Glioblastoma | EPFL Graph Search

Glioblastoma, previously known as glioblastoma multiforme (GBM), is the most aggressive and most common type of cancer that originates in the brain, and has very poor prognosis for survival. Initial signs and symptoms of glioblastoma are nonspecific. They may include headaches, personality changes, nausea, and symptoms similar to those of a stroke. Symptoms often worsen rapidly and may progress to unconsciousness. The cause of most cases of glioblastoma is not known. Uncommon risk factors include genetic disorders, such as neurofibromatosis and Li–Fraumeni syndrome, and previous radiation therapy. Glioblastomas represent 15% of all brain tumors. They are thought to arise from astrocytes. The diagnosis typically is made by a combination of a CT scan, MRI scan, and tissue biopsy. There is no known method of preventing the cancer.

Combinatorial targeting of angiogenesis with inducers of autophagy in the treatment of glioblastoma multiforme

Julie Laetitia Scotton

Malignant gliomas represent 80% of tumors developing in the central nervous system, with 50% being glioblastomas (GBM), the most aggressive form of the disease. The benefit from current therapies is very limited, the overall 5-year survival rate of patients with GBM being less than 5%. Thus, there is an urgent need for better therapies. It has been reported that the use of tricyclic antidepressants (TCAs) is linked with reduced incidence of gliomas. In line with these observations, our lab previously demonstrated that combining imipramine (IM), a TCA that activates adenylate cyclase and elevates production of cAMP, with ticlopidine (TIC), an inhibitor of the purinergic receptor P2Y12 that otherwise suppresses cAMP, results in a concerted increase in the levels of intracellular cAMP, which consequently stimulates increased autophagy in glioma cells, leading to autophagy-associated cell death (AACD) in culture and during orthotopic tumor growth. In several mouse models of glioma, the combination improved survival and reduced malignant grade. Seeking to assess the therapeutic translational potential of these repurposed drugs, particularly IM, we performed pre-clinical trials combining IM+/-TIC with anti-VEGF therapy, which is commonly used in patients with GBM; such anti-angiogenic therapy is associated with a transitory improvement in progression-free survival and quality of life, but does not translate into an overall survival benefit. Using genetic mouse models with enabling bioluminescent monitoring of the cancer cells, we treated established GBMs with imipramine, ticlopidine, and B20S, an anti-mouse VEGF monoclonal antibody. We observed transient stabilization of tumor growth, and the overall survival was significantly extended in the regimens combining B20S with IM +/- TIC compared to control and single treatments. Similar to clinical observations in GBM patients treated with anti-angiogenic therapy, mice treated with B20S alone had no survival benefit, implicating a synergetic effect for the combination of anti-VEGF treatment with imipramine and ticlopidine. We found that the combinatorial therapy elicited further increases in autophagy and displayed some indication of blood vessel normalization, concomitant with an elevation of CD8+T lymphocyte infiltration into the orthotopic tumors. Notably, we could partially reverse the beneficial effect of the combinations using a CD8+T cell-depleting antibody, revealing the involvement of the recruited CD8+T cells in the efficacy of the combinatorial treatment, in addition to the cell-intrinsic autophagy-associated death that is demonstrable in culture and in tumors. Together, these results suggest a strategy to improve anti-angiogenic therapy in patients with glioblastoma, by using repurposed FDA-approved drugs that markedly elevate autophagy in concert with anti-VEGF therapy. The recruitment of CD8+ T cells into the treated tumors and their evident contribution to therapeutic efficacy motivates ongoing experiments aimed to heighten and sustain the induced anti-tumor immune response.

EPFL2018

Conversion of mouse neural stem cells into glioma cancer stem cells

Caroline Turk

Gliomas are the most common and lethal primary adult human brain cancers. The most lethal form of glioma is glioblastoma multiforme (GBM). Multiple apparently differentiated cell types are present within these tumours, including varying proportions of astrocytes and oligodendrocytes. The identification of new GBM subtypes, the role of the cell-of-origin and the role of commonly disrupted genes are active areas of investigation. Of particular interest to this laboratory is the recent realisation that GBMs may be driven by and initiated from tumorigenic stem cells. Our goal was to develop a mouse model of the disease based on genetic manipulation of in vitro neural stem (NS) cell lines. Importantly, this would enable us to define the contribution of each oncogenic pathway in altering the self-renewal of these cells. The original hypothesis was that the simultaneous activation of three critical pathways (RTK/PI3K, Rb and p53) would be required to confer a glioma-like phenotype. However, surprisingly we found that forced expression of the commonly amplified cyclin dependent kinase-4 (CDK4) was sufficient to elicit reduced dependency on growth factor signalling and a decreased sensitivity to the differentiation factor BMP4. Moreover, preliminary results indicate that the mRNA expression of the proto-oncogene Akt2 increases in CDK4 transfectants, suggestive of a feedback mechanism. We tested whether constitutive expression of Akt2 together with CDK4 increases the severity of the phenotype and initial results suggest this is the case. These findings provide encouragement that minimal genetic events will be required in order to transform NS cells in vitro. These cells can now be tested for in vivo tumorigenicity following transplantation. Finally, we have also generated CDK4 overexpressing cell lines in a specific NS cell variant which I identified as expressing an oligodendrocyte differentiation bias (MG1-7). We are therefore now in a position to assess whether differentiation behaviour is affected by the disruption of this pathway. Together these findings highlight the utility of mouse NS cells as a tool to study glioma

