Current review of in vivo GBM rodent models: emphasis on the CNS-1 tumour model

Effect of Rosmarinic Acid on Cell Proliferation, Oxidative Stress, and Apoptosis Pathways in an Animal Model of Induced Glioblastoma Multiforme

BACKGROUND

In brain tumors, the complexity of the pathophysiological processes such as oxidative stress, cell proliferation, angiogenesis, and apoptosis have seriously challenged the definitive treatment. Rosmarinic acid (RA), as a polyphenolic compound, has been found to prevent tumor progression in some aggressive cancers. This study was designed to evaluate the anticancer effects of RA on brain tumors.

METHOD

Rats were divided into six groups. Implantation of C6 glioma cells was carried out in the caudate nucleus of the right hemisphere. RA at doses of 5, 10, and 20 mg/kg (i.p.) was administered to the treatment groups for seven days. Tumor volume (by MRI imaging), locomotor ability, survival time, histological alterations (by H & E staining), expression of p53 and p21 mRNAs (by RT-PCR), activities of antioxidant enzymes (superoxide dismutase [SOD] and catalase [CAT] by assay kits), expression of caspase-3 and VEGF (by immunohistochemical analysis), and TUNEL-positive cells (by tunnel staining) were analyzed.

RESULTS

The results indicated that the RA at a dose of 20 mg/kg reduced the tumor volume, prolonged survival time, increased p53 and p21 mRNAs, attenuated SOD and CAT activities in tumor tissue, elevated caspase-3, and increased the number of TUNEL-positive cells. Furthermore, histological analysis revealed less invasion of tumor cells into the normal parenchyma in rats treated with RA (20 mg/kg).

CONCLUSION

These findings provide evidence that the ability of RA to reduce tumor volume could be related to factors that modulate oxidative stress (SOD and CAT enzymes), cell proliferation (p53 and p21), and apoptosis (caspase-3).

Coagulation proteases and neurotransmitters in pathogenicity of glioblastoma multiforme

Glioblastoma is an aggressive type of cancer that begins in cells called astrocytes that support nerve cells that can occur in the brain or spinal cord. It can form in the brain or spinal cord. Despite the variety of modern therapies against GBM, it is still a deadly disease. Patients usually have a median survival of approximately 14 to 15 months from the diagnosis. Glioblastoma is also known as glioblastoma multiforme. The pathogenesis contributing to the proliferation and metastasis of cancer involves aberrations of multiple signalling pathways through multiple genetic mutations and altered gene expression. The coagulant factors like thrombin and tissue factor play a noteworthy role in cancer invasion. They are produced in the microenvironment of glioma through activation of protease-activated receptors (PARs) which are activated by coagulation proteases. PARs are members of family G-protein-coupled receptors (GPCRs) that are activated by coagulation proteases. These components play a key role in tumour cell angiogenesis, migration, invasion, and interactions with host vascular cells. Further, the release of neurotransmitters is also found to regulate malignancy in gliomas. Exploration of the interplay between malignant neural circuitry with the normal conditions is also decisive in finding effective therapies for these apparently invasive tumours. The present review discusses the molecular classification of gliomas, activation of PARs by coagulation protease, and its role in metastasis of gliomas. Further, the differential involvement of neurotransmitters in the pathogenesis of gliomas has also been discussed. Targeting these molecules may present a potential therapeutic approach for the treatment of gliomas.

Syngeneic Mouse Model of Glioblastoma: Intracranial Implantation of GL261 Cells

Glioblastoma (GBM) is the most aggressive and prevalent primary brain malignancy in adults. Current treatments provide limited benefit, and thus, the median overall survival of GBM patients is only 15 months. GBM progression is highly dependent on its ability to evade immune response, so understanding the mechanisms behind GBM-driven immunosuppression seems crucial for designing more efficient therapies. Animal models of GBM constitute a convenient tool in glioma research, and several different approaches have been already developed to model this disease in vivo, including genetic and xenograft models. Here, we describe a murine syngeneic model of glioma which recapitulates many of the key features of human disease, including complex tumor microenvironment. We present an optimized protocol for stereotactic intracranial implantation of GL261 cells into C57BL/6 mice which results in tumor growth in the striatum. This model has been widely used to get insight into glioma biology, as well as in the studies aiming at the development and validation of new therapeutic approaches.

Preclinical Models and Technologies in Glioblastoma Research: Evolution, Current State, and Future Avenues

Glioblastoma is the most common malignant primary central nervous system tumor and one of the most debilitating cancers. The prognosis of patients with glioblastoma remains poor, and the management of this tumor, both in its primary and recurrent forms, remains suboptimal. Despite the tremendous efforts that are being put forward by the research community to discover novel efficacious therapeutic agents and modalities, no major paradigm shifts have been established in the field in the last decade. However, this does not mirror the abundance of relevant findings and discoveries made in preclinical glioblastoma research. Hence, developing and utilizing appropriate preclinical models that faithfully recapitulate the characteristics and behavior of human glioblastoma is of utmost importance. Herein, we offer a holistic picture of the evolution of preclinical models of glioblastoma. We further elaborate on the commonly used in vitro and vivo models, delving into their development, favorable characteristics, shortcomings, and areas of potential improvement, which aids researchers in designing future experiments and utilizing the most suitable models. Additionally, this review explores progress in the fields of humanized and immunotolerant mouse models, genetically engineered animal models, 3D in vitro models, and microfluidics and highlights promising avenues for the future of preclinical glioblastoma research.

MRI and amino acid PET detection of whole-brain tumor burden

Background

[18F]fluciclovine amino acid PET has shown promise for detecting brain tumor regions undetected on conventional anatomic MRI scans. However, it remains unclear which of these modalities provides a better assessment of the whole brain tumor burden. This study quantifies the performance of [18F]fluciclovine PET and MRI for detecting the whole brain tumor burden.

Methods

Thirteen rats were orthotopically implanted with fluorescently transduced human glioblastoma cells. Rats underwent MRI (T1- and T2-weighted) and [18F]fluciclovine PET. Next brains were excised, optically cleared, and scanned ex vivo with fluorescence imaging. All images were co-registered using a novel landmark-based registration to enable a spatial comparison. The tumor burden identified on the fluorescent images was considered the ground truth for comparison with the in vivo imaging.

Results

Across all cases, the PET sensitivity for detecting tumor burden (median 0.67) was not significantly different than MRI (combined T1+T2-weighted) sensitivity (median 0.61; p=0.85). However, the combined PET+MRI sensitivity (median 0.86) was significantly higher than MRI alone (41% higher; p=0.004) or PET alone (28% higher; p=0.0002). The specificity of combined PET+MRI (median=0.91) was significantly lower compared with MRI alone (6% lower; p=0.004) or PET alone (2% lower; p=0.002).

Conclusion

In these glioblastoma xenografts, [18F]fluciclovine PET did not provide a significant increase in tumor burden detection relative to conventional anatomic MRI. However, a combined PET and MRI assessment did significantly improve detection sensitivity relative to either modality alone, suggesting potential value in a combined assessment for some tumors.

A Cellular Ground Truth to Develop MRI Signatures in Glioma Models by Correlative Light Sheet Microscopy and Atlas-Based Coregistration

Glioblastoma is the most common malignant primary brain tumor with poor overall survival. Magnetic resonance imaging (MRI) is the main imaging modality for glioblastoma but has inherent shortcomings. The molecular and cellular basis of MR signals is incompletely understood. We established a ground truth-based image analysis platform to coregister MRI and light sheet microscopy (LSM) data to each other and to an anatomic reference atlas for quantification of 20 predefined anatomic subregions. Our pipeline also includes a segmentation and quantification approach for single myeloid cells in entire LSM datasets. This method was applied to three preclinical glioma models in male and female mice (GL261, U87MG, and S24), which exhibit different key features of the human glioma. Multiparametric MR data including T2-weighted sequences, diffusion tensor imaging, T2 and T2* relaxometry were acquired. Following tissue clearing, LSM focused on the analysis of tumor cell density, microvasculature, and innate immune cell infiltration. Correlated analysis revealed differences in quantitative MRI metrics between the tumor-bearing and the contralateral hemisphere. LSM identified tumor subregions that differed in their MRI characteristics, indicating tumor heterogeneity. Interestingly, MRI signatures, defined as unique combinations of different MRI parameters, differed greatly between the models. The direct correlation of MRI and LSM allows an in-depth characterization of preclinical glioma and can be used to decipher the structural, cellular, and, likely, molecular basis of tumoral MRI biomarkers. Our approach may be applied in other preclinical brain tumor or neurologic disease models, and the derived MRI signatures could ultimately inform image interpretation in a clinical setting.SIGNIFICANCE STATEMENT We established a histologic ground truth-based approach for MR image analyses and tested this method in three preclinical glioma models exhibiting different features of glioblastoma. Coregistration of light sheet microscopy to MRI allowed for an evaluation of quantitative MRI data in histologically distinct tumor subregions. Coregistration to a mouse brain atlas enabled a regional comparison of MRI parameters with a histologically informed interpretation of the results. Our approach is transferable to other preclinical models of brain tumors and further neurologic disorders. The method can be used to decipher the structural, cellular, and molecular basis of MRI signal characteristics. Ultimately, information derived from such analyses could strengthen the neuroradiological evaluation of glioblastoma as they enhance the interpretation of MRI data.

