The rheumatoid arthritis drug Auranofin targets peroxiredoxin 1 and peroxiredoxin 2 to trigger ROS-endoplasmic reticulum stress axis-mediated cell death and cytoprotective autophagy.

Auranofin (AF) is a gold-based compound and it has been used in the treatment of rheumatoid arthritis for over four decades. Recently, it has been demonstrated to show significant antitumor activity across various cancer types and is being repurposed as an anticancer drug. However, the precise mechanisms underlying its antitumor effects, particularly its binding targets, remain poorly understood. Here, we demonstrate that Auranofin (AF) exerts cytotoxic effects in 786-O renal cancer cells via inducing apoptosis. Mechanistic studies reveal that AF induces reactive oxygen species (ROS) accumulation, which is a key factor in mediating AF-induced stress and subsequently apoptosis. Notably, both ROS and ER stress induce autophagy, and inhibition of autophagy further enhances AF-induced cytotoxicity. Interestingly, activity-based protein profiling (ABPP) analysis identifies two key antioxidant enzymes, peroxiredoxin 1 (PRDX1) and peroxiredoxin 2 (PRDX2), as direct binding targets of AF. Importantly, overexpression of PRDX1 or PRDX2 inhibits AF-induced ROS accumulation and subsequent apoptosis. Overall, our findings demonstrate that AF induces apoptosis by covalently binding to PRDX1/2 to inhibit its activity, leading to ROS accumulation, which triggers ER stress and apoptosis. At the same time, ER stress triggers a cytoprotective autophagic response. These findings provide novel insights into the mechanism of AF-induced cytotoxicity and suggest PRDX1/2 as critical targets for the development of anti-renal cancer therapies.