Emerging concepts in glioma biology: implications for clinical protocols and rational treatment strategies

Systems Medicine for Precise Targeting of Glioblastoma

Glioblastoma (GBM) is a malignant cancer that is fatal even after standard therapy and the effects of current available therapeutics are not promising due its complex and evolving epigenetic and genetic profile. The mysteries that lead to GBM intratumoral heterogeneity and subtype transitions are not entirely clear. Systems medicine is an approach to view the patient in a whole picture integrating systems biology and synthetic biology along with computational techniques. Since the GBM oncogenesis involves genetic mutations, various therapies including gene therapeutics based on CRISPR-Cas technique, MicroRNAs, and implanted synthetic cells endowed with synthetic circuits against GBM with neural stem cells and mesenchymal stem cells acting as potential vehicles carrying therapeutics via the intranasal route, avoiding the risks of invasive methods in order to reach the GBM cells in the brain are discussed and proposed in this review. Systems medicine approach is a rather novel strategy, and since the GBM of a patient is complex and unique, thus to devise an individualized treatment strategy to tailor personalized multimodal treatments for the individual patient taking into account the phenotype of the GBM, the unique body health profile of the patient and individual responses according to the systems medicine concept might show potential to achieve optimum effects.

Coronavirus disease-19 is associated with decreased treatment access and worsened outcomes in malignant brain tumor patients

Background

The global coronavirus disease-19 (COVID-19) pandemic has resulted in procedural delays around the world; however, timely and aggressive surgical resection for malignant brain tumor patients is essential for outcome optimization. To investigate the association between COVID-19 and outcomes of these patients, we queried the 2020 National Inpatient Sample (NIS) for differences in rates of surgical resection, time to surgery, mortality, and discharge disposition between patients with and without confirmed COVID-19 infection.

Methods

Patient data were taken from the NIS from April 2020 to December 2020. COVID-19 diagnosis was determined with the International Classification of Diseases, Tenth Revision, Clinical Modification code U07.1.

Results

A total of 30,671 malignant brain tumor patients met inclusion criteria and 738 (2.4%) patients had a confirmed COVID-19 diagnosis. COVID-19-positive patients had lower likelihood of receiving surgery (Odds ratio [OR] 0.43, 95% confidence interval [CI] 0.29-0.63, P < 0.0001), increased likelihood of mortality (OR 2.18, 95% CI 1.78-2.66, P < 0.0001), and increased likelihood of non-routine discharge (OR 1.25, 95% CI 1.13-1.39, P < 0.0001). Notably, COVID patients receiving surgery were not associated with surgical delay (P = 0.17).

Conclusion

COVID-19 infection was associated with worse patient outcome in malignant brain tumor patients, including decreased likelihood of receiving surgery, increased likelihood of mortality, and increased likelihood of non-routine discharge. Our study highlights the need to balance the risks and benefits of delaying surgery for malignant brain tumor patients with COVID-19. Although the COVID-19 pandemic is no longer a public health emergency, understanding the pandemic's impact on outcome provides important insight in effective triage for these patients in the situations where resources are limited.

Rabies Virus Glycoprotein-Mediated Transportation and T Cell Infiltration to Brain Tumor by Magnetoelectric Gold Yarnballs

T lymphocyte infiltration with immunotherapy potentially suppresses most devastating brain tumors. However, local immune privilege and tumor heterogeneity usually limit the penetration of immune cells and therapeutic agents into brain tumors, leading to tumor recurrence after treatment. Here, a rabies virus glycoprotein (RVG)-camouflaged gold yarnball (RVG@GY) that can boost the targeting efficiency at a brain tumor via dual hierarchy- and RVG-mediated spinal cord transportation, facilitating the decrease of tumor heterogeneity for T cell infiltration, is developed. Upon magnetoelectric irradiation, the electron current generated on the GYs activates the electrolytic penetration of palbociclib-loaded dendrimer (Den[Pb]) deep into tumors. In addition, the high-density GYs at brain tumors also induces the disruption of cell-cell interactions and T cell infiltration. The integration of the electrolytic effects and T cell infiltration promoted by drug-loaded RVG@GYs deep in the brain tumor elicits sufficient T cell numbers and effectively prolongs the survival rate of mice with orthotopic brain tumors.