Radiomics characterization of tissues in an animal brain tumor model imaged using dynamic contrast enhanced (DCE) MRI

Here, we investigate radiomics-based characterization of tumor vascular and microenvironmental properties in an orthotopic rat brain tumor model measured using dynamic-contrast-enhanced (DCE) MRI. Thirty-two immune compromised-RNU rats implanted with human U-251N cancer cells were imaged using DCE-MRI (7Tesla, Dual-Gradient-Echo). The aim was to perform pharmacokinetic analysis using a nested model (NM) selection technique to classify brain regions according to vasculature properties considered as the source of truth. A two-dimensional convolutional-based radiomics analysis was performed on the raw-DCE-MRI of the rat brains to generate dynamic radiomics maps. The raw-DCE-MRI and respective radiomics maps were used to build 28 unsupervised Kohonen self-organizing-maps (K-SOMs). A Silhouette-Coefficient (SC), k-fold Nested-Cross-Validation (k-fold-NCV), and feature engineering analyses were performed on the K-SOMs' feature spaces to quantify the distinction power of radiomics features compared to raw-DCE-MRI for classification of different Nested Models. Results showed that eight radiomics features outperformed respective raw-DCE-MRI in prediction of the three nested models. The average percent difference in SCs between radiomics features and raw-DCE-MRI was: 29.875% ± 12.922%, p < 0.001. This work establishes an important first step toward spatiotemporal characterization of brain regions using radiomics signatures, which is fundamental toward staging of tumors and evaluation of tumor response to different treatments.

GM-CSF and IL-7 fusion cytokine engineered tumor vaccine generates long-term Th-17 memory cells and increases overall survival in aged syngeneic mouse models of glioblastoma

Age-related immune dysfunctions, such as decreased T-cell output, are closely related to pathologies like cancers and lack of vaccine efficacy among the elderly. Engineered fusokine, GIFT-7, a fusion of interleukin 7 (IL-7) and GM-CSF, can reverse aging-related lymphoid organ atrophy. We generated a GIFT-7 fusokine tumor vaccine and employed it in aged syngeneic mouse models of glioblastoma and found that peripheral vaccination with GIFT-7TVax resulted in thymic regeneration and generated durable long-term antitumor immunity specifically in aged mice. Global cytokine analysis showed increased pro-inflammatory cytokines including IL-1β in the vaccinated group that resulted in hyperactivation of dendritic cells. In addition, GIFT-7 vaccination resulted in increased T-cell trafficking to the brain and robust Th-17 long-term effector memory T-cell formation. TCR-seq analysis showed increased productive frequency among detected rearrangements within the vaccinated group. Overall, our data demonstrate that aging immune system can be therapeutically augmented to generate lasting antitumor immunity.

Dynamic contrast enhanced (DCE) MRI estimation of vascular parameters using knowledge-based adaptive models

We introduce and validate four adaptive models (AMs) to perform a physiologically based Nested-Model-Selection (NMS) estimation of such microvascular parameters as forward volumetric transfer constant, Ktrans, plasma volume fraction, vp, and extravascular, extracellular space, ve, directly from Dynamic Contrast-Enhanced (DCE) MRI raw information without the need for an Arterial-Input Function (AIF). In sixty-six immune-compromised-RNU rats implanted with human U-251 cancer cells, DCE-MRI studies estimated pharmacokinetic (PK) parameters using a group-averaged radiological AIF and an extended Patlak-based NMS paradigm. One-hundred-ninety features extracted from raw DCE-MRI information were used to construct and validate (nested-cross-validation, NCV) four AMs for estimation of model-based regions and their three PK parameters. An NMS-based a priori knowledge was used to fine-tune the AMs to improve their performance. Compared to the conventional analysis, AMs produced stable maps of vascular parameters and nested-model regions less impacted by AIF-dispersion. The performance (Correlation coefficient and Adjusted R-squared for NCV test cohorts) of the AMs were: 0.914/0.834, 0.825/0.720, 0.938/0.880, and 0.890/0.792 for predictions of nested model regions, vp, Ktrans, and ve, respectively. This study demonstrates an application of AMs that quickens and improves DCE-MRI based quantification of microvasculature properties of tumors and normal tissues relative to conventional approaches.

The first endovascular rat glioma model for pre-clinical evaluation of intra-arterial therapeutics

BACKGROUND

Several translational animal models have been described assessing intra-arterial (IA) treatments for malignant gliomas. We describe the first endovascular animal model that allows testing of IA drug delivery as a first-line treatment, which is difficult to do in actual patients. We report a unique protocol for vascular access and IA delivery in the rat model that, unlike prior reports, does not require direct puncture and opening of proximal cerebrovasculature which carries risk of ischemia in the animal brain post-delivery.

METHODS

Wistar rats underwent left femoral artery catherization with a Balt Magic 1.2F catheter or Marathon Flow directed 1.5F Microcatheter with an Asahi Chikai 0.008 micro-guidewire which was navigated to the left internal carotid artery under x-ray. 25% mannitol was administered to test blood brain barrier breakdown (BBBB). Additional rats were implanted with C6 glioma cells in the left frontal lobe. C6 Glioma-Implanted Rats (C6GRs) were monitored for overall survival and tumor growth. Tumor volumes from MRI images were calculated utilizing 3D slicer. Additional rats underwent femoral artery catheterization with Bevacizumab, carboplatin, or irinotecan injected into the left internal carotid artery to test feasibility and safety.

RESULTS

A successful endovascular access and BBBB protocol was established. BBBB was confirmed with positive Evans blue staining. 10 rats were successfully implanted with C6 gliomas with confirmed growths on MRI. Overall survival was 19.75 ± 2.21 days. 5 rats were utilized for the development of our femoral catheterization protocol and BBBB testing. With regards to IA chemotherapy dosage testing, control rats tolerated targeted 10 mg/kg of bevascizumab, 2.4 mg/kg of carboplatin, and 15 mg/kg of irinotecan IA ICA injections without any complications.

CONCLUSIONS

We present the first endovascular IA rat glioma model that allows selective catheterization of the intracranial vasculature and assessment of IA therapies for gliomas without need for access and sacrifice of proximal cerebrovasculature.

Functional Graphene for Peritumoral Brain Microenvironment Modulation Therapy in Glioblastoma

Peritumoral brain invasion is the main target to cure glioblastoma. Chemoradiotherapy and targeted therapies fail to combat peritumoral relapse. Brain inaccessibility and tumor heterogeneity explain this failure, combined with overlooking the peritumor microenvironment. Reduce graphene oxide (rGO) provides a unique opportunity to modulate the local brain microenvironment. Multimodal graphene impacts are reported on glioblastoma cells in vitro but fail when translated in vivo because of low diffusion. This issue is solved by developing a new rGO formulation involving ultramixing during the functionalization with polyethyleneimine (PEI) leading to the formation of highly water-stable rGO-PEI. Wide mice brain diffusion and biocompatibility are demonstrated. Using an invasive GL261 model, an anti-invasive effect is observed. A major unexpected modification of the peritumoral area is also observed with the neutralization of gliosis. In vitro, mechanistic investigations are performed using primary astrocytes and cytokine array. The result suggests that direct contact of rGO-PEI_UT neutralizes astrogliosis, decreasing several proinflammatory cytokines that would explain a bystander tumor anti-invasive effect. rGO also significantly downregulates several proinvasive/protumoral cytokines at the tumor cell level. The results open the way to a new microenvironment anti-invasive nanotherapy using a new graphene nanomaterial that is optimized for in vivo brain delivery.

All-Nontoxic Fluorescent Probe for Biothiols and Its Clinical Applications for Real-Time Glioblastoma Visualization

Fluorescence-guided surgery (FSG) is a surgical method to selectively visualize the tumor site using fluorescent materials with instrumental setups in the operation rooms. It has been widely used in the surgery of brain tumors, such as glioblastoma (GBM), which is difficult to distinguish from normal tissue. Although FSG is crucial for GBM surgery, the commercially available fluorescent materials for FSG have shown serious adverse effects. To satisfy the clinical demand, we recently reported reaction-based fluorescent probes based on a 4-chloro-7-nitrobenzofurazan (NBD) fluorophore that can detect cysteine (Cys) and homocysteine (Hcy), a biomarker of GBM, and their applications for the GBM diagnosis and FSG. However, our probes have cellular toxicity issues arising from the leaving group (LG) that is generated after the reaction of the fluorescent probe and the analytes. In this study, we disclosed a nontoxic fluorescent probe for sensing biothiols and their clinical applications for real-time human glioblastoma visualization. Systematic toxicity analysis of several LGs was conducted on several cell lines. Among the LGs, 2-hydroxy-pyridine showed negligible toxicity, and its fluorescent probe derivative (named NPO-o-Pyr) showed high specificity and sensitivity (LOD: 0.071 ppm for Cys; 0.189 ppm for Hcy), a fast response time (<5 min) to Cys and Hcy, and high biocompatibility. In addition, NPO-o-Pyr can significantly detect the GBM site both in actual clinical samples as well as in the GBM-xenografted mouse model. We are confident that NPO-o-Pyr will become a new substitute in FSG due to its capability to overcome the limitations of the current fluorescent probes.

