Targeted therapy for malignant gliomas

LncRNA RP1-86C11.7 exacerbates the glioma progression and oncogenicity by hsa-miR-144-3p/TFRC signaling

•

High level of TFRC promotes the glioma development.

•

Hsa-miR-144-3p inhibitor glioma growth by targeting TFRC.

•

LncRNA RP1-86C11.7 exacerbates glioma progression through sponging to hsa-miR-144-3p, resulting in TFRC upregulation.

Glioblastoma (GBM) remains the most common and malignant tumor of the human central nervous system. Increasing evidence has highlighted that tumor cells with high transferrin receptor (TFRC) expression show advantages in growth. Long noncoding RNAs (lncRNAs) are related to glioma progression by mediating microRNAs (miRNAs). However, the underlying mechanism among TFRC, miRNA and lncRNA in GBM is limited. In the current study, we identified a new lncRNA-induced signaling mechanism that regulates the TFRC levels in GBM. The TFRC level was higher in glioma cell lines, and elevated TFRC expression promoted the proliferation and survival of glioma cells. Further study showed that hsa-miR-144a-3p bound to the 3′-UTR of TFRC mRNA and inhibited its expression, preventing the malignant properties of glioma cells, such as proliferation and survival. We also found that the lncRNA RP1-86C11.7 sponges hsa-miR-144-3p to suppress its protective role in glioma. RP1-86C11.7 overexpression in glioma cells elevated TFRC expression, increased the intracellular free iron level, and deteriorated oncogenicity, with a significant reduction in hsa-miR-144-3p. By contrast, silencing RP1-86C11.7 upregulated the hsa-miR-144-3p level, resulting in decreased TFRC expression and repressed glioma progression. However, the effect of silencing RP1-86C11.7 was reversed with simultaneous hsa-miR-144-3p inhibitor treatment: the TFRC level, intracellular iron level and proliferation in glioma cells increased. Mechanistically, our data indicated that RP1-86C11.7 exacerbates the malignant behavior of glioma through the hsa-miR-144-3p/TFRC axis. RP1-86C11.7 may be a potential biomarker or target to treat glioma in the future.

Angiopep-2/IP10-EGFRvIIIscFv modified nanoparticles and CTL synergistically inhibit malignant glioblastoma

Preparation of agents that can successfully traverse the blood-brain-barrier (BBB) is a key challenge in brain cancer therapeutics. In this study, angiopep-2 was used as a brain-targeting peptide for preparing multifunctional Angiopep-2-modified poly nanoparticles, angiopep-2 and IP10-EGFRvIIIscFv fusion protein modified nanoparticles. In vitro experiments showed a greater uptake of Angiopep-2 modified nanoparticles, also angiopep-2 and IP10-EGFRvIIIscFv fusion protein modified nanoparticles by bEnd.3 cells versus nanoparticles and nanoparticles modified by IP10-EGFRvIIIscFv. Angiopep-2 and IP10-EGFRvIIIscFv fusion protein modified nanoparticles accumulated in brain tissue after intravenous injection and recruited activated CD8⁺ T lymphocytes to location of glioblastoma cells. In vivo experiments to assess anti-glioblastoma effect of angiopep-2 and IP10-EGFRvIIIscFv fusion protein modified nanoparticles showed significantly reduced tumor volume in angiopep-2 and IP10-EGFRvIIIscFv fusion protein modified nanoparticles⁺ CD8⁺ cytotoxic T lymphocytes group versus in NPs modified by IP10-EGFRvIIIscFv⁺ CD8⁺ cytotoxic T lymphocytes, CD8⁺ cytotoxic T lymphocytes, Angiopep-2 modified nanoparticles⁺ CD8⁺ cytotoxic T lymphocytes, angiopep-2 and IP10-EGFRvIIIscFv fusion protein modified nanoparticles and PBS groups. Leukocytes infiltrated in brain tissues showed strong anti-glioblastoma activity in angiopep-2 and IP10-EGFRvIIIscFv fusion protein modified nanoparticles⁺ CD8⁺ cytotoxic T lymphocytes treated mice. Thus, angiopep-2 and IP10-EGFRvIIIscFv fusion protein modified nanoparticles may be useful for brain-targeted delivery and recruitment of activated CD8⁺ T lymphocytes to glioblastoma cells.

