antibody or with human or bovine holotransferrin showed that it activated ERK1/ERK2 and p38 MAP kinases. Integrity of lipid rafts was required for MAPK activation. Co-localization of TfR2 with CD81, a raft tetraspanin exported through exosomes, prompted us to investigate exosomes released by HepG2 and K562 cells into culture medium. TfR2, CD81 and to a lesser extent caveolin-1, were found to be part of the exosomal budding vesicles. In conclusion, the present study indicates that TfR2 localizes in LDTI microdomains, where it promotes cell signalling, and is exported out of the cells through the exosome pathway, where it acts as an intercellular messenger.Key words: Transferrin, Iron metabolism, Lipid rafts, Cell signalling SummaryTfR2 localizes in lipid raft domains and is released in exosomes to activate signal transduction along the MAPK pathway

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Under physiological conditions, transferrin receptor 2 (TfR2) is expressed in the liver and its balance is related to the cell cycle rather than to intracellular iron levels. We recently showed that TfR2 is highly expressed in glioblastoma cell lines. Here, we demonstrate that, in these cells, TfR2 appears to localize in lipid rafts, induces extracellular signal-regulated kinase 1/2 phosphorylation after transferrin binding, and contributes to cell proliferation, as shown by RNA silencing experiments. In vitro hypoxic conditions induce a significant TfR2 up-regulation, suggesting a role in tumor angiogenesis. As assessed by immunohistochemistry, the level of TfR2 expression in astrocytic tumors is related to histologic grade, with the highest expression observed in glioblastomas. The level of TfR2 expression represents a favorable prognostic factor, which is associated with the higher sensitivity to temozolomide of TfR2-positive tumor cells in vitro. The endothelial cells of glioblastoma vasculature also stain for TfR2, whereas those of the normal brain vessels do not. Importantly, TfR2 is expressed by the subpopulation of glioblastoma cells with properties of cancer-initiating cells. TfR2-positive glioblastoma cells retain their TfR2 expression on xenografting in immunodeficient mice. In conclusion, our observations demonstrate that TfR2 is a neoantigen for astrocytomas that seems attractive for developing target therapies.

BackgroundMany biomedical publications refer to data obtained from collections of biosamples. Sharing such bioresources (biological samples, data, and databases) is paramount for the present governance of research. Recognition of the effort involved in generating, maintaining, and sharing high quality bioresources is poorly organized, which does not encourage sharing. At publication level, the recognition of such resources is often neglected and/or highly heterogeneous. This is a true handicap for the traceability of bioresource use. The aim of this article is to propose, for the first time, a guideline for reporting bioresource use in research articles, named CoBRA: Citation of BioResources in journal Articles.MethodsAs standards for citing bioresources are still lacking, the members of the journal editors subgroup of the Bioresource Research Impact Factor (BRIF) initiative developed a standardized and appropriate citation scheme for such resources by informing stakeholders about the subject and raising awareness among scientists and in science editors’ networks, mapping this topic among other relevant initiatives, promoting actions addressed to stakeholders, launching surveys, and organizing focused workshops.ResultsThe European Association of Science Editors has adopted BRIF’s suggestion to incorporate statements on biobanks in the Methods section of their guidelines. The BRIF subgroup agreed upon a proposed citation system: each individual bioresource that is used to perform a study and that is mentioned in the Methods section should be cited as an individual “reference [BIORESOURCE]” according to a delineated format. The EQUATOR (Enhancing the QUAlity and Transparency Of health Research) network mentioned the proposed reporting guideline in their “guidelines under development” section.ConclusionsEvaluating bioresources’ use and impact requires that publications accurately cite such resources. Adopting the standard citation scheme described here will improve the quality of bioresource reporting and will allow their traceability in scientific publications, thus increasing the recognition of bioresources’ value and relevance to research.Please see related article: http://dx.doi.org/10.1186/s12916-015-0284-9.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been reported to exhibit therapeutic activity in cancer. However, many tumors remain resistant to treatment with TRAIL. Therefore, small molecules that potentiate the cytotoxic effects of TRAIL could be used for combinatorial therapy. Here we found that the ionophore antibiotic salinomycin acts in synergism with TRAIL, enhancing TRAIL-induced apoptosis in glioma cells. Treatment with low doses of salinomycin in combination with TRAIL augmented the activation of caspase-3 and increased TRAIL-R2 cell surface expression. TRAIL-R2 upmodulation was required for mediating the stimulatory effect of salinomycin on TRAIL-mediated apoptosis, since it was abrogated by siRNA-mediated TRAIL-R2 knockdown. Salinomycin in synergism with TRAIL exerts a marked anti-tumor effect in nude mice xenografted with human glioblastoma cells. Our results suggest that the combination of TRAIL and salinomycin may be a useful tool to overcome TRAIL resistance in glioma cells and may represent a potential drug for treatment of these tumors. Importantly, salinomycin+TRAIL were able to induce cell death of well-defined glioblastoma stem-like lines.