2009

Development of new anticancer agents based on [alpha]-mannosidase inhibition

Hélène Fiaux

Enzymes that are involved in the synthesis and processing of oligosaccharides, such as glycosidases, are important catalysts for the specific assembly of oligosaccharide structures on proteins. Design and preparation of selective inhibitors of these enzymes are of high interest as these molecules can be used to modulate cellular functions. Moreover, they may provide potential drugs in new therapeutic strategies. In particular, swainsonine (Swa), a natural inhibitor of Golgi α-mannosidase II, reduces certain tumors and hematological dysfunctions. Nevertheless, some side effects resulted in limitations for the development of this compound in medicinal treatments. Recently, our laboratory has developed a new combinatorial methodology for the disclosure of glycosidase inhibitors based on the dihydroxypyrrolidine scaffold found in Swa. This method allowed the preparation of a new family of selective and competitive a-mannosidase inhibitors with inhibitory activities (Ki values) ranging from 3 µM to 135 nM for the best congeners toward α-mannosidase from jack bean, a reliable model enzyme for mammalian Golgi α-mannosidase II. The aim of the present work was to design and synthesise optimized inhibitors of α-mannosidases II based on a 2-aminomethyl-3,4-dihydroxypyrrolidine scaffold and to assess their potential as new anti cancer leads. In a first time, a structural study was carried out through the analysis of x-ray structures of the best inhibitors previously developed in our laboratory complexed to Golgi α-mannosidase II from Drosophila melanogaster (dGMII), which presents a high sequence identity with the human enzyme. The binding mode of these inhibitors could be thus established. This study combined with docking experiments allowed us to design inhibitors of α-mannosidase II, with improved efficacy. The best congener (3R,4R,5R)-3,4-dihydroxy-5-({[(1R)-2-hydroxy-1-phenylethyl]amino}methyl)-1-methylpyrrolidin-2-one displayed an enhanced inhibitory potency against dGMII (IC50 = 0.5 µM vs 80 µM for the first generation inhibitor). Introduction of a polar substituent on the C(5) position of the pyrrolidine ring accounted for this improved activity as revealed by the x-ray structure of this new derivative complexed to dGMII which displayed additional interactions with active site residues. In a second time, these new α-mannosidase inhibitors have been evaluated as anti cancer agents and their effects were determined on human cancer cells from glioblastoma and melanoma, two tumors associated with a high proliferative and invasive potential, multiple resistance toward conventional chemotherapeutic agents, and poor prognosis. As these compounds were not able to inhibit cellular growth, probably due to a poor cellular uptake, derivatization of our inhibitors into more lipophilic esters, ethers and amides derivatives was envisaged. In particular, introduction of a 4-bromobenzoate moiety resulted in an improvement of cellular uptake, leading to a complete inhibition of cellular growth at 300 µM with inhibitors (2R)-2-({[(2R,3R,4S)-3,4-dihydroxypyrrolidin-2-yl]methyl}amino)-2-phenylethyl 4-bromobenzoate and (2R)-2-({[(2R,3R,4R)-3,4-dihydroxy-1-methyl-5-oxopyrrolidin-2-yl]methyl}amino)-2-phenylethyl 4-bromobenzoate. Under the same conditions, Swa didn't provide any significant growth inhibition. Moreover, exposure of human fibroblasts, as model of healthy cells, to our lead derivatives revealed some selectivity toward tumoral cells. It was hypothesized that cellular esterases were able to hydrolyse the ester moiety and thus release the more hydrophilic parent inhibitors within the tumoral cells. Finally, in order to get more insights into the mode of action of our derivatives, their inhibitory activity on α-mannosidases from human glioblastoma extracts was determined and compared to the activity of Swa. The first generation inhibitor presented a moderate inhibitory potency on α-mannosidases whereas the optimized derivative displayed potent inhibitory activity on human α-mannosidases (IC50 = 50 µM decreased to 0.5 µM). Nevertheless, Swa presented higher potency than our new lead (IC50 = 10-50 nM). It was also determined by gel filtration that the cellular α-mannosidases targeted by our pyrrolidine based inhibitors displayed apparent molecular weight of about 120 kD.

EPFL2007