Development of novel nitric oxide-releasing quinolinedione/furoxan hybrids as NQO1 inhibitors for intervention of drug-resistant hepatocellular cancer

A series of novel nitric oxide (NO)-releasing 5,8-quinolinedione/furoxan hybrids (8a-h and 9a-h) were designed and synthesized through coupling different alkanolamine substituted phenylsulfonyl furoxan with 5,8-quinolinedione. Most compounds displayed high cytotoxic activity against drug-sensitive/-resistant cancer cells. In particular, the IC50 of 9a (0.42 µM) was about 9-fold lower than that of β-lap (3.69 µM) and 12-fold lower than that of SAHA (5.24 µM) in drug-resistant cancer cells. Also, 9a was demonstrated to selectively inhibit the growth of Bel7402/5-FU cancer cells. Mechanistic studies demonstrated that 9a could serve as an NO donor and nicotinamide quinone oxidoreductase 1 (NQO1) inhibitor (IC50 = 0.8 µM), which could induce the highest level of NO and reactive oxygen species (ROS) in Bel-7402/5-FU cancer cells. Furthermore, 9a could promote tumor cell apoptosis and autophagy via regulation of apoptosis-related protein (Bax, Bcl-2, and Caspase 3) and autophagy-associated proteins (LC3 and p62) in Bel-7402/5-FU cells. Taken together, 9a may be considered as a promising candidate for a further comprehensive study involving drug-resistant hepatocellular carcinoma.