While the prevalence of breast cancer metastasis in the brain is significantly higher in triple negative breast cancers (TNBCs), there is a lack of novel and/or improved therapies for these patients. Monoacylglycerol lipase (MAGL) is a hydrolase involved in lipid metabolism that catalyzes the degradation of 2-arachidonoylglycerol (2-AG) linked to generation of pro- and anti-inflammatory molecules. Here, we targeted MAGL in TNBCs, using a potent carbamate-based inhibitor AM9928 (hMAGL IC(50) = 9 nM) with prolonged pharmacodynamic effects (46 h of target residence time). AM9928 blocked TNBC cell adhesion and transmigration across human brain microvascular endothelial cells (HBMECs) in 3D co-cultures. In addition, AM9928 inhibited the secretion of IL-6, IL-8, and VEGF-A from TNBC cells. TNBC-derived exosomes activated HBMECs resulting in secretion of elevated levels of IL-8 and VEGF, which were inhibited by AM9928. Using in vivo studies of syngeneic GFP-4T1-BrM5 mammary tumor cells, AM9928 inhibited tumor growth in the mammary fat pads and attenuated blood brain barrier (BBB) permeability changes, resulting in reduced TNBC colonization in brain. Together, these results support the potential clinical application of MAGL inhibitors as novel treatments for TNBC.
