Implications of enzymatic, acidic and thermal hydrolysis of DNA on the occurrence of cross-linked melphalan DNA adducts

Abstract Calf thymus DNA was treated with melphalan, a nitrogen mustard, and the formation of melphalan cross‐linked DNA adducts was investigated. These cross‐linked adducts could not be detected either in the enzymatically or in the thermally generated DNA hydrolysates. However, a search for DNA cross‐linked adducts in the hydrolysates obtained under acidic conditions revealed the presence of different types of cross‐links, mainly containing an adenine moiety. These results are very important because they show that the detection of cross‐links is dependent on the hydrolytic procedure used and that these cross‐linked adducts are formed under totally different reaction conditions from those in in vivo situations. This can explain the very low abundance or even the absence of cross‐linked adducts in nitrogen mustard treated animals. The generally accepted theory that the anti‐cancer activity of bifunctional mustards such as melphalan is due to cross‐linking of DNA strands remains therefore from our point of view questionable. Copyright © 2005 John Wiley & Sons, Ltd.