Mismatch between Bioluminescence Imaging (BLI) and MRI When Evaluating Glioblastoma Growth: Lessons from a Study Where BLI Suggested "Regression" while MRI Showed "Progression"

Orthotopic glioblastoma xenografts are paramount for evaluating the effect of innovative anti-cancer treatments. In longitudinal studies, tumor growth (or regression) of glioblastoma can only be monitored by noninvasive imaging. For this purpose, bioluminescence imaging (BLI) has gained popularity because of its low cost and easy access. In the context of the development of new nanomedicines for treating glioblastoma, we were using luciferase-expressing GL261 cell lines. Incidentally, using BLI in a specific GL261 glioblastoma model with cells expressing both luciferase and the green fluorescent protein (GL261-luc-GFP), we observed an apparent spontaneous regression. By contrast, the magnetic resonance imaging (MRI) analysis revealed that the tumors were actually growing over time. For other models (GL261 expressing only luciferase and U87 expressing both luciferase and GFP), data from BLI and MRI correlated well. We found that the divergence in results coming from different imaging modalities was not due to the tumor localization nor the penetration depth of light but was rather linked to the instability in luciferase expression in the viral construct used for the GL261-luc-GFP model. In conclusion, the use of multi-modality imaging prevents possible errors in tumor growth evaluation, and checking the stability of luciferase expression is mandatory when using BLI as the sole imaging modality.

Locomotion Outcome Improvement in Mice with Glioblastoma Multiforme after Treatment with Anastrozole

Glioblastoma Multiforme (GBM) is a tumor that infiltrates several brain structures. GBM is associated with abnormal motor activities resulting in impaired mobility, producing a loss of functional motor independence. We used a GBM xenograft implanted in the striatum to analyze the changes in Y (vertical) and X (horizontal) axis displacement of the metatarsus, ankle, and knee. We analyzed the steps dissimilarity factor between control and GBM mice with and without anastrozole. The body weight of the untreated animals decreased compared to treated mice. Anastrozole reduced the malignant cells and decreased GPR30 and ERα receptor expression. In addition, we observed a partial recovery in metatarsus and knee joint displacement (dissimilarity factor). The vertical axis displacement of the GBM+anastrozole group showed a difference in the right metatarsus, right knee, and left ankle compared to the GBM group. In the horizontal axis displacement of the right metatarsus, ankle, and knee, the GBM+anastrozole group exhibited a difference at the last third of the step cycle compared to the GBM group. Thus, anastrozole partially modified joint displacement. The dissimilarity factor and the vertical and horizontal displacements study will be of interest in GBM patients with locomotion alterations. Hindlimb displacement and gait locomotion analysis could be a valuable methodological tool in experimental and clinical studies to help diagnose locomotive deficits related to GBM.

From kitchen to clinic: Pharmacotherapeutic potential of common spices in Indian cooking in age-related neurological disorders

Aging is described as an advanced time-related collection of changes that may negatively affect with the risk of several diseases or death. Aging is a main factor of several age-related neurological disorders, including neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease, and dementia), stroke, neuroinflammation, neurotoxicity, brain tumors, oxidative stress, and reactive oxygen species (ROS). Currently available medications for age-related neurological disorders may lead to several side effects, such as headache, diarrhea, nausea, gastrointestinal (GI) diseases, dyskinesia, and hallucinosis. These days, studies on plant efficacy in traditional medicine are being conducted because herbal medicine is affordable, safe, and culturally acceptable and easily accessible. The Indian traditional medicine system called Ayurveda uses several herbs and medicinal plants to treat various disorders including neurological disorders. This review aims to summarize the data on the neuroprotective potential of the following common Indian spices widely used in Ayurveda: cumin (Cuminum cyminum (L.), Apiaceae), black cumin (Nigella sativa (L.), Ranunculaceae), black pepper (Piper nigrum (L.), Piperaceae), curry leaf tree (Murraya koenigii (L.), Spreng Rutaceae), fenugreek (Trigonella foenum-graecum (L.), Fabaceae), fennel (Foeniculum vulgare Mill, Apiaceae), cardamom (Elettaria cardamomum (L.) Maton, Zingiberaceae), cloves (Syzygium aromaticum (L.) Merr. & L.M.Perry, Myrtaceae), and coriander (Coriandrum sativum (L.), Apiaceae) in age-related neurological disorders.

Potential of cytochrome P450, a family of xenobiotic metabolizing enzymes, in cancer therapy

SIGNIFICANCE

Targeted cancer therapy with minimal off-target consequences has shown promise for some cancer types. Although cytochrome P450 (CYP) consists of 18 families, CYP1-4 families play key role in metabolizing xenobiotics and cancer drugs. This eventually affects the process of carcinogenesis, treatment outcome, and cancer drug resistance. Differential overexpression of CYPs in transformed cells, together with phenotypic alterations in tumors, presents a potential for therapeutic intervention.

RECENT ADVANCES

Recent advances in molecular tools and information technology have helped utilize CYPs as cancer targets. The precise expression in various tumors, X-ray crystal structures, improved understanding of the structure-activity relationship, and new approaches in the development of prodrugs have supported the ongoing efforts to develop CYPs-based drugs with a better therapeutic index.

CRITICAL ISSUES

Narrow therapeutic index, off-target effects, drug resistance, and tumor heterogeneity limit the benefits of CYP-based conventional cancer therapies. In this review, we address the CYP1-4 families as druggable targets in cancer. An emphasis is given to the CYP expression, function, and the possible mechanisms that drive expression and activity in normal and transformed tissues. The strategies that inhibit or activate CYPs for therapeutic benefits are also discussed.

FUTURE DIRECTIONS

Efforts are needed to develop more selective tools that will help comprehend molecular and metabolic alterations in tumor tissues with biological end-points in relation to CYPs. This will eventually translate to developing more specific CYP inhibitors/inducers.

Physical Training Protects Against Brain Toxicity in Mice Exposed to an Experimental Model of Glioblastoma

Glioma 261 (Gl261) cell-mediated neurotoxicity has been reported in previous studies examining glioblastoma (GBM), and the effects of physical exercise (PE) on this neurotoxicity have been poorly investigated. This study aimed to evaluate the effects of a PE program in animals with experimental GBM. Male C57BL/6J mice were randomized into sham or GBM groups and subjected to a PE program for four weeks. Gl261 cells were administered into the intraventricular region at 48 h after the last exercise session. Body weight, water and feed consumption, and behavior were all evaluated for 21 days followed by euthanasia. The right parietal lobe was removed for the analysis of glial fibrillary acidic protein (GFAP), epidermal growth factor receptor (EGFR), vimentin, C-myc, nuclear factor kappa B (NF-κB), tumor necrosis factor-alpha (TNF-α), interleukin 1 beta (IL-1β), interleukin 6 (IL-6), hydrogen peroxide, the glutathione system, and oxidative damage to proteins. The results revealed changes in the behavioral patterns of the trained animals, and no anatomopathological changes were observed in response to PE training. In contrast, animals with GBM subjected to PE exhibited lower immunoexpression of c-MYC, vimentin, and GFAP. Although experimental GBM altered the redox profile and inflammatory mediators, no significant alterations were observed after PE. In conclusion, our data provide consistent evidence of the relationship between PE and the improvement of tumorigenic parameters against the neurotoxicity of GL261 cells.

VCAM-1-targeted MRI Improves Detection of the Tumor-brain Interface

PURPOSE

Despite optimal local therapy, tumor cell invasion into normal brain parenchyma frequently results in recurrence in patients with solid tumors. The aim of this study was to determine whether microvascular inflammation can be targeted to better delineate the tumor-brain interface through vascular cell adhesion molecule-1 (VCAM-1)-targeted MRI.

EXPERIMENTAL DESIGN

Intracerebral xenograft rat models of MDA231Br-GFP (breast cancer) brain metastasis and U87MG (glioblastoma) were used to histologically examine the tumor-brain interface and to test the efficacy of VCAM-1-targeted MRI in detecting this region. Human biopsy samples of the brain metastasis and glioblastoma margins were examined for endothelial VCAM-1 expression.

RESULTS

The interface between tumor and surrounding normal brain tissue exhibited elevated endothelial VCAM-1 expression and increased microvessel density. Tumor proliferation and stemness markers were also significantly upregulated at the tumor rim in the brain metastasis model. T2*-weighted MRI, following intravenous administration of VCAM-MPIO, highlighted the tumor-brain interface of both tumor models more extensively than gadolinium-DTPA-enhanced T1-weighted MRI. Sites of VCAM-MPIO binding, evident as hypointense signals on MR images, correlated spatially with endothelial VCAM-1 upregulation and bound VCAM-MPIO beads detected histologically. These findings were further validated in an orthotopic medulloblastoma model. Finally, the tumor-brain interface in human brain metastasis and glioblastoma samples was similarly characterized by microvascular inflammation, extending beyond the region detectable using conventional MRI.

