Anti-Cancer Effects of Auranofin in Human Lung Cancer Cells by Increasing Intracellular ROS Levels and Depleting GSH Levels.

Auranofin, as a thioredoxin reductase (TrxR) inhibitor, has promising anti-cancer activity in several cancer types. However, little is known about the inhibitory effect of auranofin on lung cancer cell growth. We, therefore, investigated the antigrowth effects of auranofin in various lung cancer cells with respect to cell death, reactive oxygen species (ROS), and glutathione (GSH) levels. Treatment with 0~5 µM auranofin decreased cell proliferation and induced cell death in Calu-6, A549, SK-LU-1, NCI-H460, and NCI-H1299 lung cancer cells at 24 h. In addition, 0~5 µM auranofin increased ROS levels, including O2•-, and depleted GSH levels in these cells. N-acetyl cysteine (NAC) prevented growth inhibition and mitochondrial membrane potential (MMP, ∆Ψm) loss in 3 and 5 µM auranofin-treated Calu-6 and A549 cells at 24 h, respectively, and decreased ROS levels and GSH depletion in these cells. In contrast, L-buthionine sulfoximine (BSO) enhanced cell death, MMP (∆Ψm) loss, ROS levels, and GSH depletion in auranofin-treated Calu-6 and A549 cells. Treatment with 3 and 5 µM auranofin induced caspase-3 activation and poly (ADP ribose) polymerase (PARP) cleavage in Calu-6 and A549 cells, respectively. Both were prevented by NAC, but enhanced by BSO. Moreover, TrxR activity was reduced in auranofin-treated Calu-6 and A549 cells. That activity was decreased by BSO, but increased by NAC. In conclusion, these findings demonstrate that auranofin-induced cell death is closely related to oxidative stress resulted from increased ROS levels and GSH depletion in lung cancer cells.

Auranofin inhibits the proliferation of lung cancer cells via necrosis and caspase­dependent apoptosis.

Auranofin, an inhibitor of thioredoxin reductase (TrxR), inhibits the growth of a variety of cancer cells. In the present study, various lung cancer cells were used to investigate the molecular basis of anti­cancer effects of auranofin, including cell death via apoptosis or necrosis and cell cycle arrest. Generally, auranofin inhibited the growth of the tested lung cancer cell lines in a dose­dependent manner with an IC50 of 3­4 µM at 24 h. This agent significantly decreased the activity of TrxR in Calu­6 and A549 lung cancer cells. In addition, auranofin (3­5 µM) triggered necrosis in lung cancer cells measured by the release of lactate dehydrogenase (LDH) into culture media. Auranofin increased the percentages of sub­G1 cells in Calu­6 and A549 cells. DNA flow cytometry showed that auranofin induced G2/M phase arrest of Calu­6 cells. This agent also efficiently induced apoptosis, accompanied by loss of mitochondrial membrane potential (MMP; ∆Ψm), increases in cleavage forms of caspase­3 and poly (ADP­ribose) polymerase (PARP), and a high ratio of BAX to Bcl­2 proteins. Furthermore, various caspase inhibitors reduced apoptosis and MMP (∆Ψm) loss in auranofin­treated Calu­6 cells. In particular, the pan­caspase inhibitor, benzyloxycarbonyl­Val­Ala­Asp­fluoromethylketone (Z­VAD), decreased cleavage forms of caspase­3, ­8, and ­9 in these cells. In conclusion, auranofin inhibited the proliferation of lung cancer cells, especially Calu­6 cells, via cell cycle arrest and cell death due to necrosis or caspase­dependent apoptosis.