Discovery of Nonquinone Substrates for NAD(P)H: Quinone Oxidoreductase 1 (NQO1) as Effective Intracellular ROS Generators for the Treatment of Drug-Resistant Non-Small-Cell Lung Cancer

The elevation of oxidative stress preferentially in cancer cells by efficient NQO1 substrates, which promote ROS generation through redox cycling, has emerged as an effective strategy for cancer therapy, even for treating drug-resistant cancers. Here, we described the identification and structural optimization studies of the hit compound 1, a new chemotype of nonquinone substrate for NQO1 as an efficient ROS generator. Further structure–activity relationship studies resulted in the most active compound 20k, a tricyclic 2,3-dicyano indenopyrazinone, which selectively inhibited the proliferation of NQO1-overexpressing A549 and A549/Taxol cancer cells. Furthermore, 20k dramatically elevated the intracellular ROS levels through NQO1-catalyzed redox cycling and induced PARP-1-mediated cell apoptosis in A549/Taxol cells. In addition, 20k significantly suppressed the growth of A549/Taxol xenograft tumors in mice with no apparent toxicity observed in vivo. Together, 20k acts as an efficient NQO1 substrate and may be a new option for the treatment of NQO1-overexpresssing drug-resistant NSCLC