Tuberous sclerosis complex (TSC) is a genetic multi-organ disorder characterized by the development of neoplastic lesions in kidney, lung, brain, heart and skin. It is caused by an inactivating mutation in tumor suppressor genes coding the TSC1/TSC2 complex, resulting in hyperactivation of mTOR- and Raf/MEK/MAPK-dependent signaling that stimulates tumor cell proliferation and metastasis. Despite its oncogenic effect, cells with TSC deficiency were more sensitive to oxidative stress and dependent on mitochondrial metabolism, providing a rationale for a new therapeutic approach. The presented study shows that simultaneous inhibition of two major pathways regulating redox homeostasis using L-Buthionine-sulfoximine (BSO, glutathione synthesis inhibitor) and auranofin (thioredoxin reductase inhibitor) induces oxidative burst, mitochondrial damage and necrotic cell death in TSC2 deficient cells in a highly synergistic and cell context-specific manner. Furthermore, blocking RIP1/RIP3-dependent signaling using chemical inhibitors necrostatin-1 and necrosulfonamide (NSA), reported by others to protect from some cytotoxic stimuli, synergizes with BSO and auranofin in killing TSC2 deficient cells. Expression analysis demonstrated that RIP1 and RIP3 protein levels are elevated in cells with TSC2 deficiency, and their inactivation enhances mitochondrial dysfunction. Finally, supplementation with the mitochondrial metabolite alpha-ketoglutarate, whose synthesis is regulated by RIP1/RIP3, rescues cells from the sensitizing effect of necrostatin-1 and NSA. Together, this study identifies a novel TSC context-dependent role of RIP1/RIP3 signaling in regulating mitochondrial and oxidative homeostasis, and substantiates glutathione, thioredoxin and RIP1/RIP3 pathways targeting as a promising therapeutic approach against TSC-associated tumors.

Citation Format: Piotr T. Filipczak, Cindy Thomas, Wenshu Chen, Andrew Salzman, Jacob D. McDonald, Yong Lin, Steven A. Belinsky. TSC deficiency unmasks a novel protective role of RIP1/RIP3 signaling against mitochondrial and oxidative stress-induced cell death. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3731.