Impact of atorvastatin loaded exosome as an anti-glioblastoma carrier to induce apoptosis of U87 cancer cells in 3D culture model

Exosomes (EXOs) are naturally occurring nanosized lipid bilayers that can be efficiently used as a drug delivery system to carry small pharmaceutical, biological molecules and pass major biological barriers such as the blood-brain barrier. It was hypothesized that EXOs derived from human endometrial stem cells (hEnSCs-EXOs) can be utilized as a drug carrier to enhance tumor-targeting drugs, especially for those have low solubility and limited oral bioactivity. In this study, atorvastatin (Ato) loaded EXOs (AtoEXOs) was prepared and characterized for its physical and biological activities in tumor growth suppression of 3 D glioblastoma model. The AtoEXOs were obtained in different methods to maximize drug encapsulation efficacy. The characterization of AtoEXOs was performed for its size, stability, drug release, and in vitro anti-tumor efficacy evaluated comprising inhibition of proliferation, apoptosis induction of tumor cells. Expression of apoptotic genes by Real time PCR, Annexin V/PI, tunnel assay was studied after 72 h exposing U87 cells where encapsulated in matrigel in different concentrations of AtoEXOs (5, 10 μM). The results showed that the prepared AtoEXOs possessed diameter ranging from 30-150 nm, satisfying stability and sustainable Ato release rate. The AtoEXOs was up taken by U87 and generated significant apoptotic effects while this inhibited tumor growth of U87 cells. Altogether, produced AtoEXOs formulation due to its therapeutic efficacy has the potential to be an adaptable approach to treat glioblastoma brain tumors.

Electrotaxis of Glioblastoma and Medulloblastoma Spheroidal Aggregates

Treatment of neuroepithelial cancers remains a daunting clinical challenge, particularly due to an inability to address rampant invasion deep into eloquent regions of the brain. Given the lack of access, and the dispersed nature of brain tumor cells, we explore the possibility of electric fields inducing directed tumor cell migration. In this study we investigate the properties of populations of brain cancer undergoing electrotaxis, a phenomenon whereby cells are directed to migrate under control of an electrical field. We investigate two cell lines for glioblastoma and medulloblastoma (U87mg & DAOY, respectively), plated as spheroidal aggregates in Matrigel-filled electrotaxis channels, and report opposing electrotactic responses. To further understand electrotactic migration of tumor cells, we performed RNA-sequencing for pathway discovery to identify signaling that is differentially affected by the exposure of direct-current electrical fields. Further, using selective pharmacological inhibition assays, focused on the PI3K/mTOR/AKT signaling axis, we validate whether there is a causal relationship to electrotaxis and these mechanisms of action. We find that U87 mg electrotaxis is abolished under pharmacological inhibition of PI3Kγ, mTOR, AKT and ErbB2 signaling, whereas DAOY cell electrotaxis was not attenuated by these or other pathways evaluated.

Engineering challenges for brain tumor immunotherapy

Malignant brain tumors represent one of the most devastating forms of cancer with abject survival rates that have not changed in the past 60years. This is partly because the brain is a critical organ, and poses unique anatomical, physiological, and immunological barriers. The unique interplay of these barriers also provides an opportunity for creative engineering solutions. Cancer immunotherapy, a means of harnessing the host immune system for anti-tumor efficacy, is becoming a standard approach for treating many cancers. However, its use in brain tumors is not widespread. This review discusses the current approaches, and hurdles to these approaches in treating brain tumors, with a focus on immunotherapies. We identify critical barriers to immunoengineering brain tumor therapies and discuss possible solutions to these challenges.