CONCLUSIONS

This work illustrates the potential of VCAM-1-targeted MRI for improved delineation of the tumor-brain interface in both primary and secondary brain tumors.

Homogeneity of antibody-drug conjugates critically impacts the therapeutic efficacy in brain tumors

Glioblastoma multiforme (GBM) is the most aggressive and fatal disease of all brain tumor types. Most therapies rarely provide clinically meaningful outcomes in the treatment of GBM. Although antibody-drug conjugates (ADCs) are promising anticancer drugs, no ADCs have been clinically successful for GBM, primarily because of poor blood-brain barrier (BBB) penetration. Here, we report that ADC homogeneity and payload loading rate are critical parameters contributing to this discrepancy. Although both homogeneous and heterogeneous conjugates exhibit comparable in vitro potency and pharmacokinetic profiles, the former shows enhanced payload delivery to brain tumors. Our homogeneous ADCs provide improved antitumor effects and survival benefits in orthotopic brain tumor models. We also demonstrate that overly drug-loaded species in heterogeneous conjugates are particularly poor at crossing the BBB, leading to deteriorated overall brain tumor targeting. Our findings indicate the importance of homogeneous conjugation with optimal payload loading in generating effective ADCs for intractable brain tumors.

Most therapies rarely provide clinically meaningful improvements in glioblastoma multiforme (GBM) treatment. Anami et al. report that intravenous administration of homogeneous antibody-drug conjugates (ADCs) efficiently delivers payloads to brain tumors, leading to substantially improved tumor growth suppression. Their findings provide rational ADC design for effectively treating intractable brain tumors, including GBM.

LDH-A—Modulation and the Variability of LDH Isoenzyme Profiles in Murine Gliomas: A Link with Metabolic and Growth Responses

Three murine glioma cell lines (GL261, CT2A, and ALTS1C1) were modified to downregulate the expression of the murine LDH-A gene using shRNA, and compared to shRNA scrambled control (NC) cell lines. Differences in the expression of LDH-A and LDH-B mRNA, protein and enzymatic activity, as well as their LDH isoenzyme profiles, were observed in the six cell lines, and confirmed successful LDH-A KD. LDH-A KD (knock-down) resulted in metabolic changes in cells with a reduction in glycolysis (GlycoPER) and an increase in basal respiratory rate (mitoOCR). GL261 cells had a more limited ATP production capacity compared to CT2A and ALTS1C1 cells. An analysis of mRNA expression data indicated that: (i) GL261 LDH-A KD cells may have an improved ability to metabolize lactate into the TCA cycle; and (ii) that GL261 LDH-A KD cells can upregulate lipid metabolism/fatty acid oxidation pathways, whereas the other glioma cell lines do not have this capacity. These two observations suggest that GL261 LDH-A KD cells can develop/activate alternative metabolic pathways for enhanced survival in a nutrient-limited environment, and that specific nutrient limitations have a variable impact on tumor cell metabolism and proliferation. The phenotypic effects of LDH-A KD were compared to those in control (NC) cells and tumors. LDH-A KD prolonged the doubling time of GL261 cells in culture and prevented the formation of subcutaneous flank tumors in immune-competent C57BL/6 mice, whereas GL261 NC tumors had a prolonged growth delay in C57BL/6 mice. In nude mice, both LDH-A KD and NC GL261 tumors grew rapidly (more rapidly than GL261 NC tumors in C57BL/6 mice), demonstrating the impact of an intact immune system on GL261 tumor growth. No differences between NC and KD cell proliferation (in vitro) or tumor growth in C57BL/6 mice (doubling time) were observed for CT2A and ALTS1C1 cells and tumors, despite the small changes to their LDH isoenzyme profiles. These results suggest that GL261 glioma cells (but not CT2A and ALTS1C1 cells) are pre-programmed to have the capacity for activating different metabolic pathways with higher TCA cycle activity, and that this capacity is enhanced by LDH-A depletion. We observed that the combined impact of LDH-A depletion and the immune system had a significant impact on the growth of subcutaneous-located GL261 tumors.

Endothelial EphrinB2 Regulates Sunitinib Therapy Response in Murine Glioma

Vascular guidance is critical in developmental vasculogenesis and pathological angiogenesis. Brain tumors are strongly vascularized, and antiangiogenic therapy was anticipated to exhibit a strong anti-tumor effect in this tumor type. However, vascular endothelial growth factor A (VEGFA) specific inhibition had no significant impact in clinical practice of gliomas. More research is needed to understand the failure of this therapeutic approach. EphrinB2 has been found to directly interact with vascular endothelial growth factor receptor 2 (VEGFR2) and regulate its activity. Here we analyzed the expression of ephrinB2 and EphB4 in human glioma, we observed vascular localization of ephrinB2 in physiology and pathology and found a significant survival reduction in patients with elevated ephrinB2 tumor expression. Induced endothelial specific depletion of ephrinB2 in the adult mouse (efnb2i∆EC) had no effect on the quiescent vascular system of the brain. However, we found glioma growth and perfusion altered in efnb2i∆EC animals similar to the effects observed with antiangiogenic therapy. No additional anti-tumor effect was observed in efnb2i∆EC animals treated with antiangiogenic therapy. Our data indicate that ephrinB2 and VEGFR2 converge on the same pathway and intervention with either molecule results in a reduction in angiogenesis.

Brain tumor classification of virtual NMR voxels based on realistic blood vessel-induced spin dephasing using support vector machines

Remodeling of tissue microvasculature commonly promotes neoplastic growth; however, there is no imaging modality in oncology yet that noninvasively quantifies microvascular changes in clinical routine. Although blood capillaries cannot be resolved in typical magnetic resonance imaging (MRI) measurements, their geometry and distribution influence the integral nuclear magnetic resonance (NMR) signal from each macroscopic MRI voxel. We have numerically simulated the expected transverse relaxation in NMR voxels with different dimensions based on the realistic microvasculature in healthy and tumor-bearing mouse brains (U87 and GL261 glioblastoma). The 3D capillary structure in entire, undissected brains was acquired using light sheet fluorescence microscopy to produce large datasets of the highly resolved cerebrovasculature. Using this data, we trained support vector machines to classify virtual NMR voxels with different dimensions based on the simulated spin dephasing accountable to field inhomogeneities caused by the underlying vasculature. In prediction tests with previously blinded virtual voxels from healthy brain tissue and GL261 tumors, stable classification accuracies above 95% were reached. Our results indicate that high classification accuracies can be stably attained with achievable training set sizes and that larger MRI voxels facilitated increasingly successful classifications, even with small training datasets. We were able to prove that, theoretically, the transverse relaxation process can be harnessed to learn endogenous contrasts for single voxel tissue type classifications on tailored MRI acquisitions. If translatable to experimental MRI, this may augment diagnostic imaging in oncology with automated voxel-by-voxel signal interpretation to detect vascular pathologies.

Clinically relevant orthotopic xenograft models of patient-derived glioblastoma in zebrafish

An accurate prediction of the intracranial infiltration tendency and drug response of individual glioblastoma (GBM) cells is essential for personalized prognosis and treatment for this disease. However, the clinical utility of mouse patient-derived orthotopic xenograft (PDOX) models remains limited given current technical constraints, including difficulty in generating sufficient sample numbers from small tissue samples and a long latency period for results. To overcome these issues, we established zebrafish GBM xenografts of diverse origin, which can tolerate intracranial engraftment and maintain their unique histological features. Subsequent single-cell RNA-sequencing (scRNA-seq) analysis confirmed significant transcriptional identity to that of invading GBM microtumors observed in the proportionally larger brains of model animals and humans. Endothelial scRNA-seq confirmed that the zebrafish blood–brain barrier is homologous to the mammalian blood–brain barrier. Finally, we established a rapid and efficient zebrafish PDOX (zPDOX) model, which can predict long-term outcomes of GBM patients within 20 days. The zPDOX model provides a novel avenue for precision medicine of GBM, especially for the evaluation of intracranial infiltration tendency and prediction of individual drug sensitivity.

Editor's choice: We established zebrafish glioblastoma (GBM) xenograft models that can be used to perform genetic and biological analysis of GBMs, identify blood–brain barrier-penetrating drugs and predict clinical sensitivity to temozolomide in GBM patients.

Establishing Imaging Biomarkers of Host Immune System Efficacy during Glioblastoma Therapy Response: Challenges, Obstacles and Future Perspectives

This hypothesis proposal addresses three major questions: (1) Why do we need imaging biomarkers for assessing the efficacy of immune system participation in glioblastoma therapy response? (2) Why are they not available yet? and (3) How can we produce them? We summarize the literature data supporting the claim that the immune system is behind the efficacy of most successful glioblastoma therapies but, unfortunately, there are no current short-term imaging biomarkers of its activity. We also discuss how using an immunocompetent murine model of glioblastoma, allowing the cure of mice and the generation of immune memory, provides a suitable framework for glioblastoma therapy response biomarker studies. Both magnetic resonance imaging and magnetic resonance-based metabolomic data (i.e., magnetic resonance spectroscopic imaging) can provide non-invasive assessments of such a system. A predictor based in nosological images, generated from magnetic resonance spectroscopic imaging analyses and their oscillatory patterns, should be translational to clinics. We also review hurdles that may explain why such an oscillatory biomarker was not reported in previous imaging glioblastoma work. Single shot explorations that neglect short-term oscillatory behavior derived from immune system attack on tumors may mislead actual response extent detection. Finally, we consider improvements required to properly predict immune system-mediated early response (1–2 weeks) to therapy. The sensible use of improved biomarkers may enable translatable evidence-based therapeutic protocols, with the possibility of extending preclinical results to human patients.

