New treatment options in the management of glioblastoma multiforme: a focus on bevacizumab

Nuclear receptor NR5A2 negatively regulates cell proliferation and tumor growth in nervous system malignancies

Nervous system malignancies are characterized by rapid progression and poor survival rates. These clinical observations underscore the need for novel therapeutic insights and pharmacological targets. To this end, here, we identify the orphan nuclear receptor NR5A2/LRH1 as a negative regulator of cancer cell proliferation and promising pharmacological target for nervous system-related tumors. In particular, clinical data from publicly available databases suggest that high expression levels of NR5A2 are associated with favorable prognosis in patients with glioblastoma and neuroblastoma tumors. Consistently, we experimentally show that NR5A2 is sufficient to strongly suppress proliferation of both human and mouse glioblastoma and neuroblastoma cells without inducing apoptosis. Moreover, short hairpin RNA-mediated knockdown of the basal expression levels of NR5A2 in glioblastoma cells promotes their cell cycle progression. The antiproliferative effect of NR5A2 is mediated by the transcriptional induction of negative regulators of the cell cycle, CDKN1A (encoding for p21cip1), CDKN1B (encoding for p27kip1) and Prox1 Interestingly, two well-established agonists of NR5A2, dilauroyl phosphatidylcholine (DLPC) and diundecanoyl phosphatidylcholine, are able to mimic the antiproliferative action of NR5A2 in human glioblastoma cells via the induction of the same critical genes. Most importantly, treatment with DLPC inhibits glioblastoma tumor growth in vivo in heterotopic and orthotopic xenograft mouse models. These data indicate a tumor suppressor role of NR5A2 in the nervous system and render this nuclear receptor a potential pharmacological target for the treatment of nervous tissue-related tumors.

Current perspectives concerning the multimodal therapy in Glioblastoma

GBM (Glioblastoma) is the most common, malignant type of primary brain tumor. It has a dismal prognosis, with an average life expectancy of less than 15 months. A better understanding of the tumor biology of GBM has been achieved in the past decade and set up new directions in the multimodal therapy by targeting the molecular paths involved in tumor initiation and progression. Invasion is a hallmark of GBM, and targeting the complex invasive mechanism of the tumor is mandatory in order to achieve a satisfactory result in GBM therapy. The goal of this review is to describe the tumor biology and key features of GBM and to provide an up-to-date overview of the current identified molecular alterations involved both in tumorigenesis and tumor progression.

Survival outcome of early versus delayed bevacizumab treatment in patients with recurrent glioblastoma

Bevacizumab (BEV) is widely used for treatment of patients with recurrent glioblastoma. It is not known if there are differences in outcome between early versus delayed BEV treatment of recurrent glioblastoma. We examined the relationship between the time of starting BEV treatment and outcomes in patients with recurrent glioblastoma. In this retrospective chart review, we identified patients with recurrent glioblastoma diagnosed between 2005 and 2011 who were treated with BEV alone or BEV-containing regimens. Data was analyzed to determine overall survival (OS) from time of diagnosis and progression free survival (PFS) from time of starting BEV. A total of 298 patients were identified, 112 patients received early BEV, 133 patients received delayed BEV, and 53 patients were excluded because they either progressed within 3 months of radiation or received BEV at the time of diagnosis. There was no significant difference in PFS between patients that received early BEV and those that received delayed BEV (5.2 vs. 4.3 months, p = 0.2). Patients treated with delayed BEV had longer OS when compared to those treated with early BEV (25.9 vs. 20.8 months, p = 0.005). In patients with recurrent glioblastoma, there was no significant difference in PFS from the time of starting BEV between early and delayed BEV. Although patients treated with delayed BEV seemed to have longer OS, a conclusion regarding OS outcome requires further prospective trials. These results may indicate that delaying treatment with BEV is not detrimental for survival of patients with recurrent glioblastoma.

Nanoparticles for hyperthermic therapy: synthesis strategies and applications in glioblastoma

Glioblastoma multiforme (GBM) is the most common and most aggressive malignant primary brain tumor in humans. Current GBM treatment includes surgery, radiation therapy, and chemotherapy, sometimes supplemented with novel therapies. Despite recent advances, survival of GBM patients remains poor. Major challenges in GBM treatment are drug delivery across the blood–brain barrier, restriction of damage to healthy brain tissues, and limitation of resistance to therapies. This article reviews recent advances in the application of magnetic nanoparticles (MNPs), gold nanorods (GNRs), and carbon nanotubes (CNTs) for hyperthermia ablation of GBM. First, the article introduces GBM, its current treatment, and hyperthermia as a potential modality for the management of GBM. Second, it introduces MNPs, GNRs, and CNTs as inorganic agents to induce hyperthermia in GBM. Third, it discusses different methodologies for synthesis of each inorganic agent. Finally, it reviews in vitro and in vivo studies in which MNPs, GNRs, and CNTs have been applied for hyperthermia ablation and drug delivery in GBM.

Cancer radioimmunotherapy

Targeting of radionuclides with antibodies, or radioimmunotherapy, has been an active field of research spanning nearly 50 years, evolving with advancing technologies in molecular biology and chemistry, and with many important preclinical and clinical studies illustrating the benefits, but also the challenges, which all forms of targeted therapies face. There are currently two radiolabeled antibodies approved for the treatment of non-Hodgkin lymphoma, but radioimmunotherapy of solid tumors remains a challenge. Novel antibody constructs, focusing on treatment of localized and minimal disease, and pretargeting are all promising new approaches that are currently under investigation.

