Uncovering a novel mechanism whereby NK cells interfere with glioblastoma virotherapy

Despite initial promising results, the success of clinical trials testing oncolytic viruses in glioblastoma patients has been limited. Innate immunity appears to be one among several barriers against successful viral oncolysis. Recent findings suggest a mechanism by which natural killer cells limit the efficacy of oncolytic viruses via natural cytotoxicity receptors

The Gs-Linked Receptor GPR3 Inhibits the Proliferation of Cerebellar Granule Cells during Postnatal Development

BACKGROUND:During postnatal murine and rodent cerebellar development, cerebellar granule precursors (CGP) gradually stop proliferating as they differentiate after migration to the internal granule layer (IGL). Molecular events that govern this program remain to be fully elucidated. GPR3 belongs to a family of Gs-linked receptors that activate cyclic AMP and are abundantly expressed in the adult brain. METHODOLOGY/PRINCIPAL FINDINGS:To investigate the role of this orphan receptor in CGP differentiation, we determined that exogenous GPR3 expression in rat cerebellar granule neurons partially antagonized the proliferative effect of Sonic hedgehog (Shh), while endogenous GPR3 inhibition by siRNA stimulated Shh-induced CGP proliferation. In addition, exogenous GPR3 expression in CGPs correlated with increased p27/kip expression, while GPR3 knock-down led to a decrease in p27/kip expression. In wild-type mice, GPR3 expression increased postnatally and its expression was concentrated in the internal granular layer (IGL). In GPR3 -/- mice, the IGL was widened with increased proliferation of CGPs, as measured by bromodeoxyuridine incorporation. Cell cycle kinetics of GPR3-transfected medulloblastoma cells revealed a G0/G1 block, consistent with cell cycle exit. CONCLUSIONS/SIGNIFICANCE:These results thus indicate that GPR3 is a novel antiproliferative mediator of CGPs in the postnatal development of murine cerebellum

Mutations in glioblastoma oncosuppressive pathways pave the way for oncomodulatory activity of cytomegalovirus

Over the last decade, cytomegalovirus (CMV) has been suggested to promote the development of glioblastoma multiforme (GBM). Recent evidence demonstrates that CMV contributes to the progression of GBM in the context of oncosuppressor gene mutations. This finding provides further insights into the mechanisms whereby CMV exacerbates the malignancy of GBM

Strategies in Gene Therapy for Glioblastoma

Glioblastoma (GBM) is the most aggressive form of brain cancer, with a dismal prognosis and extremely low percentage of survivors. Novel therapies are in dire need to improve the clinical management of these tumors and extend patient survival. Genetic therapies for GBM have been postulated and attempted for the past twenty years, with variable degrees of success in pre-clinical models and clinical trials. Here we review the most common approaches to treat GBM by gene therapy, including strategies to deliver tumor-suppressor genes, suicide genes, immunomodulatory cytokines to improve immune response, and conditionally-replicating oncolytic viruses. The review focuses on the strategies used for gene delivery, including the most common and widely used vehicles (i.e., replicating and non-replicating viruses) as well as novel therapeutic approaches such as stem cell-mediated therapy and nanotechnologies used for gene delivery. We present an overview of these strategies, their targets, different advantages, and challenges for success. Finally, we discuss the potential of gene therapy-based strategies to effectively attack such a complex genetic target as GBM, alone or in combination with conventional therapy

Deciphering the Multifaceted Relationship between Oncolytic Viruses and Natural Killer Cells

Despite active research in virotherapy, this apparently safe modality has not achieved widespread success. The immune response to viral infection appears to be an essential factor that determines the efficacy of oncolytic viral therapy. The challenge is determining whether the viral-elicited immune response is a hindrance or a tool for viral treatment. NK cells are a key component of innate immunity that mediates antiviral immunity while also coordinating tumor clearance. Various reports have suggested that the NK response to oncolytic viral therapy is a critical factor in premature viral clearance while also mediating downstream antitumor immunity. As a result, particular attention should be given to the NK cell response to various oncolytic viral vectors and how their antiviral properties can be suppressed while maintaining tumor clearance. In this review we discuss the current literature on the NK response to oncolytic viral infection and how future studies clarify this intricate response

Pattern Formation of Glioma Cells: Effects of Adhesion

We investigate clustering of malignant glioma cells. \emph{In vitro} experiments in collagen gels identified a cell line that formed clusters in a region of low cell density, whereas a very similar cell line (which lacks an important mutation) did not cluster significantly. We hypothesize that the mutation affects the strength of cell-cell adhesion. We investigate this effect in a new experiment, which follows the clustering dynamics of glioma cells on a surface. We interpret our results in terms of a stochastic model and identify two mechanisms of clustering. First, there is a critical value of the strength of adhesion; above the threshold, large clusters grow from a homogeneous suspension of cells; below it, the system remains homogeneous, similarly to the ordinary phase separation. Second, when cells form a cluster, we have evidence that they increase their proliferation rate. We have successfully reproduced the experimental findings and found that both mechanisms are crucial for cluster formation and growth.Comment: 6 pages, 6 figure

Gene expression profiling of the anti-glioma effect of Cilengitide

Cilengitide (EMD121974), an inhibitor of the adhesive function of integrins, demonstrated preclinical efficacy against malignant glioma. It is speculated that cilengitide can inhibit tumor growth, invasion, and angiogenesis. However, the effects of cilengitide on these processes have not been sufficiently examined. In this study, we investigated the anti-glioma effect of cilengitide using DNA microarray analysis. U87ΔEGFR cells (human malignant glioma cell line) were used for this experiment. The cells were harvested after 16 h of cilengitide treatment, and mRNA was extracted. Gene expression and pathway analyses were performed using a DNA microarray (CodeLink™Human Whole Genome Bioarray). The expression of 265 genes was changed with cilengitide treatment. The expression of 214 genes was up-regulated by more than 4-fold and the expression of 51 genes was down-regulated by more than 4-fold compared to the controls. In pathway analysis, "apoptotic cleavage of cellular proteins" and "TNF receptor signaling pathway" were over-represented. Apoptotic-associated genes such as caspase 8 were up-regulated. Gene expression profiling revealed more detailed mechanism of the anti-glioma effect of cilengitide. Genes associated with apoptosis were over-represented following cilengitide treatment