LPPR5 Expression in Glioma Affects Growth, Vascular Architecture, and Sunitinib Resistance

Despite intensive research, glioblastoma remains almost invariably fatal. Various promising drugs targeting specific aspects of glioma biology, in addition to or as an alternative to antiproliferative chemotherapy, were not successful in larger clinical trials. Further insights into the biology of glioma and the mechanisms behind the evasive-adaptive response to targeted therapies is needed to help identify new therapeutic targets, prognostics, or predictive biomarkers. As a modulator of the canonically oncogenic Rho-GTPase pathway, Lipid phosphate phosphatase-related protein type 5 (LPPR5) is pivotal in influencing growth, angiogenesis, and therapeutic resistance. We used a GL261 murine orthotopic allograft glioma model to quantify the tumor growth and to obtain tissue for histological and molecular analysis. Epicortical intravital epi-illumination fluorescence video microscopy of the tumor cell spheroids was used to characterize the neovascular architecture and hemodynamics. GL261-glioma growth was delayed and decelerated after LPPR5 overexpression (LPPR5^OE). We observed increased tumor cell apoptosis and decreased expression and secretion of vascular endothelial growth factor A in LPPR5^OE glioma. Hence, an altered micro-angioarchitecture consisting of dysfunctional small blood vessels was discovered in the LPPR5^OE tumors. Sunitinib therapy eliminated these vessels but had no effect on tumor growth or apoptosis. In general, LPPR5 overexpression generated a more benign, proapoptotic glioma phenotype with delayed growth and a dysfunctional vascular architecture.

Transferrin-modified nanoparticles for targeted delivery of Asiatic acid to glioblastoma cells

AIMS

Glioblastoma (GBM) is the most common and deadliest type of brain cancer, and the current therapeutic options are not curative, imposing the need for novel strategies. Asiatic acid (AA) is a natural compound and has been explored due to its anti-glioma activity and lower toxicity to healthy tissues compared with conventional chemotherapeutic agents. However, its poor water-solubility is an obstacle for clinical application. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) were proposed in this work for Asiatic acid (AA) delivery.

MAIN METHODS

A central composite design was implemented to optimize the NPs, and their surface was further modified with transferrin (Tf), for targeted delivery to GBM cells. The anti-glioma activity of the NPs was studied in vitro using human GBM cells and immortalized human astrocytes.

KEY FINDINGS

The NPs exhibited a mean size smaller than 200 nm, with low polydispersity and negative zeta potential, indicating their suitability for brain tumor delivery. The NPs also exhibited high encapsulation efficiency and maintained a slow and controlled release of AA for 20 days. In vitro cell studies showed that NPs were able to maintain the anti-glioma activity of the natural compound and that the surface modification with Tf molecules was able to increase the cellular uptake in GBM cells, enhancing their selectivity and decreasing toxicity in healthy cells.

SIGNIFICANCE

Overall, this work provided guidance for designing brain-targeting delivery systems of natural compounds.

Nanomedicine for brain cancer

CNS tumors remain among the deadliest forms of cancer, resisting conventional and new treatment approaches, with mortality rates staying practically unchanged over the past 30 years. One of the primary hurdles for treating these cancers is delivering drugs to the brain tumor site in therapeutic concentration, evading the blood-brain (tumor) barrier (BBB/BBTB). Supramolecular nanomedicines (NMs) are increasingly demonstrating noteworthy prospects for addressing these challenges utilizing their unique characteristics, such as improving the bioavailability of the payloadsviacontrolled pharmacokinetics and pharmacodynamics, BBB/BBTB crossing functions, superior distribution in the brain tumor site, and tumor-specific drug activation profiles. Here, we review NM-based brain tumor targeting approaches to demonstrate their applicability and translation potential from different perspectives. To this end, we provide a general overview of brain tumor and their treatments, the incidence of the BBB and BBTB, and their role on NM targeting, as well as the potential of NMs for promoting superior therapeutic effects. Additionally, we discuss critical issues of NMs and their clinical trials, aiming to bolster the potential clinical applications of NMs in treating these life-threatening diseases.

Imaging Glioblastoma With 18F-Fluciclovine Amino Acid Positron Emission Tomography

Introduction

Conventional methods of imaging brain tumors fail to assess metabolically active tumor regions, which limits their capabilities for tumor detection, localization, and response assessment. Positron emission tomography (PET) with 18F-fluciclovine (fluciclovine) provides regional assessment of amino acid uptake in tumors that could overcome some of the limitations of conventional imaging. However, the biological basis of enhanced fluciclovine uptake is insufficiently characterized in brain tumors, which confounds clinical interpretation and application. This study sought to address this gap by correlating multiple biologic quantities with fluciclovine PET uptake across a range of human glioblastoma xenograft models.

Methods

Thirty-one rats underwent orthotopic implantations with one of five different human glioblastoma cell lines. After tumors were established, fluciclovine PET and magnetic resonance imaging (MRI) scans were performed. The fluciclovine tumor-to-normal-brain (TN) uptake ratio was used to quantify fluciclovine uptake. MRI scans were used to assess tumor volume and gadolinium enhancement status. Histologic assessments quantified tumor cell proliferation, tumor cell density, and tumor cell amino acid transporters (LAT1 and ASCT2). Multivariate linear regression models related fluciclovine uptake with the other measured quantities.

Results

Within the multivariate regression, the fluciclovine TN uptake ratio (measured 15 to 35 minutes after fluciclovine injection) was most strongly associated with tumor ASCT2 levels (β=0.64; P=0.001). The fluciclovine TN uptake ratio was also significantly associated with tumor volume (β=0.45; P=0.001) and tumor enhancement status (β=0.40; P=0.01). Tumor cell proliferation, tumor cell density, and LAT1 levels were not significantly associated with fluciclovine uptake in any of the multivariate models. In general, both enhancing and non-enhancing tumors could be visualized on fluciclovine PET images, with the median TN uptake ratio across the five tumor lines being 2.4 (range 1.1 to 8.9).

Conclusions

Increased fluciclovine PET uptake was associated with increased levels of the amino acid transporter ASCT2, suggesting fluciclovine PET may be useful for assessing brain tumor amino acid metabolism. Fluciclovine PET uptake was elevated in both enhancing and non-enhancing tumors but the degree of uptake was greater in larger tumors and tumors with enhancement, indicating these variables could confound fluciclovine metabolic measurements if not accounted for.

Preclinical models of glioblastoma: limitations of current models and the promise of new developments

Glioblastoma (GBM) is the most common and aggressive primary brain tumour, yet little progress has been made towards providing better treatment options for patients diagnosed with this devastating condition over the last few decades. The complex nature of the disease, heterogeneity, highly invasive potential of GBM tumours and until recently, reduced investment in research funding compared with other cancer types, are contributing factors to few advancements in disease management. Survival rates remain low with less than 5% of patients surviving 5 years. Another important contributing factor is the use of preclinical models that fail to fully recapitulate GBM pathophysiology, preventing efficient translation from the lab into successful therapies in the clinic. This review critically evaluates current preclinical GBM models, highlighting advantages and disadvantages of using such models, and outlines several emerging techniques in GBM modelling using animal-free approaches. These novel approaches to a highly complex disease such as GBM show evidence of a more truthful recapitulation of GBM pathobiology with high reproducibility. The resulting advancements in this field will offer new biological insights into GBM and its aetiology with potential to contribute towards the development of much needed improved treatments for GBM in future.

Rationally designed drug delivery systems for the local treatment of resected glioblastoma

Glioblastoma (GBM) is a particularly aggressive brain cancer associated with high recurrence and poor prognosis. The standard of care, surgical resection followed by concomitant radio- and chemotherapy, leads to low survival rates. The local delivery of active agents within the tumor resection cavity has emerged as an attractive means to initiate oncological treatment immediately post-surgery. This complementary approach bypasses the blood-brain barrier, increases the local concentration at the tumor site while reducing or avoiding systemic side effects. This review will provide a global overview on the local treatment for GBM with an emphasis on the lessons learned from past clinical trials. The main parameters to be considered to rationally design fit-of-purpose biomaterials and develop drug delivery systems for local administration in the GBM resection cavity to prevent the tumor recurrence will be described. The intracavitary local treatment of GBM should i) use materials that facilitate translation to the clinic; ii) be characterized by easy GMP effective scaling up and easy-handling application by the neurosurgeons; iii) be adaptable to fill the tumor-resected niche, mold to the resection cavity or adhere to the exposed brain parenchyma; iv) be biocompatible and possess mechanical properties compatible with the brain; v) deliver a therapeutic dose of rationally-designed or repurposed drug compound(s) into the GBM infiltrative margin. Proof of concept with high translational potential will be provided. Finally, future perspectives to facilitate the clinical translation of the local perisurgical treatment of GBM will be discussed.

