Abstract
Metabolic dysregulation is an important hallmark of cancer. Nicotinamide (NAM), a water-soluble amide form of niacin (vitamin B3), is currently available as a supplement for maintaining general physiologic functions. NAM is a crucial regulator of mitochondrial metabolism and redox reactions. In this study, we aimed to identify the mechanistic link between NAM-induced metabolic regulation and the therapeutic efficacy of NAM in triple-negative breast cancer (TNBC). The combined analysis using multiomics systems biology showed that NAM decreased mitochondrial membrane potential and ATP production, but increased the activities of reverse electron transport (RET), fatty acid β-oxidation and glycerophospholipid/sphingolipid metabolic pathways in TNBC, collectively leading to an increase in the levels of reactive oxygen species (ROS). The increased ROS levels triggered apoptosis and suppressed tumour growth and metastasis of TNBC in both human organoids and xenograft mouse models. Our results showed that NAM treatment leads to cancer cell death in TNBC via mitochondrial dysfunction and activation of ROS by bifurcating metabolic pathways (RET and lipid metabolism); this provides insights into the repositioning of NAM supplement as a next-generation anti-metabolic agent for TNBC treatment.
Discussion
In the present study, we treated each mouse with 1000 or 2000 mg·kg−1 NAM, and no side effects were observed. In a randomized clinical trial, 1000–2000 mg of NAM per day as a supplement showed potential benefits for improving cardiovascular and other physiological functions with limited side effects [56]. The doses used for treating animals are compatible with 80 or 160 mg·kg−1 for humans, which are two to three times higher than those reported previously [56].
