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World Health Organization classifies gliomas according to their cellular features and their grade of malignancy (from I to IV) (4). Glioblastoma multiforme (GBM), 3 also referred to as grade IV astrocytoma, is the most frequent class of malignant primary brain tumor and one of the most aggressive forms of cancer. There is a poor prognosis for patients with GBM, the median survival being 9 -12 months, and this does not significantly improve even after aggressive treatment with multiple approaches, including surgery, chemotherapy, and radiotherapy (5). This poor survival rate seems to be mainly due to the marked invasiveness and proliferation of GBM, as well as to their apoptotic resistance and aberrant angiogenesis. These malignancy features could be related to the varying mutations frequently found in GBM tumors that impact different key pathways involved in the control of cell proliferation, survival, differentiation, migration, and DNA repair (6 -9).Among the disregulated signaling pathways in GBMs, PI3K-Akt-PTEN has been identified as being an important oncogenic pathway (10 -12). PI3Ks are members of a unique and conserved family of lipid kinases that phosphorylate the 3Ј-hydroxyl group of phosphatidylinositol and phosphoinositides such as phosphatidylinositol(4,5)P 2 (PIP 2 ), which is converted to phosphatidylinositol(3,4,5)P 3 (PIP 3 ). The activation of PI3Ks can occur through growth factor receptors, G-protein-coupled receptors, cell adhesion molecules, and oncogenes such as Ras. The generated polyphosphoinositides bind to the pleckstrin homology (PH) domain of different proteins, including PDK1 * This work was supported by grants from the University of Milan (to P. G., L. R., and P. V.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. N-[hexanoyl-6-3 H]D-erythro-hexanoyl-sphingosine; HPTLC, high performance thin layer chromatography; NBD-C 6 -Cer, 6-((N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl) sphingosine; FAPP, four phosphate adaptor protein; EGF-FAPP1-PH, PH domain of FAPP1 protein fused with enhanced green fluorescent protein; DN-AKT, dominant negative mutant of Akt; PBS, phosphate-buffered

Glioblastoma is a deadly cancer with intrinsic chemoresistance. Understanding this property will aid in therapy. Glucosylceramide synthase (GCS) is associated with resistance and poor outcome; little is known about glioblastomas. In glioblastoma cells, temozolomide and paclitaxel induce ceramide increase, which in turn promotes cytotoxicity. In drug-resistant cells, both drugs are unable to accumulate ceramide, increased expression and activity of GCS is present, and its inhibitors hinder resistance. Resistant cells exhibit cross-resistance, despite differing in marker expression, and cytotoxic mechanism. These findings suggest that GCS protects glioblastoma cells against autophagic and apoptotic death, and contributes to cell survival under chemotherapy.

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Accumulating evidence suggests that glucolipotoxicity, arising from the combined actions of elevated glucose and free fatty acid levels, acts as a key pathogenic component in type II diabetes, contributing to β-cell dysfunction and death. Endoplasmic reticulum (ER) stress is among the molecular pathways and regulators involved in these negative effects, and ceramide accumulation due to glucolipotoxicity can be associated with the induction of ER stress. Increased levels of ceramide in ER may be due to enhanced ceramide biosynthesis and/or decreased ceramide utilization. Here, we studied the effect of glucolipotoxic conditions on ceramide traffic in INS-1 cells in order to gain insights into the molecular mechanism(s) of glucolipotoxicity. We showed that glucolipotoxicity inhibited ceramide utilization for complex sphingolipid biosynthesis, thereby reducing the flow of ceramide from the ER to Golgi. Glucolipotoxicity impaired both vesicular- and CERT-mediated ceramide transport through (1) the decreasing of phospho-Akt levels which in turn possibly inhibits vesicular traffic, and (2) the reducing of the amount of active CERT mainly due to a lower protein levels and increased protein phosphorylation to prevent its localization to the Golgi. In conclusion, our findings provide evidence that glucolipotoxicity-induced ceramide overload in the ER, arising from a defect in ceramide trafficking may be a mechanism that contributes to dysfunction and/or death of β-cells exposed to glucolipotoxicity.