Ligand-dependent EphB1 signaling suppresses glioma invasion and correlates with patient survival

BACKGROUND

Extensive evidence implicates the Eph receptor family of tyrosine kinases and its ligand, ephrin, in glioma invasion, but it remains incompletely understood how these receptors affect chemotactic behavior of glioma. We sought to identify the Eph family members that correlate with patients' survival and to reveal the function of Eph in glioma invasion.

METHODS

Clinical relevance of EphB genes was confirmed in a clinically annotated expression data set of 195 brain biopsy specimens. The function of EphB was analyzed in vitro and in vivo.

RESULTS

Levels of mRNA of certain EphB members were significantly different in histological grades of glioma. According to Kaplan-Meier analysis, only the EphB1 level among 5 members of EphB emerged to be a powerful predictor of favorable survival in malignant glioma (n = 97, P = .0048), although the levels of EphB1 expression did not vary across the tumor grades. Immunoprecipitation showed that tyrosine phosphorylated EphB1 was not detected in all glioma cells tested. Forced overexpression and autophosphorylation of EphB1 in low expressor cell lines (U251, U87) did not affect cell migration or invasion in vitro, whereas EphB1 phosphorylation induced by ephrin-B2/Fc significantly decreased migration and invasion. Cells expressing ephrin-B2 showed noteworthy morphological changes consistent with migration induction; this alteration was negated by EphB1 overexpression. Concomitantly, overexpression of EphB1 abrogated the increased migration and invasion induced by ephrin-B2 in vitro and in vivo.

CONCLUSIONS

These data suggest that ligand-dependent EphB1 signaling negatively regulates glioma cell invasion, identifying EphB1 as a favorable prognostic factor in malignant glioma.

Targeted killing effects of double CD and TK suicide genes controlled by survivin promoter on gastric cancer cell

Suicide genes such as cytosine deaminase (CD) and herpes simplex virus thymidine kinase (TK) encode products that convert nontoxic substances (prodrugs) into toxic metabolites. Studies in recent years indicated that survivin(sur) expression was associated with the biological behaviors of gastric carcinoma. In the present study, targeted killing effects of double CD and TK suicide genes controlled by survivin promoter on gastric cancer cell were investigated, the recombinant pSCT vector containing CD and TK genes driven by sur promoter was constructed and transfected into SGC-7901 cells. After adding the CCV and 5-FC, the effects of double suicide genes on cell growth, cell cycle and proliferation were determined by MTT assay and flow cytometry (FCM). The results showed that sur promoter could specifically drive the expression of double CD/TK gene in SGC-7901 cells, whereas not in the normal GES-1 cell. After using CCV and 5-FC, the growth of SGC-7901 cells was inhibited. G1 phase proportion was significantly higher in SGC-7901 cells transfected with double suicide genes than the untransfected cells. These results suggest that CD and TK double suicide genes driven by sur promoter could provide a new approach for enhancing selective suicide gene therapy of CD/5-FC for the treatment of advanced gastric carcinoma.