Guiding intracortical brain tumour cells to an extracortical cytotoxic hydrogel using aligned polymeric nanofibres

Glioblastoma multiforme is an aggressive, invasive brain tumour with a poor survival rate. Available treatments are ineffective and some tumours remain inoperable because of their size or location. The tumours are known to invade and migrate along white matter tracts and blood vessels. Here, we exploit this characteristic of glioblastoma multiforme by engineering aligned polycaprolactone (PCL)-based nanofibres for tumour cells to invade and, hence, guide cells away from the primary tumour site to an extracortical location. This extracortial sink is a cyclopamine drug-conjugated, collagen-based hydrogel. When aligned PCL-nanofibre films in a PCL/polyurethane carrier conduit were inserted in the vicinity of an intracortical human U87MG glioblastoma xenograft, a significant number of human glioblastoma cells migrated along the aligned nanofibre films and underwent apoptosis in the extracortical hydrogel. Tumour volume in the brain was significantly lower following insertion of aligned nanofibre implants compared with the application of smooth fibres or no implants.

A novel therapeutic system for malignant glioma: nanoformulation, pharmacokinetic, and anticancer properties of cell-nano-drug delivery

Macrophage carriage, release, and antitumor activities of polymeric nanoformulated paclitaxel (PTX) were developed as a novel delivery system for malignant glioma. To achieve this goal, the authors synthesized PTX-loaded nanoformulations (nano-PTX), then investigated their uptake, release, and toxicological properties. Chemosensitivity was significant in U87 cells (P < 0.05) at concentrations from 10(-4) to 10(-8) M following 72 hours' exposure to bone-marrow-derived macrophages (BMM)-nano-PTX in comparison with treatment with nano-PTX alone. The most significant reductions in U87 cell viability (P < 0.05) were observed in the transwell cocultures containing BMM-nano-PTX. Limited toxicity to BMM was observed at the same concentrations. BMM functions were tested by analysis of microtubules and actin filaments, as the cytoarchitecture, demonstrating a similar cytoskeleton pattern before and after nano-PTX was loaded into cells. This data indicate that nanoformulations of PTX facilitate cell uptake, delay toxicity, and show improved therapeutic efficacy by BMM-nano-PTX delivery.

FROM THE CLINICAL EDITOR

In this study the delivery, release, and antitumor activity of polymeric nanoformulated paclitaxel carried by macrophages are described as a novel and efficient system for treatment of resistant malignant glioma.

WITHDRAWN: A novel therapeutic system for malignant glioma: nanoformulation, pharmacokinetic, and anticancer properties of cell-nano-drug delivery

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Preliminary report on tumor stem cell/B cell hybridoma vaccine for recurrent glioblastoma multiforme

BACKGROUND

Glioblastoma multiforme (GBM), the most aggressive glioma, presents with a rapid evolution and relapse within the first year, which is attributed to the persistence of tumor stem cells (TSC) and the escape of immune surveillance. Mixed leukocyte culture (MLC) cytoimplant has been shown to function as a powerful intratumor pro-inflammatory cytokine pump. Tumor B-cell hybridoma (TBH) vaccines have been shown to function as antigen-presenting cells. We evaluated the toxicity and efficiency of each treatment alone and in combination.

PATIENTS AND METHODS

In an open study, 12 consecutive patients were evenly divided into 3 groups, each group receiving 3 different treatments. Patients in Group 1 were treated, after diagnosis, with debulking surgery (DS)+radiotherapy (Rx), and after the first relapse underwent DS+MLC treatment. Patients in Group 2 were similarly treated but after the first relapse underwent DS+MLC+TBH. Finally, patients in Group 3 were similarly treated but after the first relapse underwent DS+TBH. Nestin PAP stain assessed TSC participation in TBH.

