Oxidative stress potentiates the therapeutic action of a mitochondrial complex I inhibitor in MYC-driven B-cell lymphoma

Abstract

MYC is a key oncogenic driver and an adverse prognostic factor in multiple types of cancer, including diffuse large B-cell lymphoma (DLBCL). Yet, MYC activation also endows cancer cells with a series of metabolic dependencies, which can provide strategic points for targeted pharmacological intervention. We recently reported that targeting the mitochondrial electron transport chain (ETC) complex I with the small molecule inhibitor IACS-010759 selectively killed MYC-overexpressing lymphoid cells. Here, we unravel the mechanistic basis for this synthetic-lethal interaction and exploit it to improve the anti-tumoral effects of ETC inhibition. In a mouse B-cell line, MYC hyperactivation and IACS-010759 treatment added up to induce oxidative stress, with consequent depletion of reduced glutathione and lethal disruption of redox homeostasis. This effect could be enhanced by targeted pharmacological intervention, with either inhibitors of NADPH production through the pentose phosphate pathway, or with ascorbate (vitamin C), known to contribute pro-oxidant effects when administered at high doses. In these conditions, ascorbate synergized with IACS-010759 to kill MYC-overexpressing cells in vitro and reinforced its therapeutic action against human B-cell lymphoma xenografts. Hence, ETC inhibition and high-dose ascorbate might improve the outcome of patients affected by high-grade lymphomas and other MYC-driven cancers. Key point #1MYC and the ETC complex I inhibitor IACS-010759 elicit different reactive oxygen species (ROS) that cooperate to disrupt redox homeostasis. Key point #2Further boosting of oxidative stress with high doses of ascorbate increases the killing of MYC-driven lymphoma xenografts by IACS-010759.