Intratumoral therapy of glioblastoma multiforme using genetically engineered transferrin for drug delivery

Glioblastoma multiforme (GBM) is the most common and lethal primary brain tumor with median survival of only 12 to 15 months under the current standard of care. To both increase tumor specificity and decrease nonspecific side effects, recent experimental strategies in the treatment of GBM have focused on targeting cell surface receptors, including the transferrin (Tf) receptor, that are overexpressed in many cancers. A major limitation of Tf-based therapeutics is the short association of Tf within the cell to deliver its payload. We previously developed two mutant Tf molecules, K206E/R632A Tf and K206E/K534A Tf, in which iron is locked into each of the two homologous lobes. Relative to wild-type Tf, we showed enhanced delivery of diphtheria toxin (DT) from these mutants to a monolayer culture of HeLa cells. Here, we extend the application of our Tf mutants to the treatment of GBM. In vitro treatment of Tf mutants to a monolayer culture of glioma cells showed enhanced cellular association as well as enhanced delivery of conjugated DT. Treatment of GBM xenografts with mutant Tf-conjugated DT resulted in pronounced regression in vivo, indicating their potential use as drug carriers.

Treatment of malignant gliomas with TGF-beta2 antisense oligonucleotides

Antisense oligodeoxynucleotides (AS-ODNs) have been widely used to determine gene function, validate drug targets and as novel therapeutics for human diseases. In this review, we describe the development of AS-ODNs, including their modifications, pharmacokinetics and toxicity in animal models and humans, and their preclinical and clinical development in the therapy of human high-grade gliomas. The most advanced AS-ODN for the therapy of high-grade gliomas is a phosphorothioate-modified AS-ODN, AP 12009 (trabedersen), which targets mRNA encoding TGF-beta2. AP 12009 is administered intratumorally using convection-enhanced delivery. A series of Phase I and II clinical trials have evaluated the toxicity profile and optimal dose of the substance. A randomized, controlled international Phase III study was initiated in March 2009 and will compare trabedersen 10 microM versus conventional alkylating chemotherapy in patients with recurrent or refractory anaplastic astrocytoma after standard radio- and chemotherapy.

Expression of receptor tyrosine kinases VEGFR-1 (FLT-1), VEGFR-2 (KDR), EGFR-1, PDGFRalpha and c-Met in canine primary brain tumours

Inhibition of tumour growth and angiogenesis by targeting key growth factor receptors is a promising therapeutic strategy for central nervous system tumours. Characterization of these growth factor receptors in canine primary brain tumours has not been done. Using quantitative real-time TaqMan polymerase chain reaction (PCR), we evaluated the expression of messenger RNA (mRNA) for five tyrosine kinase growth factor receptors (vascular endothelial growth factor receptor [VEGFR]-1, VEGFR-2, endothelial growth factor receptor [EGFR]-1, platelet-derived growth factor receptor a [PDGFRa], and c-Met) relative to normal cerebral cortex in 66 spontaneous canine primary brain tumours. Increased expression of VEGFR-1 and VEGFR-2 mRNA was greatest in grade IV astrocytomas (glioblastoma multiforme) and grade III (anaplastic) oligodendrogliomas. EGFR-1 mRNA expression was more consistently increased than the other receptors in all tumour types, while increased PDGFRa mRNA expression was mostly restricted to oligodendrogliomas. The similarities in increased expression of these tyrosine kinase growth factor receptors in these canine tumours, as compared to data from their human counterparts, suggest that common molecular mechanisms may be present.

The EGFRvIII variant in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common brain tumour and has the worst prognosis. Epidermal growth factor receptor (EGFR) gene amplification, mutation and re-arrangement (all of which enhance tumour growth, survival, progression and resistance to therapy) are frequently observed in primary GBM. The most common EGFR variant in GBM, the EGFRvIII, is characterised by a deletion of 267 amino acids in the extracellular domain, leading to a receptor which is unable to bind ligand yet is constitutively active. Together with its impaired internalisation and degradation, the EGFRvIII enhances the tumourigenic potential of GBM by activating and sustaining mitogenic, anti-apoptotic and pro-invasive signalling pathways. This EGFRvIII-mediated enhanced tumourigenicity combined with the lack of EGFRvIII expression in normal tissue makes it an ideal candidate for targeted therapy. This review summarizes the current knowledge about the role of EGFRvIII in GBM and discusses therapeutic agents targeting EGFRvIII that are being evaluated as treatments for GBM.

