In vitro DNA crosslinking by Ledakrin, an antitumor derivative of 1-nitro-9-aminoacridine.

Using agarose gel electrophoresis we confirmed that Ledakrin is capable of incurring covalent crosslinking in pBR322 plasmid DNA and also in poly(dGdC) in the presence of a simple activating system containing DTT. The identification of adducts resulting from DNA crosslinking was carried out by 32P-post-labelling assay. We assumed that such adduct(s) should be brought about more readily with double-stranded than with single-stranded polynucleotides or nucleotides. Since our earlier experiments had shown that guanine is a major site of covalent binding of 1-nitroacridines, we compared DNA adduct formation by Ledakrin for ctDNA, dG-containing synthetic homopolymers and 3'-pdG. 32P-Post-labelling assay revealed two adduct spots that were enhanced in samples containing double-stranded substrates in which interstrand crosslinking between guanines was possible, namely ctDNA and poly(dGdC).