The IL13α 2R paves the way for anti-glioma nanotherapy

Glioblastoma (GBM) is one of the most aggressive (grade IV) gliomas characterized by a high rate of recurrence, resistance to therapy and a grim survival prognosis. The long-awaited improvement in GBM patients' survival rates essentially depends on advances in the development of new therapeutic approaches. Recent preclinical studies show that nanoscale materials could greatly contribute to the improvement of diagnosis and management of brain cancers. In the current review, we will discuss how specific features of glioma pathobiology can be employed for designing efficient targeting approaches. Moreover, we will summarize the main evidence for the potential of the IL-13R alpha 2 receptor (IL13α2R) targeting in GBM early diagnosis and experimental therapy.

Metabolome-Driven Regulation of Adenovirus-Induced Cell Death

A viral infection that involves virus invasion, protein synthesis, and virion assembly is typically accompanied by sharp fluctuations in the intracellular levels of metabolites. Under certain conditions, dramatic metabolic shifts can result in various types of cell death. Here, we review different types of adenovirus-induced cell death associated with changes in metabolic profiles of the infected cells. As evidenced by experimental data, in most cases changes in the metabolome precede cell death rather than represent its consequence. In our previous study, the induction of autophagic cell death was observed following adenovirus-mediated lactate production, acetyl-CoA accumulation, and ATP release, while apoptosis was demonstrated to be modulated by alterations in acetate and asparagine metabolism. On the other hand, adenovirus-induced ROS production and ATP depletion were demonstrated to play a significant role in the process of necrotic cell death. Interestingly, the accumulation of ceramide compounds was found to contribute to the induction of all the three types of cell death mentioned above. Eventually, the characterization of metabolite analysis could help in uncovering the molecular mechanism of adenovirus-mediated cell death induction and contribute to the development of efficacious oncolytic adenoviral vectors.

Inhibition of MMP14 potentiates the therapeutic effect of temozolomide and radiation in gliomas

Metalloproteinases are membrane-bound proteins that play a role in the cellular responses to antiglioma therapy. Previously, it has been shown that treatment of glioma cells with temozolomide (TMZ) and radiation (XRT) induces the expression of metalloproteinase 14 (MMP14). To investigate the role of MMP14 in gliomagenesis, we used several chemical inhibitors which affect MMP14 expression. Of all the inhibitors tested, we found that Marimastat not only inhibits the expression of MMP14 in U87 and U251 glioma cells, but also induces cell cycle arrest. To determine the relationship between MMP14 inhibition and alteration of the cell cycle, we used an RNAi technique. Genetic knockdown of MMP14 in U87 and U251 glioma cells induced G₂/M arrest and decreased proliferation. Mechanistically, we show that TMZ and XRT regulated expression of MMP14 in clinical samples and in vitro models through downregulation of microRNA374. In vivo genetic knockdown of MMP14 significantly decreased tumor growth of glioma xenografts and improved survival of glioma-bearing mice. Moreover, the combination of MMP14 silencing with TMZ and XRT significantly improved the survival of glioma-bearing mice compared to a single modality treatment group. Therefore, we show that the inhibition of MMP14 sensitizes tumor cells to TMZ and XRT and could be used as a future strategy for antiglioma therapy.

Glioblastoma remains an incurable form of brain cancer. In this manuscript, we show that inhibition of MMP14 can potentiate the efficacy of current standard of care which includes chemo- and radiotherapy.

Localization of the N-terminus of minor coat protein IIIa in the adenovirus capsid

Minor coat protein IIIa is conserved in all adenoviruses (Ads) and is required for correct viral assembly, but its precise function in capsid organization is unknown. The latest Ad capsid model proposes that IIIa is located underneath the vertex region. To obtain experimental evidence on the location of IIIa and to further define its role, we engineered the IIIa gene to encode heterologous N-terminal peptide extensions. Recombinant Ad variants with IIIa encoding six-histidine (6His) tag, 6His, and FLAG peptides, or with 6His linked to FLAG with a (Gly(4)Ser)(3) linker were rescued and analyzed for virus yield, capsid incorporation of heterologous peptides, and capsid stability. Longer extensions could not be rescued. Western blot analysis confirmed that the modified IIIa proteins were expressed in infected cells and incorporated into virions. In the Ad encoding the 6His-linker-FLAG-IIIa gene, the 6His tag was present in light particles, but not in mature virions. Immunoelectron microscopy of this virus showed that the FLAG epitope is not accessible to antibodies on the viral particles. Three-dimensional electron microscopy and difference mapping located the IIIa N-terminal extension beneath the vertex complex, wedged at the interface between the penton base and peripentonal hexons, therefore supporting the latest proposed model. The position of the IIIa N-terminus and its low tolerance for modification provide new clues for understanding the role of this minor coat protein in Ad capsid assembly and disassembly.

