Triple negative breast cancer (TNBC) is aggressive with a worse prognosis. We have recently shown that bitter melon extract (BME) treatment was more effective in inhibition of TNBC tumor growth in mouse models as compared to ER positive breast tumor growth. Aberrant dysregulation of lipid metabolism is associated with breast cancer progression, however, anti-cancer mechanism of BME linking lipid metabolism in breast cancer growth remains unexplored. Here, we observed that accumulation of esterified cholesterol was reduced in BME treated TNBC cell lines as compared to control cells. We next evaluated expression levels of acyl-CoA: cholesterol acyltransferase 1 (ACAT-1) in TNBC cells treated with BME. Our results demonstrated that BME treatment inhibited ACAT-1 expression in TNBC cells. Subsequently, we found that sterol regulatory element-binding proteins-1 and -2, and FASN was significantly reduced in BME treated TNBC cell lines. Low-density lipoprotein receptor was also downregulated in BME treated TNBC cells as compared to control cells. We further demonstrated that BME feeding reduced tumor growth in TNBC mammospheres implanted into NSG mice, and inhibits ACAT-1 expression. To our knowledge, this is the first report demonstrating BME suppresses TNBC cell growth through ACAT-1 inhibition, and have potential for additional therapeutic regimen against human breast cancer.

The mechanisms underlying sterol transport in mammalian cells are poorly understood. In particular, how cholesterol internalized from HDL is made available to the cell for storage or modification is unknown. Here, we describe three ER-resident proteins (Aster-A, -B, -C) that bind cholesterol and facilitate its removal from the plasma membrane. The crystal structure of the central domain of Aster-A broadly resembles the sterol-binding fold of mammalian StARD proteins, but sequence differences in the Aster pocket result in a distinct mode of ligand binding. The Aster N-terminal GRAM domain binds phosphatidylserine and mediates Aster recruitment to plasma membrane-ER contact sites in response to cholesterol accumulation in the plasma membrane. Mice lacking Aster-B are deficient in adrenal cholesterol ester storage and steroidogenesis because of an inability to transport cholesterol from SR-BI to the ER. These findings identify a nonvesicular pathway for plasma membrane to ER sterol trafficking in mammals.

Regulatory T (Treg) cells induce an immunosuppressive microenvironment that is a major obstacle for successful tumor immunotherapy. Dissecting the regulatory mechanisms between energy metabolism and functionality in Treg cells will provide insight toward developing novel immunotherapies against cancer. Here we report that human naturally occurring and tumor-associated Treg cells exhibit distinct metabolic profiles with selectivity for glucose metabolism compared with effector T cells. Treg-mediated accelerated glucose consumption induces cellular senescence and suppression of responder T cells through cross-talk. TLR8 signaling selectively inhibits glucose uptake and glycolysis in human Treg cells, resulting in reversal of Treg suppression. Importantly, TLR8 signaling-mediated reprogramming of glucose metabolism and function in human Treg cells can enhance anti-tumor immunity in vivo in a melanoma adoptive transfer T cell therapy model. Our studies identify mechanistic links between innate signaling and metabolic regulation of human Treg suppression, which may be used as a strategy to advance tumor immunotherapy.

Halogens are widely used highly toxic chemicals that pose potential threat to humans due to their abundance. Halogens such bromine (Br) cause severe pulmonary and systemic injuries however, the mechanisms of their toxicity are largely unknown. Here we demonstrate that Br and reactive brominated species produced in the lung and released in blood, reach the heart and cause acute cardiac ultrastructural damage and dysfunction in rats. Br-induced cardiac damage was demonstrated by acute (3-24h) increases in circulating troponin I, hFABP and NT-proBNP. Transmission electron microscopy demonstrated acute (3-24h) cardiac contraction band necrosis, disruption of z-discs, and mitochondrial swelling and disorganization.Echocardiography and hemodynamic analysis revealed left ventricular (LV) systolic and diastolic dysfunction at 7 days. Plasma and the LV tissue had increased levels of brominated fatty acids. 2-bromohexadecanal (Br-HDA) injected into the LV cavity of a normal rat caused acute LV enlargement with extensive disruption of the sarcomeric architecture and mitochondrial damage. There was extensive infiltration of neutrophils and increased myeloperoxidase levels in the hearts of Br or Br reactant exposed rats. Increased bromination of SERCA and increased phosphalamban after Br inhalation decreased cardiac SERCA activity by 70%. SERCA inactivation was accompanied by increased calcium sensitive LV calpain activity. A calpain specific inhibitor MDL28170 administered within 1h after exposure significantly decreased calpain activity and acute mortality. Bromine inhalation and formation of reactive brominated species caused acute cardiac injury and myocardial damage that can lead to heart failure.