Mouse models of glioblastoma for the evaluation of novel therapeutic strategies

Glioblastoma (GBM) is an incurable brain tumor with a median survival of approximately 15 months despite an aggressive standard of care that includes surgery, chemotherapy, and ionizing radiation. Mouse models have advanced our understanding of GBM biology and the development of novel therapeutic strategies for GBM patients. However, model selection is crucial when testing developmental therapeutics, and each mouse model of GBM has unique advantages and disadvantages that can influence the validity and translatability of experimental results. To shed light on this process, we discuss the strengths and limitations of 3 types of mouse GBM models in this review: syngeneic models, genetically engineered mouse models, and xenograft models, including traditional xenograft cell lines and patient-derived xenograft models.

A perspective on the radiopharmaceutical requirements for imaging and therapy of glioblastoma

Despite numerous clinical trials and pre-clinical developments, the treatment of glioblastoma (GB) remains a challenge. The current survival rate of GB averages one year, even with an optimal standard of care. However, the future promises efficient patient-tailored treatments, including targeted radionuclide therapy (TRT). Advances in radiopharmaceutical development have unlocked the possibility to assess disease at the molecular level allowing individual diagnosis. This leads to the possibility of choosing a tailored, targeted approach for therapeutic modalities. Therapeutic modalities based on radiopharmaceuticals are an exciting development with great potential to promote a personalised approach to medicine. However, an effective targeted radionuclide therapy (TRT) for the treatment of GB entails caveats and requisites. This review provides an overview of existing nuclear imaging and TRT strategies for GB. A critical discussion of the optimal characteristics for new GB targeting therapeutic radiopharmaceuticals and clinical indications are provided. Considerations for target selection are discussed, i.e. specific presence of the target, expression level and pharmacological access to the target, with particular attention to blood-brain barrier crossing. An overview of the most promising radionuclides is given along with a validation of the relevant radiopharmaceuticals and theranostic agents (based on small molecules, peptides and monoclonal antibodies). Moreover, toxicity issues and safety pharmacology aspects will be presented, both in general and for the brain in particular.

Allosteric Antagonist Modulation of TRPV2 by Piperlongumine Impairs Glioblastoma Progression

The use of computational tools to identify biological targets of natural products with anticancer properties and unknown modes of action is gaining momentum. We employed self-organizing maps to deconvolute the phenotypic effects of piperlongumine (PL) and establish a link to modulation of the human transient receptor potential vanilloid 2 (hTRPV2) channel. The structure of the PL-bound full-length rat TRPV2 channel was determined by cryo-EM. PL binds to a transient allosteric pocket responsible for a new mode of anticancer activity against glioblastoma (GBM) in which hTRPV2 is overexpressed. Calcium imaging experiments revealed the importance of Arg539 and Thr522 residues on the antagonistic effect of PL and calcium influx modulation of the TRPV2 channel. Downregulation of hTRPV2 reduces sensitivity to PL and decreases ROS production. Analysis of GBM patient samples associates hTRPV2 overexpression with tumor grade, disease progression, and poor prognosis. Extensive tumor abrogation and long term survival was achieved in two murine models of orthotopic GBM by formulating PL in an implantable scaffold/hydrogel for sustained local therapy. Furthermore, in primary tumor samples derived from GBM patients, we observed a selective reduction of malignant cells in response to PL ex vivo. Our results establish a broadly applicable strategy, leveraging data-motivated research hypotheses for the discovery of novel means tackling cancer.

Anti-PD-1 checkpoint blockade monotherapy in the orthotopic GL261 glioma model: the devil is in the detail

The GL261 cell line, syngeneic on the C57BL/6 background, has, since its establishment half a century ago in 1970, become the most commonly used immunocompetent murine model of glioblastoma. As immunotherapy has entered the mainstream of clinical discourse in the past decade, this model has proved its worth as a formidable opponent against various immunotherapeutic combinations. Although advances in surgical, radiological, and chemotherapeutic interventions have extended mean glioblastoma patient survival by several months, 5-year survival postdiagnosis remains below 5%. Immunotherapeutic interventions, such as the ones explored in the murine GL261 model, may prove beneficial for patients with glioblastoma. However, even common immunotherapeutic interventions in the GL261 model still have unclear efficacy, with wildly discrepant conclusions being made in the literature regarding this topic. Here, we focus on anti-PD-1 checkpoint blockade monotherapy as an example of this pattern. We contend that a fine-grained analysis of how biological variables (age, sex, tumor location, etc.) predict treatment responsiveness in this preclinical model will better enable researchers to identify glioblastoma patients most likely to benefit from checkpoint blockade immunotherapy moving forward.

Terbium-Based AGuIX-Design Nanoparticle to Mediate X-ray-Induced Photodynamic Therapy

X-ray-induced photodynamic therapy is based on the energy transfer from a nanoscintillator to a photosensitizer molecule, whose activation leads to singlet oxygen and radical species generation, triggering cancer cells to cell death. Herein, we synthesized ultra-small nanoparticle chelated with Terbium (Tb) as a nanoscintillator and 5-(4-carboxyphenyl succinimide ester)-10,15,20-triphenyl porphyrin (P1) as a photosensitizer (AGuIX@Tb-P1). The synthesis was based on the AGuIX@ platform design. AGuIX@Tb-P1 was characterised for its photo-physical and physico-chemical properties. The effect of the nanoparticles was studied using human glioblastoma U-251 MG cells and was compared to treatment with AGuIX@ nanoparticles doped with Gadolinium (Gd) and P1 (AGuIX@Gd-P1). We demonstrated that the AGuIX@Tb-P1 design was consistent with X-ray photon energy transfer from Terbium to P1. Both nanoparticles had similar dark cytotoxicity and they were absorbed in a similar rate within the cells. Pre-treated cells exposure to X-rays was related to reactive species production. Using clonogenic assays, establishment of survival curves allowed discrimination of the impact of radiation treatment from X-ray-induced photodynamic effect. We showed that cell growth arrest was increased (35%-increase) when cells were treated with AGuIX@Tb-P1 compared to the nanoparticle doped with Gd.

TNFα secreted by glioma associated macrophages promotes endothelial activation and resistance against anti-angiogenic therapy

One of the most prominent features of glioblastoma (GBM) is hyper-vascularization. Bone marrow-derived macrophages are actively recruited to the tumor and referred to as glioma-associated macrophages (GAMs) which are thought to provide a critical role in tumor neo-vascularization. However, the mechanisms by which GAMs regulate endothelial cells (ECs) in the process of tumor vascularization and response to anti-angiogenic therapy (AATx) is not well-understood. Here we show that GBM cells secrete IL-8 and CCL2 which stimulate GAMs to produce TNFα. Subsequently, TNFα induces a distinct gene expression signature of activated ECs including VCAM-1, ICAM-1, CXCL5, and CXCL10. Inhibition of TNFα blocks GAM-induced EC activation both in vitro and in vivo and improve survival in mouse glioma models. Importantly we show that high TNFα expression predicts worse response to Bevacizumab in GBM patients. We further demonstrated in mouse model that treatment with B20.4.1.1, the mouse analog of Bevacizumab, increased macrophage recruitment to the tumor area and correlated with upregulated TNFα expression in GAMs and increased EC activation, which may be responsible for the failure of AATx in GBMs. These results suggest TNFα is a novel therapeutic that may reverse resistance to AATx. Future clinical studies should be aimed at inhibiting TNFα as a concurrent therapy in GBMs.

Towards an Image-Informed Mathematical Model of In Vivo Response to Fractionated Radiation Therapy

Simple Summary

Using medical imaging data and computational models, we develop a modeling framework to provide personalized treatment response forecasts to fractionated radiation therapy for individual tumors. We evaluate this approach in an animal model of brain cancer and forecast changes in tumor cellularity and vasculature.

Abstract

Fractionated radiation therapy is central to the treatment of numerous malignancies, including high-grade gliomas where complete surgical resection is often impractical due to its highly invasive nature. Development of approaches to forecast response to fractionated radiation therapy may provide the ability to optimize or adapt treatment plans for radiotherapy. Towards this end, we have developed a family of 18 biologically-based mathematical models describing the response of both tumor and vasculature to fractionated radiation therapy. Importantly, these models can be personalized for individual tumors via quantitative imaging measurements. To evaluate this family of models, rats (n = 7) with U-87 glioblastomas were imaged with magnetic resonance imaging (MRI) before, during, and after treatment with fractionated radiotherapy (with doses of either 2 Gy/day or 4 Gy/day for up to 10 days). Estimates of tumor and blood volume fractions, provided by diffusion-weighted MRI and dynamic contrast-enhanced MRI, respectively, were used to calibrate tumor-specific model parameters. The Akaike Information Criterion was employed to select the most parsimonious model and determine an ensemble averaged model, and the resulting forecasts were evaluated at the global and local level. At the global level, the selected model’s forecast resulted in less than 16.2% error in tumor volume estimates. At the local (voxel) level, the median Pearson correlation coefficient across all prediction time points ranged from 0.57 to 0.87 for all animals. While the ensemble average forecast resulted in increased error (ranging from 4.0% to 1063%) in tumor volume predictions over the selected model, it increased the voxel wise correlation (by greater than 12.3%) for three of the animals. This study demonstrates the feasibility of calibrating a model of response by serial quantitative MRI data collected during fractionated radiotherapy to predict response at the conclusion of treatment.

