Browsing by Subject "Glioblastoma"

Glioblastoma Multiforme (GBM) is the most common and aggressive types of glioma in adults. Autophagy allows degradation and recycling of cellular components such as damaged proteins and dysfunctional organelles to sustain the metabolism and homeostasis of rapidly growing cells. Recent reports suggest that autophagy may promote tumor cell survival under stress condi-tions and can be an emerging target for cancer therapy. Autophagy inhibitor combined with TMZ can induce glioblastoma cell death and improve the radiotherapy efficacy. The Neuropilin-1 (NRP1) is 120 kDa-130 kDa type I integral transmembrane protein. It was originally identified as a co-receptor for the class 3 semaphorins (SEMA3) involved in axon guidance and found to interact with VEGF/VEGFR2 to promote angio-genesis. Recent studies have revealed its much broader roles on tumor progression. In various types of human cancers, NRP1 is often up-regulated and associated with aggressive clinical tumor behaviour. NRP1 overexpression is independently correlated with poor prognosis in human glioma and contributes to balance the glioblastoma cell proliferation and survival. In cancer cells, it interacts with diverse growth factor receptors including TGFR, c-Met, FGFR, EGFR as well as PDGFR to promote their signal-ling pathways in tumor cell survival, proliferation, migration and invasion. Although these functions of NRP1 mainly rely on its ectodomain, the cytoplasmic domain of NRP1 has been recently found to be essential for the internalization of NRP1-binding complex. In addition, the C-terminal SEA sequence on its cytoplasmic domain have potential to bind intracellular PDZ domain-containing molecules. Tyrosine phosphorylation of p130Cas has been identified to regulate the downstream pathways of NRP1, which is dependent on NRP1 intracellular domain. However, the downstream trafficking of NRP1 is poorly understood and its tumor-promoting function relevance remains ambiguous. The p62/Sequestosome 1, encoded by SQSTM1 gene, is an intracellular protein commonly found in inclusion bodies. It is asso-ciated with protein aggregation diseases in liver and brain. Owing to its ability to interact with multiple important cellular intermedi-ates, it works as a ‘hub’ adaptor linked to nuclear factor-kappaB (NF-κB) activation, protein aggregates formation, selective au-tophagy, adipogenesis and tumorigenesis. The p62 has a critical role on autophagy via regulating the collection and delivery of ubiquitinylated cargos to the autophagosome via its PB1, UBA and LIR domains. On the other hand, recent study has revealed a new role of p62 as a negative regulator in the autophagy regulation. High level of p62 is able to suppress the autophagy by pro-moting mTORC1 activation. This route forms a feed-forward loop for increasing level of p62 due to the reduced autophagy. Thus, p62 plays a critical role in regulation of autophagy. Here we observed that suppression of NRP1 in glioblastoma cell clearly exhibits a defected autophagy accompanied by marked accumulation of p62, the autophagic adaptor. Overexpression of NRP1 by glioblastoma cells shows enhanced autophagy flux. These data suggests the role of NRP1 in autophagy promotion. In addition, we mapped out that p62 binds to the cytoplasmic domain of NRP1 mediating its pro-autophagy effects. PB1 domain of p62 overexpression enhances the p62-positive aggregates and NRP1/p62 interaction. Taken together, our results define a novel role of NRP1 in the regulation of autophagy through its association with p62. In summary, our present results provide novel insights into the molecular basis of the emerging interplay between NRP1 and autophagy, the identification of a new cytoplasmic protein that binding to intracellular domain of NRP1 and the implications of the p62-mediated signalling loop for NRP1-promoted autophagy in GBMs. Since efforts to inhibit autophagy to improve GBM thera-py have thereby attracted great interest, our findings may provide valuable clues for future cancer therapeutic strategies.

Gliomas are the most common malignant brain tumours. The most aggressive and lethal type of glioma is glioblastoma. It has a dismal prognosis, and, despite aggressive treatment, the average patient survival is 1-2 years. Although glioblastoma has a heavy impact on individuals and their families, as well as on healthcare systems, our current lack of mechanistic knowledge hinders the development of improved treatments and diagnostics. Recent studies showed that glutaminolysis, a metabolic pathway utilizing glutamine to produce α-ketoglutarate, is promoted in tumour cells, suggesting a significant role of α-ketoglutarate concentration in tumour progression. Therefore, I hypothesise that reduction of α-ketoglutarate concentration in glioblastoma might suppress glioblastoma aggressiveness. To address this hypothesis, I focus on another metabolic pathway controlling α-ketoglutarate concentration, namely the GABA metabolism. Here, I show that the expression of ABAT and GAD1, which encode rate-limiting enzymes of the GABA metabolism, is associated with the lower-grade of glioma and a better prognosis for patients. Interestingly the expression of ABAT and GAD1 negatively correlates with the expression of CD109, a glioma stemness marker. Furthermore, suppression of glioblastoma stemness by CD109 silencing induces ABAT and GAD1 expression. Taken together these results suggest that the upregulation of the GABA metabolism reduces glioblastoma stemness and proliferation. In future, I am planning to examine the effect of ABAT and GAD1 overexpression and knockdown on glioblastoma stemness and proliferation, as well as the underlying molecular mechanisms to understand how the GABA metabolism suppresses the glioblastoma progression.

New treatment methods are urgently needed for glioblastoma (GBM), the most common malignant primary brain tumor in adults, that currently lacks any curative treatment. Targeted therapeutic approaches have shown promising results already, but common drug delivery vehicles come with efficacy issues and are restricted by their safety and toxicity profiles. Exosomes, cell-produced nanosized vesicles, have emerged as a new potential carrier for gene therapies in cancer treatment due to their natural material transport properties, biocompatibility, and specificity in transporting cargo to the target cells. These extracellular vesicles have the additional advantage of being able to cross the blood-brain-barrier (BBB), which makes them especially valuable for brain malignancies, such as glioblastomas. So far, gene therapy approaches in exosomes have focused on RNA in cancer treatment, but research findings are limited with plasmid-based gene therapies using exosomes. The main concern has been whether the increased plasmid size would decrease the transfection efficiency of the plasmid into the exosomes. This study aimed at setting-up exosomes as plasmid-based gene therapy nanocarriers. To achieve this, different plasmid-based gene therapies were tested, including the targeting of common aberrations of GBM cells to impair proliferation and the use of cytotoxins to induce apoptosis in the target cells. The plasmids were transfected into exosomes and subsequently inoculated into patient-derived glioblastoma cells with the aim of decreasing the number of glioblastoma cells. The findings of this study demonstrate a successful set-up of an exosome-based gene therapy in patient-derived glioblastoma cells by using engineered HEK293FT cell derived exosomes consisting of a plasmid-based combination gene therapy encoding the cytotoxins Granzyme B and Diphtheria toxin fragment A.