Myoferlin is a multiple C2-domain-containing protein that regulates membrane repair, tyrosine kinase receptor function and endocytosis in myoblasts and endothelial cells. Recently it has been reported as overexpressed in several cancers and shown to contribute to proliferation, migration and invasion of cancer cells. We have previously demonstrated that myoferlin regulates epidermal growth factor receptor activity in breast cancer. In the current study, we report a consistent overexpression of myoferlin in triple-negative breast cancer cells (TNBC) over cells originating from other breast cancer subtypes. Using a combination of proteomics, metabolomics and electron microscopy, we demonstrate that myoferlin depletion results in marked alteration of endosomal system and metabolism. Mechanistically, myoferlin depletion caused impaired vesicle traffic that led to a misbalance of saturated/unsaturated fatty acids. This provoked mitochondrial dysfunction in TNBC cells. As a consequence of the major metabolic stress, TNBC cells rapidly triggered AMP activated protein kinase-mediated metabolic reprogramming to glycolysis. This reduced their ability to balance between oxidative phosphorylation and glycolysis, rendering TNBC cells metabolically inflexible, and more sensitive to metabolic drug targeting in vitro. In line with this, our in vivo findings demonstrated a significantly reduced capacity of myoferlin-deficient TNBC cells to metastasise to lungs. The significance of this observation was further supported by clinical data, showing that TNBC patients whose tumors overexpress myoferlin have worst distant metastasis-free and overall survivals. This novel insight into myoferlin function establishes an important link between vesicle traffic, cancer metabolism and progression, offering new diagnostic and therapeutic concepts to develop treatments for TNBC patients.

SummaryWe investigated the effect of propofol on endothelial cells subjected to the peroxynitrite (ONOO 2 ) donor 3-morpholino sydnonimine (SIN-1). Cells were incubated overnight with 0.5, 1.0 or 2.0 mm SIN-1, with or without 10 23 m propofol (Diprivanw). Cytotoxicity, assessed by measuring the release of pre-incorporated 51 Cr, increased when the concentration of SIN-1 increased, and was significantly decreased by 10 23 m propofol (90%, 78% and 28% of protection against 0.5, 1.0 and 2.0 mm SIN-1, respectively). Cell protection against 1 mm SIN-1 was tested with 0.03±1.0 mm propofol and this was compared to tyrosine, a target molecule for peroxynitrite. Propofol protected cells in a dose-dependent manner (r 0.98; p , 0.001) and was as effective as tyrosine. Finally, using high-performance liquid chromatography, we demonstrated that propofol reacted with ONOO 2 more rapidly than did tyrosine, inhibiting nitrotyrosine formation. In the absence of propofol, 3.5 mm ONOO 2 with 1 mm tyrosine yielded 39.6% nitrotyrosine, but nitrotyrosine was not produced when 5 mm propofol was added. We conclude that propofol protects endothelial cells against the toxicity of ONOO 2 . The anti-oxidant properties of propofol can be partially attributed to its scavenging effect on peroxynitrite, a property that might be relevant in pathological situations involving a significant contribution of peroxynitrite to tissue damage.

The NSAIDs possess variable degrees of antioxidant activities, linked to their ability to react with HOCl, lipid peroxides or ONOO-. These antioxidant activities could offer interesting targeted side-effects in the treatment of joint inflammatory diseases.

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