An adenoviral platform for selective self-assembly and targeted delivery of nanoparticles

Metallic nanoparticles (NPs) can be used for the diagnosis, imaging, and therapy of tumors and cardiovascular disease. However, targeted delivery of NPs to specific cells remains a major limitation for clinical realization of these potential treatment options. Herein, a novel strategy for the specific coupling of NPs to a targeted adenoviral (Ad) platform to deliver NPs to specific cells is defined. Genetic manipulation of the gene-therapy vector is combined with a specific chemical coupling strategy. In particular, a high-affinity interaction between a sequence of six-histidine amino acid residues genetically incorporated into Ad capsid proteins and nickel(II) nitrilotriacetic acid on the surface of gold NPs is employed. The selective self-assembly of gold NPs and Ad vectors into multifunctional platforms does not negatively affect the targeting of Ad to specific cells. This opens the possibility of using Ad vectors for targeted NP delivery, thereby providing a new type of combinatorial approach for the treatment of diseases that involves both nanotechnology and gene therapy.

Enhanced transduction of malignant glioma with a double targeted Ad5/3-RGD fiber-modified adenovirus

Malignant brain tumors remain refractory to adenovirus type 5 (Ad5)-based gene therapy, mostly due to the lack of the primary Ad5 receptor, the coxsackie and adenovirus receptor, on brain tumor cells. To bypass the dependence on coxsackie and adenovirus receptor for adenoviral entry and infectivity, we used a novel, double targeted Ad5 backbone-based vector carrying a chimeric Ad5/3 fiber with integrin-binding RGD motif incorporated in its Ad3 knob domain. We then tested the new virus in vitro and in vivo in the setting of malignant glioma. Ad5/3-RGD showed a 10-fold increase in gene expression in passaged cell lines and up to 75-fold increase in primary tumors obtained from patients relative to the control. These results were further corroborated in our in vivo human glioma xenograft model, where the Ad5/3-RGD vector showed a 1,000-fold increase in infectivity as compared with the control. Taken together, our findings indicate that Ad5/3-RGD may be a superior vector for applications in glioma gene therapy and therefore warrants further attention in the field of neuro-oncology.

Conserved boxes C and D are essential nucleolar localization elements of U14 and U8 snoRNAs

Sequences necessary for nucleolar targeting were identified in Box C/D small nucleolar RNAs (snoRNAs) by fluorescence microscopy. Nucleolar preparations were examined after injecting fluorescein-labelled wild-type and mutated U14 or U8 snoRNA into Xenopus oocyte nuclei. Regions in U14 snoRNA that are complementary to 18S rRNA and necessary for rRNA processing and methylation are not required for nucleolar localization. Truncated U14 molecules containing Boxes C and D with or without the terminal stem localized efficiently. Nucleolar localization was abolished upon mutating just one or two nucleotides within Boxes C and D. Moreover, the spatial position of Boxes C or D in the molecule is essential. Mutations in Box C/D of U8 snoRNA also impaired nucleolar localization, suggesting the general importance of Boxes C and D as nucleolar localization sequences for Box C/D snoRNAs. U14 snoRNA is shown to be required for 18S rRNA production in vertebrates.

U3 snoRNA may recycle through different compartments of the nucleolus

A model is proposed in which U3 small nucleolar RNA (snoRNA) is recruited from an inactive, stored form in the dense fibrillar component (DFC) of the nucleolus to an active form that is associated with the initial ribosomal RNA (rRNA) precursor. The initial steps of rRNA processing occur in the DFC, and then it is proposed that the U3 snoRNA moves with intermediates in rRNA processing from the DFC to the granular component (GC) of the nucleolus. The nucleolar protein fibrillarin is located primarily in the DFC, and it is suggested that the complex of fibrillarin and U3 snoRNA dissociates when U3 snoRNA transits to the GC. Finally, when U3 snoRNA is released from the processed rRNA, the tether holding the rRNA in the nucleolus is broken and rRNA can then be exported from the nucleolus to the cytoplasm. U3 snoRNA is hypothesized to recycle back from the GC to the DFC where it is stored until future association with another initial rRNA precursor. Data supporting this model are summarized. U3 snoRNA is also stored in the coiled body of interphase cells and in the nucleolar remnants and prenucleolar bodies of mitotic cells, and there may be some similarity in the binding sites for stored U3 snoRNA in the DFC and in these structures.

Pyrimidine tract binding protein strongly stimulates in vitro encephalomyocarditis virus RNA translation at the level of preinitiation complex formation

Cellular protein p57/58, now known to be identical to polypyrimidine tract binding protein (PTB), has earlier been shown to specifically bind to the internal ribosome entry sites (IRES) of encephalomyocarditis virus (EMCV) and some other picornaviral RNAs. To elucidate its relevance to the internal initiation, the effect of cloned purified PTB on EMCV IRES directed translation was studied in cytoplasmic extracts of Krebs-2 ascites carcinoma cells partially depleted of endogenous PTB. Addition of PTB to such extracts resulted in a strong stimulation of translation of a beta-glucuronidase (GUS) reporter cistron fused to the EMCV IRES, but had no effect on translation of capped mRNAs, such as beta-globin, and tobacco mosaic virus (TMV) RNAs. PTB was found to exert its effect at the level of 48S pre-initiation complex formation.