RIDR-PI-103 was synthesized as described [29 (link)]. PI-103 (Cat# S1038) was obtained from Selleckchem (Houston, Texas, USA). All drugs were dissolved in dimethyl sulfoxide (DMSO) (Fisher Scientific, Waltham, Massachusetts, USA) at desired concentrations and stored at −20°C. Glutathione was obtained from Fisher Scientific (Cat# BP25211). N-acetyl cysteine (NAC) was obtained from Fisher Scientific (Cat# AAA1540936). TBHP was obtained from Fisher Scientific (Cat# AC180340050). Dabrafenib (Cat# D-5699) and trametinib (Cat# T-8123) were purchased from LC Laboratories (Woburn, Massachusetts, USA).