New mechanisms of DNA damage and non-covalent DNA binding by the antitumor antibiotic leinamycin

Leinamycin is a natural product with significant anticancer activity, a novel structure, and a unique mechanism of action. It has been previously shown to be capable of both DNA alkylation and oxidative DNA damage. Here we show that thiol-dependent oxidative DNA damage previously observed for leinamycin is a general phenomenon for several other classes of compounds capable of converting thiols to hydrodisulfides.;We have also shown that DNA alkylation by leinamycin does not necessarily have to be thiol-activated. We investigated in detail thiol-independent DNA alkylation by leinamycin and show that it is caused by hydrolytic activation of the antibiotic. We examined relative importance of hydrolytic and thiolytic activation pathways under physiological conditions and at the fate of activated leinamycin under these conditions. We have also demonstrated that leinamycin can be activated by other nucleophiles such as phosphines and cyanide.;Non-covalent binding to DNA can greatly enhance the potency of the DNA-damaging agent. We have shown for the first time that leinamycin and its metabolites are capable of binding to DNA non-covalently. Investigation of DNA binding by synthetic analogs of leinamycin allowed us to pinpoint the DNA-binding portion of the natural product.;In addition, we examined the mechanisms of thiolytic and hydrolytic activation of leinamycin computationally. Ab initio modeling of the reaction of the leinamycin's heterocycle with thiolate and methoxide provided insight into the mechanisms of activation of leinamycin.