Histological and molecular analysis of brain metastases

CERVOXYInternational audienc

Fibronectin expression in glioblastomas promotes cell cohesion, collective invasion of basement membrane in vitro and orthotopic tumor growth in mice.

International audience: Glioblastoma multiforme (GBM) are highly invasive and angiogenic malignancies with a median survival time from diagnosis of <15 months. Previous work has revealed robust overexpression of fibronectin (FN) mRNA in GBM, although immunohistochemical staining of FN in these tumors is typically associated with the angiogenic vasculature. Here we sought to examine the expression of tumor cell FN and address its possible involvement in the invasive phenotype of GBM. We found that FN was expressed and assembled into fibrillar arrays in human tumors and in established GBM lines. Cultured cells spontaneously formed dense cellular networks and spheroid-like domes. Depletion of FN by targeted-short hairpin RNA expression disrupted matrix assembly and multicellular network organization by exerting profound effects on cell adhesion and motility. Although FN depletion enhanced persistent directional migration of single cells, it compromised collective invasion of spheroids through a laminin-rich matrix and sensitized cells to ionizing radiation. In orthotopic grafts, FN depletion significantly reduced tumor growth and angiogenesis. Together our results show that FN produced by the tumor cells has a role in GBM pathophysiology and they provide insights into the implications that targeting FN interactions may have for combating this dreaded disease.Oncogene advance online publication, 5 August 2013; doi:10.1038/onc.2013.305

Urinary ketone body loss leads to degeneration of brain white matter in elderly SLC5A8-deficient mice.

SLC5A8 is a sodium-coupled monocarboxylate and ketone transporter expressed in various epithelial cells. A putative role of SLC5A8 in neuroenergetics has been also hypothesized. To clarify this issue, we studied the cerebral phenotype of SLC5A8-deficient mice during aging. Elderly SLC5A8-deficient mice presented diffuse leukoencephalopathy characterized by intramyelinic oedema without demyelination suggesting chronic energetic crisis. Hypo-metabolism in the white matter of elderly SLC5A8-deficient mice was found using &lt;sup&gt;99m&lt;/sup&gt; Tc-hexamethylpropyleneamine oxime (HMPAO) single-photon emission CT (SPECT). Since the SLC5A8 protein could not be detected in the mouse brain, it was hypothesized that the leukoencephalopathy of aging SLC5A8-deficient mice was caused by the absence of slc5a8 expression in a peripheral organ, i.e. the kidney, where SLC5A8 is strongly expressed. A hyper-excretion of the ketone β-hydroxybutyrate (BHB) in the urine of SLC5A8-deficient mice was observed and showed that SLC5A8-deficient mice suffered a cerebral BHB insufficiency. Elderly SLC5A8-deficient mice also presented altered glucose metabolism. We propose that the continuous renal loss of BHB leads to a chronic energetic deficiency in the brain of elderly SLC5A8-deficient mice who are unable to counterbalance their glucose deficit. This study highlights the importance of alternative energetic substrates in neuroenergetics especially under conditions of restricted glucose availability

Autophagy inactivation in osteosarcoma leads to the appearance of poor prognosis-associated factors

Osteosarcoma (OS) is a bone cancer exhibiting a 20% survival rate for metastatic patients, which motivates the development of new therapeutic options. Among the various new treatment approaches, modulation of autophagy is the subject of rising interest. In addition to its pro-survival role in established tumors, autophagy recently emerged as an active player in the crosstalk between tumor and stromal cells. In OS, although the knockdown of key autophagy genes in human cell lines demonstrates a protumoral role of autophagy, the analysis of patient tumors indicates that lack of LC3-positive punctae at resection following neoadjuvant chemotherapy is a poor prognostic marker, suggesting that loss of autophagy is not detrimental for the tumor. In the present work, we analyzed the consequences of autophagy inactivation in OS cells both on tumor development and on bone microenvironment in an orthotopic syngeneic model. We found that inactivation of the autophagy-essential gene Atg5 in OS cells decreases their tumorigenic properties in vitro. However, these effects were no longer observed in vivo, likely due to microenvironment modifications such as overexpression of the major OS-promoting factor TGF-β or increased infiltration of Foxp3-positive and CD31-positive cells in Atg5 KO tumors. In addition, autophagy-deficient tumor cells stimulate the in vitro formation of osteoclast, the cells in charge of bone resorption which can release bone matrix-embedded growth factors thereby stimulating tumor growth. Taken together, these results suggest that Atg5 inactivation in OS cells is associated with microenvironment modifications known as poor prognosis-associated factors in OS, and could thus balance the negative cell-autonomous effects of autophagy suppression. Abbreviations: ACTB -β-actin; Atg -autophagy-related; Baf-A1 - Bafilomycin-A1; CSC -cancer stem cells; Col1A -type 1a collagen; d -day; HBSS -Hank’s balanced salt solution; LC3 -microtubule-associated protein 1 light chain 3 protein; SQSTM1/p62 -sequestosome; OB -osteoblast; OC -osteoclast; OS -osteosarcoma; TEM -transmission electron microscopy; TGF-β -transforming growth factor β; TRAP -acid phosphatase 5, tartrate-resistant

A driver role for GABA metabolism in controlling stem and proliferative cell state through GHB production in glioma

Cell populations with differing proliferative, stem-like and tumorigenic states co-exist in most tumors and especially malignant gliomas. Whether metabolic variations can drive this heterogeneity by controlling dynamic changes in cell states is unknown. Metabolite profiling of human adult glioblastoma stem-like cells upon loss of their tumorigenicity revealed a switch in the catabolism of the GABA neurotransmitter toward enhanced production and secretion of its by-product GHB (4-hydroxybutyrate). This switch was driven by succinic semialdehyde dehydrogenase (SSADH) downregulation. Enhancing GHB levels via SSADH downregulation or GHB supplementation triggered cell conversion into a less aggressive phenotypic state. GHB affected adult glioblastoma cells with varying molecular profiles, along with cells from pediatric pontine gliomas. In all cell types, GHB acted by inhibiting α-ketoglutarate-dependent Ten–eleven Translocations (TET) activity, resulting in decreased levels of the 5-hydroxymethylcytosine epigenetic mark. In patients, low SSADH expression was correlated with high GHB/α-ketoglutarate ratios, and distinguished weakly proliferative/differentiated glioblastoma territories from proliferative/non-differentiated territories. Our findings support an active participation of metabolic variations in the genesis of tumor heterogeneity. © 2016, The Author(s)