A cyclophosphamide/DNA phosphoester adduct formed in vitro and in vivo

The antitumor activity of cyclophosphamide is thought to be due to the alkylating activity of phosphoramide mustard, a metabolite of cyclophosphamide. Reaction of 2'-deoxyguanosine 3'-monophosphate and phosphoramide mustard resulted in the formation of several adducts that could be detected by high performance liquid chromatography (HPLC). One of these adducts, isolated and purified by HPLC, could be detected by 32P postlabeling. This product was identified by UV, nuclear magnetic resonance, and mass spectrometry and by acid, base, and enzymatic hydrolysis to be 2'-deoxyguanosine 3'-monophosphate 2-(2-hydroxyethyl)aminoethyl ester. A combination of HPLC fractionation of digested DNA and 32P postlabeling was used to detect this adduct in calf thymus DNA incubated in vitro with metabolically activated cyclophosphamide and in DNA from the liver of mice treated with cyclophosphamide. In these DNA samples the adduct occurred at a level of 1/10(5) and 1/3 x 10(7) nucleotides, respectively.