RESULTS

Treatment with MLC had strong and rapid therapeutic effects, but was limited in duration and induced various degrees of brain inflammation. Treatment with MLC+TBH acted synergistically, provoking a rapid, strong and lasting therapeutic response but also generating different degrees of brain inflammation. A lasting therapeutic effect without generating high degrees of brain inflammation occurred in patients treated with TBH vaccine alone.

CONCLUSION

TSC vaccine consisting of TBH alone seems to have potent adjuvant reactions overcoming both persistence of tumor stem cells and immune escape of GBM without provoking an encephalitic reaction.

De novo induction of genetically engineered brain tumors in mice using plasmid DNA

Spontaneous mouse models of cancer show promise to more accurately recapitulate human disease and predict clinical efficacy. Transgenic mice or viral vectors have been required to generate spontaneous models of glioma, a lethal brain tumor, because nonviral gene transfer is typically transient. To overcome this constraint, we used the Sleeping Beauty transposable element to achieve chromosomal integration of human oncogenes into endogenous brain cells of immunocompetent mice. Genetically engineered, spontaneous brain tumors were induced with plasmid DNA in a matter of weeks in three separate mouse strains. The phenotype of tumors was influenced by the combination of oncogenes delivered, resembling human astrocytoma or glioblastoma in the majority of cases. At least five different genes can be cotransfected simultaneously including reporters, allowing measurement of tumor viability by in vivo imaging. This model can accelerate brain tumor research in a variety of ways such as generation of "humanized" models for high throughput drug screening and candidate gene validation with exceptional speed and flexibility.

Persistence of CD133+ cells in human and mouse glioma cell lines: detailed characterization of GL261 glioma cells with cancer stem cell-like properties

The concept of cancer stem cells suggests that there are malignant stem-like cells within a tumor that are responsible for tumor renewal and resistance to cytotoxic therapies. Studies have identified glioma stem-like cells that extrude Hoechst 33342 dye, representing a double-negative "side population" (SP) thought to be selectively resistant to drug therapy. A CD133+ stem cell-like subpopulation has been isolated from a human glioma that was enriched for tumor-initiating cells. It is unknown whether CD133+ cells with similar phenotype persist in established glioma cell lines, or if CD133 is a marker of glioma stem-like cells in rodents. We investigated whether CD133+ and SP cells existed in the GL261 cell line, a syngeneic mouse glioma model that is widely used for preclinical and translational research. Intracerebral injection of less than 100 CD133+ GL261 cells formed tumors, whereas it required 10,000 CD133(-) cells to initiate a tumor. CD133+ GL261 cells expressed nestin, formed tumor spheres with high frequency, and differentiated into glial and neuronal-like cells. Similar to GL261, seven human glioma cell lines analyzed also contained a rare CD133+ population. Surprisingly, we found that CD133+ GL261 cells did not reside in the SP, nor did the majority ( approximately 94%) of CD133+ human glioma cells. These results demonstrate that the expression of CD133 in murine glioma cells is associated with enhanced tumorigenicity and a stem-like phenotype. This study also reveals a previously unrecognized level of heterogeneity in glioma cell lines, exposing several populations of cells that have characteristics of cancer stem cells.

Methylation ofO6-Methylguanine DNA Methyltransferase and Loss of Heterozygosity on 19q and/or 17p Are Overlapping Features of Secondary Glioblastomas with Prolonged Survival

PURPOSE

Recent data suggest that methylation of the DNA repair gene O(6)-methylguanine DNA methyltransferase (MGMT), by increasing the chemosensitivity of glioblastoma multiforme, is significantly associated with improved prognosis. Results in contradiction with these findings, however, are present in the literature and the clinical and genetic context framing MGMT methylation is poorly characterized.