Invadopodia: at the cutting edge of tumour invasion

Invasion of tissues by malignant tumours is facilitated by tumour cell migration and degradation of extracellular matrix (ECM) barriers. Several invasive neoplasms, including head and neck squamous cell carcinoma, breast carcinoma, melanoma and glioma, contain tumour cells that can form actin-rich protrusions with ECM proteolytic activity called invadopodia. These dynamic organelle-like structures adhere to, and digest, collagens, laminins and fibronectin. Invadopodia are dependent on multiple transmembrane, cytoplasmic and secreted proteins engaged in cell adhesion, signal transduction, actin assembly, membrane regulation and ECM proteolysis. Strategies aimed at disrupting invadopodia could form the basis of novel anti-invasive therapies for treating patients. Here we review the molecular basis of invadopodia formation with particular emphasis on the intracellular signaling networks that are essential for invadopodia activity and examine the potential role of these structures in glioma invasion.

Expression of vascular endothelial growth factor in tumors and plasma from dogs with primary intracranial neoplasms

OBJECTIVE

To quantitatively evaluate expression of vascular endothelial growth factor (VEGF) in intracranial tumors in dogs and determine whether relationships exist between circulating and intratumoral VEGF concentrations and tumor type and grade.

ANIMALS

27 dogs with primary intracranial neoplasms and 4 unaffected control dogs.

PROCEDURES

Plasma and brain tumor samples were obtained from each dog, and plasma and intratumoral concentrations of VEGF were measured by use of an ELISA.

RESULTS

Dogs with meningiomas (n = 11) were significantly older than dogs with oligodendrogliomas (7) or astrocytomas (9). Measurable VEGF was detected in all tumors, and a significant negative correlation between age and intratumoral VEGF concentration was detected. Age-adjusted comparisons identified significant differences in intratumoral VEGF concentrations among all tumor types; the highest VEGF concentrations were associated with astrocytomas. Within each tumor type, increasing tumor grade was significantly associated with increasing VEGF expression. Plasma VEGF concentrations were detectable in 9 of 27 dogs; the proportion of dogs with astrocytomas and a detectable circulating VEGF concentration (7/9 dogs) was significantly higher than the proportion of dogs with meningiomas (1/11 dogs) or oligodendrogliomas (1/7 dogs) with a detectable circulating VEGF concentration.

CONCLUSIONS AND CLINICAL RELEVANCE

Overexpression of VEGF appears common in canine astrocytomas, oligodendrogliomas, and meningiomas. In the neoplasms examined, intratumoral VEGF concentrations correlated well with tumor malignancy. The VEGF expression patterns paralleled those of analogous human tumors, providing evidence that dogs are a suitable species in which to study angiogenesis and intracranial neoplasia for human application.

Construction of double suicide genes system controlled by MDR1 promoter with targeted expression in drug-resistant glioma cells

The multiple drug resistance protein (MDR1) is frequently overexpressed in human glioma. The aim of this study is to clone the MDR1 promoter from C6/ADR, construct the double suicide genes expressive vector controlled by MDR1 promoter, and explore its targeted expression in C6/ADR cells. MDR1 promoter from C6/ADR genomic DNA, which was linked with T vector, was amplified by using Polymerase chain reaction (PCR). After cut by NdeI and HindIII, MDR1 promoter was cloned into pcDNA3-TK (thymidine kinase) plasmid. The cytosine deaminase (CD) gene from pcDNA3-CD-TK plasmid was directly cloned into the above vector to construct pcDNA3-MDR1-promoter-CD-TK vector. Then this vector was transfected into C6 and C6/ADR cells respectively by liposome. After selection by G418, the tumor cell lines were stably established. Then these cell lines were examined through PCR and RT-PCR to respectively detect the integration and expression of TK and CD genes. The results showed the length and sequence of MDR1 promoter amplified by PCR were confirmed by DNA sequencing. The pcDNA3-MDR1-promoter-CD-TK expression vectors were constructed successfully. PCR indicated the double suicide genes were integrated into C6 and C6/ADR cells. RT-PCR revealed that CD and TK genes expressed in C6/ADR/CD-TK cells, whereas not in C6/CD-TK cells. In conclusions, construction of expressive vector containing double suicide genes controlled by MDR1 promoter with targeted expression in C6/ADR will provide a sound basis for targeted gene therapy for multidrug resistance (MDR) glioma.

