Interaction of 4'-(9-acridinylamino)methanesulfon-m-anisidide with DNA and inhibition of oncornavirus reverse transcriptase and cellular nucleic acid polymerases.

4'-(9-Acridinylamino)methanesulphon-m-anisidide (AMSA) (NSC 141549), an acridine derivative with activity against a variety of laboratory tumors in vivo, is presently undergoing Phase 1 clinical evaluation. The interaction of AMSA with DNA and its effects on nucleic acid-polymerizing enzymes were examined in an attempt to define the site of cytotoxicity of AMSA. Binding of AMSA to DNA, as demonstrated by equilibrium dialysis and spectrophotometric methods, appears to be similar to other aminoacridines, in that two types of binding sites (type 1 and type 2) were observed. Fluorescence studies and thermal denaturation studies gave strong evidence that AMSA type 1 binding was by intercalation into DNA. The binding of AMSA to DNA was without marked base-pair specificity. Furthermore, the effect of AMSA on nucleic acid-polymerizing enzyme activities (mouse embryo DNA polymerase alpha, avian myeloblastosis virus reverse transcriptase, and Escherichia coli RNA polymerase) was studied. Inhibition of enzyme activity by AMSA appeared to be independent of DNA base sequence. The relatively high concentrations of AMSA required for inhibition of these enzymes as compared to the concentrations of AMSA necessary for cytotoxicity in vitro suggest that the interaction with DNA alone might not fully explain its antitumor activity.