EXPERIMENTAL DESIGN

To address these issues, we have investigated the MGMT methylation status, clinical and magnetic resonance imaging characteristics, and relevant genetic features (loss of heterozygosity on 17p and 19q, EGFR amplification, and p53 mutations) in a retrospective study on 86 patients affected by glioblastoma multiforme: 72 patients had a clinical history indicating de novo insurgence of the tumor and the remaining 14 were secondary glioblastoma multiforme.

RESULTS

MGMT methylation was detected by methylation-specific PCR in 41 of 86 cases (47.7%; Meth+). Progression-free survival and overall survival were significantly longer in Meth+ than in Meth- patients [10 versus 7 months (P=0.003, log-rank test) and 18 versus 14 months (P=0.0003, log-rank test), respectively]. Mixed-nodular enhancement at magnetic resonance imaging was significantly more frequent in Meth+ and secondary glioblastoma multiforme and ring enhancement in Meth- and primary glioblastoma multiforme (P<0.005). MGMT methylation was more present in secondary glioblastoma multiforme (P=0.006) and associated with loss of heterozygosity on 17p and/or 19q (P=0.005).

CONCLUSIONS

These observations suggest that MGMT methylation is part of a genetic signature of glioblastomas that developed from lower-grade gliomas.

Intracranial therapy of glioblastoma with the fusion protein DTAT in immunodeficient mice

A gene splicing technique was used to create a hybrid fusion protein DTAT encoding the 390 amino acid portion of diphtheria toxin (DT(390)), a linker, and the downstream 135-amino terminal fragment portion of human urokinase plasminogen activator. DTAT was assembled to target human glioblastoma cell lines in a murine intracranial model. Previously published in vitro studies demonstrated that DTAT was highly selective and toxic to human glioblastoma cell lines in a flank tumor model. The purpose of this study was to determine the toxicity, specificity and possible therapeutic efficacy of DTAT in an intracranial model. Convection enhanced delivery of DTAT resulted in about a 16-fold increase in maximum tolerated dose. Intracranial administration of DTAT on an every-other-day basis in nude mice with established U87 MG brain tumors resulted in significant reductions in tumor volume and significantly prolonged survival (p < 0.0001). Magnetic resonance imaging proved to be a powerful tool in mice and rats for demonstrating tumor growth in a xenograft intracranial model, assessing the efficacy of DTAT in tumor volume reduction and detecting DTAT-associated intracranial toxicity and vascular damage. These results suggest that the DTAT recombinant fusion protein is highly effective in an intracranial model and DTAT might be an effective treatment for glioblastoma.

Expression of MHC I and NK ligands on human CD133+ glioma cells: possible targets of immunotherapy

Mounting evidence suggests that gliomas are comprised of differentiated tumor cells and brain tumor stem cells (BTSCs). BTSCs account for a fraction of total tumor cells, yet are apparently the sole cells capable of tumor initiation and tumor renewal. BTSCs have been identified as the CD133-positive fraction of human glioma, whereas their CD133-negative daughter cells have limited proliferative ability and are not tumorogenic. It is well established that the bulk tumor mass escapes immune surveillance by multiple mechanisms, yet little is known about the immunogenicity of the CD133-positive fraction of the tumor mass. We investigated the immunogenicity of CD133-positive cells in two human astrocytoma and two glioblastoma multiforme samples. Flow cytometry analyses revealed that the majority of CD133-positive cells do not express detectable MHC I or natural killer (NK) cell activating ligands, which may render them resistant to adaptive and innate immune surveillance. Incubating CD133-positive cells in interferon gamma (INF-gamma) significantly increased the percentage of CD133-positive cells that expressed MHC I and NK cell ligands. Furthermore, pretreatment of CD133-positive cells with INF-gamma rendered them sensitive to NK cell-mediated lysis in vitro. There were no consistent differences in immunogenicity between the CD133-positive and CD133-negative cells in these experiments. We conclude that CD133-posistive and CD133-negative glioma cells may be similarly resistant to immune surveillance, but that INF-gamma may partially restore their immunogenicity and potentiate their lysis by NK cells.