Preclinical Safety Evaluation of Intranasally Delivered Human Mesenchymal Stem Cells in Juvenile Mice

Simple Summary

The concept of utilizing mesenchymal stem cells for the treatment of central nervous system disorders has progressed from preclinical studies to clinical trials. While promising, the effectiveness of cell therapy is hampered by the route used to deliver cells into the brain. In this context, intranasal cell administration has boomed over the past few years as an effective cell delivery method. However, comprehensive safety studies are required before translation to the clinic. Our study shed light on how intranasally administrated mesenchymal stem cells may be used to safely treat neurological disorders.

Abstract

Mesenchymal stem cell (MSC)-based therapy is a promising therapeutic approach in the management of several pathologies, including central nervous system diseases. Previously, we demonstrated the therapeutic potential of human adipose-derived MSCs for neurological sequelae of oncological radiotherapy using the intranasal route as a non-invasive delivery method. However, a comprehensive investigation of the safety of intranasal MSC treatment should be performed before clinical applications. Here, we cultured human MSCs in compliance with quality control standards and administrated repeated doses of cells into the nostrils of juvenile immunodeficient mice, mimicking the design of a subsequent clinical trial. Short- and long-term effects of cell administration were evaluated by in vivo and ex vivo studies. No serious adverse events were reported on mouse welfare, behavioral performances, and blood plasma analysis. Magnetic resonance study and histological analysis did not reveal tumor formation or other abnormalities in the examined organs of mice receiving MSCs. Biodistribution study reveals a progressive disappearance of transplanted cells that was further supported by an absent expression of human GAPDH gene in the major organs of transplanted mice. Our data indicate that the intranasal application of MSCs is a safe, simple and non-invasive strategy and encourage its use in future clinical trials.

Development of a Prodrug of Camptothecin for Enhanced Treatment of Glioblastoma Multiforme

A novel therapeutic approach for glioblastoma multiforme (GBM) therapy has been carried out through in vitro and in vivo testing by using the prodrug camptothecin-20-O-(5-aminolevulinate) (CPT-ALA). The incorporation of ALA to CPT may promote uptake of the cytotoxic molecule by glioblastoma cells where the heme synthesis pathway is active, improving the therapeutic action and reducing the side effects over healthy tissue. The antitumor properties of CPT-ALA have been tested on different GBM cell lines (U87, U251, and C6) as well as in an orthotopic GBM model in rat, where potential toxicity in central nervous system cells was analyzed. In vitro results indicated no significant differences in the cytotoxic effect over the different GBM cell lines for CPT and CPT-ALA, albeit cell mortality induced by CPT over normal cell lines was significantly higher than CPT-ALA. Moreover, intracranial GBM in rat was significantly reduced (30% volume) with 2 weeks of CPT-ALA treatment with no significant side effects or alterations to the well-being of the animals tested. 5-ALA moiety enhances CPT diffusion into tumors due to solubility improvement and its metabolic-based targeting, increasing the CPT cytotoxic effect on malignant cells while reducing CPT diffusion to other proliferative healthy tissue. We demonstrate that CPT-ALA blocks proliferation of GBM cells, reducing the infiltrative capacity of GBM and promoting the success of surgical removal, which improves life expectancy by reducing tumor recurrence.

Targeting VPAC1 Receptors for Imaging Glioblastoma

PURPOSE

Scintigraphic imaging of malignant glioblastoma (MG) continues to be challenging. We hypothesized that VPAC1 cell surface receptors can be targeted for positron emission tomography (PET) imaging of orthotopically implanted MG in a mouse model, using a VPAC1-specific peptide [⁶⁴Cu]TP3805.

PROCEDURES

The expression of VPAC1 in mouse GL261 and human U87 glioma cell lines was determined by western blot. The ability of [⁶⁴Cu]TP3805 to bind to GL261 and U87 cells was studied by cell-binding. Receptor-blocking studies were performed to validate receptor specificity. GL261 tumors were implanted orthotopically in syngeneic T-bet knockout C57BL/6 mouse brain (N = 15) and allowed to grow for 2-3 weeks. Mice were injected i.v., first with ~ 150 μCi of 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) then 24 h later with ~ 200 μCi of [⁶⁴Cu]TP3805. In another set of tumor-bearing mice, (N = 5), ionic [⁶⁴Cu]Cl₂ was injected as a control. Mice were imaged at a 2-h post-injection using an Inveon micro-PET/CT, sacrificed and % ID/g of [⁶⁴Cu]TP3805 and [⁶⁴Cu]Cl₂ were calculated in a tumor, normal brain, and other tissues. For histologic tissue examination, 3-μm thick sections of the tumors and normal brain were prepared, digital autoradiography (DAR) was performed, and then the sections were H&E stained for histologic examination.

RESULTS

Western blots showed a strong signal for VPAC1 on both cell lines. [⁶⁴Cu]TP3805 cell-binding was 87 ± 1.5 %. Receptor-blocking reduced cell-binding to 24.3 ± 1.5 % (P < 0.01). PET imaging revealed remarkable accumulation of [⁶⁴Cu]TP3805 in GL261 MG with a negligible background in the normal brain, as compared to [¹⁸F]FDG. Micro-PET/CT image analyses and tissue distribution showed that the brain tumor uptake for [⁶⁴Cu]TP3805 was 8.2 ± 1.7 % ID/g and for [⁶⁴Cu]Cl₂ 2.1 ± 0.5 % ID/g as compared to 1.0 ± 0.3 % ID/g and 1.4 ± 0.3 % ID/g for normal mouse brains, respectively. The high tumor/normal brain ratio for [⁶⁴Cu]TP3805 (8.1 ± 1.1) allowed tumors to be visualized unequivocally. Histology and [⁶⁴Cu]TP3805 DAR differentiated malignant tumors from healthy brain and confirmed PET findings.

CONCLUSION

Targeting VPAC1 receptors using [⁶⁴Cu]TP3805 for PET imaging of MG is a promising novel approach and calls for further investigation.

AS602801 sensitizes glioma cells to temozolomide and vincristine by blocking gap junction communication between glioma cells and astrocytes

Previous studies showed that the chemotherapeutic effect of temozolomide (TMZ) and vincristine (VCR) against glioma might be blunted by the co‐culture with astrocytes, and connexin‐43 (CX43) was thought to play a vital role in the communication between glioma cells and astrocytes. In this study, we aimed to investigate the combined chemotherapeutic effect of AS602801 and TMZ/ VCR in glioma cells both. Dye transfer assay was used to evaluate the gap junction activity between U251 cells and astrocytes. Western blot and immunohistochemistry were carried out to analyse the expression of p‐JNK, CX43 and CASP‐3 proteins treated under different conditions. AS602801 significantly suppressed the gap junction activity between U251 cells and astrocytes. The expression of p‐JNK and CX43 was remarkably inhibited by AS602801. TMZ/VCR‐induced apoptosis of glioma cells was effectively enhanced by AS602801 treatment. Accordingly, the inhibitory role of TMZ/VCR in the expression of p‐JNK, CX43 and CASP‐3 in glioma cells was notably restored by AS602801. Furthermore, in a glioma cell xenograft, AS602801 showed an apparent capability to enhance TMZ/VCR‐induced tumour cell apoptosis through altering the expression of p‐JNK, CX43 and CASP‐3. The findings of this study demonstrated that the co‐culture of glioma cells with astrocytes blunted the tumour killing effect of TMZ and VCR. AS602801 down‐regulated CX43 expression by inhibiting JNK. And AS602801 also sensitized glioma cells to TMZ/VCR by blocking the gap junction communication between glioma cells and astrocytes via down‐regulating CX43, indicating its potential role as a novel adjuvant chemotherapeutic agent in the treatment of glioma.

Tumor Penetrating Peptide-Functionalized Tenascin-C Antibody for Glioblastoma Targeting

BACKGROUND

Conjugation to clinical-grade tumor penetrating iRGD peptide is a widely used strategy to improve tumor homing, extravasation, and penetration of cancer drugs and tumor imaging agents. The C domain of the extracellular matrix molecule Tenascin-C (TNC-C) is upregulated in solid tumors and represents an attractive target for clinical-grade single-chain antibody- based vehicles for tumor delivery drugs and imaging agents.

OBJECTIVE

To study the effect of C-terminal genetic fusion of the iRGD peptide to recombinant anti- TNC-C single-chain antibody clone G11 on systemic tumor homing and extravasation.

METHODS

Enzyme-linked immunosorbent assay was used to study the interaction of parental and iRGD-fused anti-TNC-C single-chain antibodies with C domain of tenascin-C and αVβ3 integrins. For systemic homing studies, fluorescein-labeled ScFV G11-iRGD and ScFV G11 antibodies were administered in U87-MG glioblastoma xenograft mice, and their biodistribution was studied by confocal imaging of tissue sections stained with markers of blood vessels and Tenascin C immunoreactivity.