Targeting malignant glioma survival signalling to improve clinical outcomes

Malignant gliomas are common and aggressive brain tumours in adults. Current treatments for glioblastoma multiforme result in a poor median survival of less than 12 months. The blood-brain barrier restricts the delivery of many chemotherapies to the central nervous system, contributing to the failure of treatment. PI3K/Akt and Ras/MAPK pathways have been identified as important oncogenic pathways in these tumours. The PI3K/Akt pathway mediates cell survival and growth, whereas the Ras/MAPK pathway signals cell differentiation, proliferation and anti-apoptosis. Modern targeted therapies include antibodies to circulating growth factors and cell surface receptors, as well as inhibitors of receptor tyrosine kinases and specific intracellular signalling proteins. Monotherapy with most targeted therapies produces only modest efficacy. Better results are achieved in combination with cytotoxic chemotherapies. Future therapeutics should focus on combination therapy with small lipophilic molecules.

Making efficient use of patients in designing phase III trials investigating simultaneously a set of targeted therapies with different targets

Targeted therapies are a recent development in cancer treatment research. As these therapies can only be administered to patients with certain individual characteristics, it is a straightforward idea to investigate several of such therapies simultaneously in a given patient population in order to compare each targeted therapy with the current standard therapy. This raises the question how patients satisfying several characteristics should be handled. We consider in this paper several designs to allocate treatments in a random manner to these patients, such that the evaluation of each single targeted therapy can be based on a simple comparison of patients receiving the targeted therapies versus those receiving the standard therapy within a well defined subgroup of patients satisfying the corresponding characteristic. We show how one can ensure that patients with several characteristics can contribute simultaneously to the evaluation of several targeted therapies and that this is the key point for an efficient use of the patients available. We further discuss some ethical and practical issues in applying the new designs and outline strategies to evaluate the overall effect of all targeted therapies together.

Photodynamic therapy of cerebral glioma – A review Part I – A biological basis

Photodynamic therapy (PDT) has been investigated extensively in the laboratory for decades, and for over 25 years in the clinical environment, establishing it as a useful adjuvant to standard treatments for many cancers. A combination of both photochemical and photobiological processes occur that lead to the eventual selective destruction of the tumour cells. It is a potentially valuable adjuvant therapy that can be used in conjunction with other conventional therapies for the treatment of cerebral glioma. PDT has undergone extensive laboratory studies and clinical trials with a variety of photosensitizers (PS) and tumour models of cerebral glioma. Many environmental and genetically based factors influence the outcome of the PDT response. The biological basis of PDT is discussed with reference to laboratory and preclinical studies.

Protein toxins: intracellular trafficking for targeted therapy

The immunotoxin approach is based on the use of tumor-targeting ligands or antibodies that are linked to the catalytic (toxic) moieties of bacterial or plant protein toxins. In this review, we first discuss the current state of clinical development of immunotoxin approaches describing the results obtained with the two toxins most frequently used: diphtheria and Pseudomonas toxin-derived proteins. In the second part of the review, a novel concept will be presented in which the roles are inverted: nontoxic receptor-binding toxin moieties are used for the targeting of therapeutic and diagnostic compounds to cancer or immune cells. The cell biological basis of these novel types of toxin-based therapeutics will be discussed, and we will summarize ongoing preclinical and clinical testing.