Chemistry and biology of deoxynyboquinone, a potent inducer of cancer cell death

Deoxynyboquinone (DNQ) is a potent antineoplastic agent with an unknown mechanism of action. Here we describe a facile synthetic route to this anthraquinone, and we use this material to determine the mechanism by which DNQ induces death in cancer cells. DNQ was synthesized in seven linear steps through a route employing three palladium-mediated coupling reactions. Experiments performed on cancer cells grown in hypoxia and normoxia strongly suggest that DNQ undergoes bioreduction to its semiquinone, which then is re-oxidized by molecular oxygen, forming superoxide that induces cell death. Furthermore, global transcript profiling of cells treated with DNQ shows elevation of transcripts related to oxidative stress, a result confirmed at the protein level by Western blotting. In contrast to most other antineoplastic agents that generate reactive oxygen species (ROS), DNQ potently induces death of cancer cells in culture, with IC₅₀ values between 16 and 210 nM. In addition, unlike the experimental therapeutic elesclomol, DNQ is still able to induce cancer cell death under hypoxic conditions. This mechanistic understanding of DNQ will allow for a more comprehensive evaluation of the potential of direct ROS generation as an anticancer strategy, and DNQ itself has potential as a novel anticancer agent.