Glioblastoma multiforme: Molecular characterization and current treatment strategy (Review)

Glioblastoma multiforme (GBM) is the most common and lethal malignant primary brain tumor. It is classified by the World Health Organization (WHO) in the group of diffusely infiltrating astrocytomas, representing up to 50% of all primary brain gliomas, and carries the poorest prognosis. Aberrant genetic events and signaling pathways have clearly demonstrated that GBM is highly anaplastic and a morphologically highly heterogeneous tumor. Understanding the genetic alterations, specific molecular biomarkers and proliferative pathways may promote therapeutic development for the management of GBM. Age, Karnofsky performance score, histology, position and the extent of tumor resection have been identified as potential prognostic factors for patients with GBM. In this study, we review the molecular characterization of tumor cells, the current standard of care for patients diagnosed with GBM, including gross or near-total resection of the tumor, followed by radiotherapy, stereotactic brachytherapy, chemotherapy and new targeted therapies. Thus, we conclude that multimodal approaches for the treatment of patients with GBM may significantly improve their prognoses.

Brain tumor targeting of magnetic nanoparticles for potential drug delivery: effect of administration route and magnetic field topography

Our previous studies demonstrated feasibility of magnetically-mediated retention of iron oxide nanoparticles in brain tumors after intravascular administration. The purpose of this study was to elucidate strategies for further improvement of this promising approach. In particular, we explored administration of the nanoparticles via a non-occluded carotid artery as a way to increase the passive exposure of tumor vasculature to nanoparticles for subsequent magnetic entrapment. However, aggregation of nanoparticles in the afferent vasculature interfered with tumor targeting. The magnetic setup employed in our experiments was found to generate a relatively uniform magnetic flux density over a broad range, exposing the region of the afferent vasculature to high magnetic force. To overcome this problem, the magnetic setup was modified with a 9-mm diameter cylindrical NdFeB magnet to exhibit steeper magnetic field topography. Six-fold reduction of the magnetic force at the injection site, achieved with this modification, alleviated the aggregation problem under the conditions of intact carotid blood flow. Using this setup, carotid administration was found to present 1.8-fold increase in nanoparticle accumulation in glioma compared to the intravenous route at 350mT. This increase was found to be in reasonable agreement with the theoretically estimated 1.9-fold advantage of carotid administration, R(d). The developed approach is expected to present an even greater advantage when applied to drug-loaded nanoparticles exhibiting higher values of R(d).

hMSC-mediated concurrent delivery of endostatin and carboxylesterase to mouse xenografts suppresses glioma initiation and recurrence

Glioma stem cells (GSCs) are known to be maintained within a "vascular niche"; thereby, disruption of this microenvironment using antiangiogenesis agents is a promising therapeutic modality. However, this regimen leads to treatment failure and tumor recurrence in patients with glioblastoma multiforme (GBM). Therefore, more effective therapeutic approaches that can eradicate GSCs and the bulk tumors are needed. Toward this goal, we examined the antitumor effects of an antiangiogenesis approach combined with conventional chemotherapy on suppressing glioma xenograft growth. We established three genetically engineered mesenchymal stem cell (MSC) lines (GE-AF-MSCs) by stably transducing the gene encoding endostatin (an antiangiogenesis factor), the gene encoding secretable form of carboxylesterase 2 (sCE2, a prodrug-activating enzyme), or a mixture of both genes. Among the three GE-AF-MSC cell lines, injection of amniotic fluid (AF)-MSCs-endostatin-sCE2 cells into U87MG-EGFRvIII-driven orthotopic brain tumor and postsurgery tumor recurrence models, and subsequent CPT11 treatment yielded the strongest antitumor responses, including diminished angiogenesis, increased cell death, and a reduced Nestin-positive GSC population. Therefore, our antitumor strategy provides a novel basis for designing stem cell-mediated therapeutic approaches to target and eradicate GSCs and the bulk tumors.

Comparison of corticotropin-releasing factor, dexamethasone, and temozolomide: treatment efficacy and toxicity in U87 and C6 intracranial gliomas

PURPOSE/EXPERIMENTAL DESIGN: Treatment of cerebral tumors and peritumoral brain edema remains a clinical challenge and is associated with high morbidity and mortality. Dexamethasone is an effective drug for treating brain edema, but it is associated with well-documented side effects. Corticorelin acetate (Xerecept) or human corticotrophin-releasing factor (hCRF) is a comparatively new drug and has been evaluated in two orthotopic glioma models (U87 and C6), by a direct comparison with dexamethasone and temozolomide.

RESULTS

In vitro combination therapy and monotherapy showed a variable response in 6 different glioma cell lines. In vivo studies showed a dose-dependent effect of hCRF (0.03 and 0.1 mg/kg q12h) on survival of U87 intracranial xenograft-bearing animals [median survival: control--41 days (95% CI 25-61); "low-hCRF" 74.5 days (95% CI 41-88); "high-hCRF" >130 days (95% CI not reached)]. Dexamethasone treatment had no effect on survival, but significant toxicity was observed. A survival benefit was observed with temozolomide and temozolomide + hCRF-treated animals but with significant temozolomide toxicity. C6-bearing animals showed no survival benefit, but there were similar treatment toxicities. The difference in hCRF treatment response between U87 and C6 intracranial gliomas can be explained by a difference in receptor expression. RT-PCR identified CRF2r mRNA in U87 xenografts; no CRF receptors were identified in C6 xenografts.

CONCLUSIONS

hCRF was more effective than either dexamethasone or temozolomide in the treatment of U87 xenografts, and results included improved prognosis with long-term survivors and only mild toxicity. The therapeutic efficacy of hCRF seems to be dependent on tumor hCRF receptor (CRFr) expression. These results support further clinical assessment of the therapeutic efficacy of hCRF and levels of CRFr expression in different human gliomas.