Cyclic Voltammetry of DNA-mitomycin C Adducts: Comparison of Chemical Reductive Activation of Mitomycin C with other Activation Paths
Anticancer activity of the antibiotic Mitomycin C (MC) is connected with its covalent binding to DNA. It has been shown that a reductive activation of MC, which can take place by a chemical, enzymatic, acid or electrodic process, is necessary for drug bonding to DNA
In this work, chemical activation of MC was made with Na2S2O4 as a reductive agent in buffered media at neutral pH in two conditions: (I) deoxigenated medium at room temperature and fast addition of an excess of Na2S2O4 to MC and (II) non-deoxigenated medium at 0 °C and slow addition of Na2S2O4, because the activation product was dependent on working conditions. The electrochemical technique adsorptive transfer stripping voltammetry (AdTSV) was used and the voltammograms obtained after activation in conditions I and II were unlike one another. They also differed from electrodic and acid activation voltammograms and, furthermore, to the non-activated MC ones. The period of time necessary for chemical activation (in both cases I and II) lay between electrodic activation, practically instantaneous, and acid activation, which required several hours.
Voltammetric behaviour of chemical-activated MC in the presence of native DNA confirms existence of DNA-MC interactions that lead to different adducts after every kind of activation. Chemical activation results can be explained by formation of a bisadduct (conditions I) and a monoadduct (conditions II) respectively, both in the N2-position of guanine bases of DNA, in contrast to acid and electrodic activations which give mono and bisadducts respectively with DNA preferentially in the N(7) position of guanines (where the electroactive group is situated).
The results agree with non-electrochemical researches about these interactions. In conclusion, voltammetric techniques are capable of distinguishing between different adducts and they are therefore a very simple and valuable alternative to studying DNA interactions with substances of biological interest.
C. Teijeiro, A. Di Marino, P. Pérez and D. Marin
Departamento de Química Física, Universidad de Alcalá, 28871