, BW 502U83 and BW 773U82, were shown to inhibit the decat enation of pBR 322 DNA by purified topoisomerase-II (TOPO-II) enzymes. These results suggest that while some active AMAPs, such as crisnatol (BW 770U82), BW 502U83 and BW 773U82, inhibit TOPO-II enzymes, leadin g to protein-associated SSBs, other mechanisms, which do not involve D NA strand damage, must also contribute to the cytotoxic effects of thi s class of antitumor compounds. Intercalation has been well documented for these drugs and this may explain some of the growth inhibitory ac tivity of the AMAPs.