RESULTS

In a cell-free system, iRGD fusion to ScFV G11 conferred the antibody has a robust ability to bind αVβ3 integrins. The fluorescein labeling of ScFV G11-iRGD did not affect its target binding activity. In U87-MG mice, iRGD fusion to ScFV G11 antibodies improved their homing to tumor blood vessels, extravasation, and penetration of tumor parenchyma.

CONCLUSION

The genetic fusion of iRGD tumor penetrating peptide to non-internalizing affinity targeting ligands may improve their tumor tropism and parenchymal penetration for more efficient delivery of imaging and therapeutic agents into solid tumor lesions.

Focused Ultrasound-Mediated Blood-Brain Barrier Opening Increases Delivery and Efficacy of Etoposide for Glioblastoma Treatment

PURPOSE

Glioblastoma (GBM) is a devastating disease. With the current treatment of surgery followed by chemoradiation, outcomes remain poor, with median survival of only 15 months and a 5-year survival rate of 6.8%. A challenge in treating GBM is the heterogeneous integrity of the blood-brain barrier (BBB), which limits the bioavailability of systemic therapies to the brain. There is a growing interest in enhancing drug delivery by opening the BBB with the use of focused ultrasound (FUS). We hypothesize that an FUS-mediated BBB opening can enhance the delivery of etoposide for a therapeutic benefit in GBM.

METHODS AND MATERIALS

A murine glioma cell line (Pdgf⁺, Pten^-/-, P53^-/-) was orthotopically injected into B6(Cg)-Tyrc-2J/J mice to establish the syngeneic GBM model for this study. Animals were treated with FUS and microbubbles to open the BBB to enhance the delivery of systemic etoposide. Magnetic resonance (MR) imaging was used to evaluate the BBB opening and tumor progression. Liquid chromatography tandem mass spectrometry was used to measure etoposide concentrations in the intracranial tumors.

RESULTS

The murine glioma cell line is sensitive to etoposide in vitro. MR imaging and passive cavitation detection demonstrate the safe and successful BBB opening with FUS. The combined treatment of an FUS-mediated BBB opening and etoposide decreased tumor growth by 45% and prolonged median overall survival by 6 days: an approximately 30% increase. The FUS-mediated BBB opening increased the brain tumor-to-serum ratio of etoposide by 3.5-fold and increased the etoposide concentration in brain tumor tissue by 8-fold compared with treatment without ultrasound.

CONCLUSIONS

The current study demonstrates that BBB opening with FUS increases intratumoral delivery of etoposide in the brain, resulting in local control and overall survival benefits.

Supramolecularly enabled pH- triggered drug action at tumor microenvironment potentiates nanomedicine efficacy against glioblastoma

The crucial balance of stability in blood-circulation and tumor-specific delivery has been suggested as one of the challenges for effective bench-to-bedside translation of nanomedicines (NMs). Herein, we developed a supramolecularly enabled tumor-extracellular (T^ex) pH-triggered NM that can maintain the micellar structure with the entrapped-drug during systemic circulation and progressively release drug in the tumor by rightly sensing heterogeneous tumor-pH. Desacetylvinblastine hydrazide (DAVBNH), a derivative of potent anticancer drug vinblastine, was conjugated to an aliphatic ketone-functionalized poly(ethylene glycol)-b-poly(amino acid) copolymer and the hydrolytic stability of the derived hydrazone bond was efficiently tailored by exploiting the compartmentalized structure of polymer micelle. We confirmed an effective and safe therapeutic application of T^ex pH-sensitive DAVBNH-loaded micelle (T^ex-micelle) in orthotopic glioblastoma (GBM) models, extending median survival to 1.4 times in GBM xenograft and 2.6 times in GBM syngeneic model, compared to that of the free DAVBNH. The work presented here offers novel chemical insights into the molecular design of smart NMs correctly sensing T^ex-pH via programmed functionalities. The practical engineering strategy based on a clinically relevant NM platform, and the encouraging therapeutic application of T^ex-micelle in GBM, one of the most lethal human cancers, thus suggests the potential clinical translation of this system against other types of common cancers, including GBM.

Glioma Cells With Genetically Engineered IGF-I Receptor Downregulation Can Persist in the Brain in a Dormant State

Glioblastoma multiforme is an aggressive malignancy, resistant to standard treatment modalities and associated with poor prognosis. We analyzed the role of the IGF system in intracerebral glioma growth using human and rat glioma cells. The glioma cells C6 and U87MG were transduced with a genetically engineered retrovirus expressing type 1 insulin-like growth factor (IGF-IR) antisense RNA, either before or after intra-cerebral implantation of the cells into Sprague Dawley rats or nude mice, respectively and tumor growth and animal survival were monitored. Rat glioma cells transduced prior to orthotopic, intra-cerebral implantation had a significantly increased apoptotic rate in vivo and a significantly reduced tumor volume as seen 24 days post implantation (p < 0.0015). This resulted in increased survival, as greater than 70% of the rats were still alive 182 days after tumor implantation (p < 0.01), as compared to 80% mortality by day 24 in the control group. Histomorphology and histochemical studies performed on brain tissue that was obtained from rats that survived for 182 days revealed numerous single cells that were widely disseminated throughout the brain. These cells expressed the β-galactosidase marker protein, but were Ki67negative, suggesting that they acquired a dormant phenotype. Direct targeting of the C6 cells with retroviral particles in vivo was effective and reduced tumor volumes by 22% relative to controls. A significant effect on tumor growth was also seen with human glioma U87MG cells that were virally transduced and implanted intra-cerebrally in nude mice. We observed in these mice a significant reduction in tumor volumes and 70% of the animals were still alive 6 months after tumor implantation, as compared to 100% mortality in the control group by day 63. Our results show that IGF-IR targeting can inhibit the intracerebral growth of glioma cells. They also suggest that IGF-IR expression levels may determine a delicate balance between glioma cell growth, death and the acquisition of a dormant state in the brain.

A practical method for multimodal registration and assessment of whole-brain disease burden using PET, MRI, and optical imaging

Many neurological diseases present with substantial genetic and phenotypic heterogeneity, making assessment of these diseases challenging. This has led to ineffective treatments, significant morbidity, and high mortality rates for patients with neurological diseases, including brain cancers and neurodegenerative disorders. Improved understanding of this heterogeneity is necessary if more effective treatments are to be developed. We describe a new method to measure phenotypic heterogeneity across the whole rodent brain at multiple spatial scales. The method involves co-registration and localized comparison of in vivo radiologic images (e.g. MRI, PET) with ex vivo optical reporter images (e.g. labeled cells, molecular targets, microvasculature) of optically cleared tissue slices. Ex vivo fluorescent images of optically cleared pathology slices are acquired with a preclinical in vivo optical imaging system across the entire rodent brain in under five minutes, making this methodology practical and feasible for most preclinical imaging labs. The methodology is applied in various examples demonstrating how it might be used to cross-validate and compare in vivo radiologic imaging with ex vivo optical imaging techniques for assessing hypoxia, microvasculature, and tumor growth.

Dehydrozingerone protects temozolomide-induced cognitive impairment in normal and C6 glioma rats besides enhancing its anticancer potential

Considering the cognitive impairment induced by temozolomide (TMZ) in glioblastoma survivors, the present study was aimed to evaluate the protective effect of dehydrozingerone (DHZ) against TMZ-induced cognitive impairment (chemobrain) and C6 cell line-induced glioma in male Wistar rats. In both chemobrain and glioma models, TMZ was administered at a dose of 18 mg/kg i.v every 5th day and DHZ at a dose of 100 mg/kg p.o. daily. Additionally, glioma was induced by intracerebral injection of 5 × 10⁴ C6 rat glioma cells in the cortex in the glioma model. Upon disease induction and treatment with TMZ + DHZ, spatial memory was assessed by the Morris water maze (MWM) test and episodic memory by the novel object recognition test (NORT). The induction of glioma was confirmed by histology of the cortex. Hippocampus and frontal cortex were subjected to antioxidant evaluation. Significant loss of spatial and episodic memory was observed with TMZ treatment which was significantly restored by DHZ. DHZ showed significant improvement in oxidative stress markers reversed the histopathological features in the cortex. TMZ-induced elevation of the glutathione level was also reversed by DHZ, indicating the role of DHZ in the reversal of TMZ resistance. In the glioma model, the improvement in cognition by DHZ correlated with the decrease in tumor volume. Altogether, the study results reveal the role of TMZ in worsening the memory and DHZ in reversing it, besides, improving its anticancer potential.

Feasibility of intratumoral 165Holmium siloxane delivery to induced U87 glioblastoma in a large animal model, the Yucatan minipig

Glioblastoma is the most aggressive primary brain tumor leading to death in most of patients. It comprises almost 50-55% of all gliomas with an incidence rate of 2-3 per 100,000. Despite its rarity, overall mortality of glioblastoma is comparable to the most frequent tumors. The current standard treatment combines surgical resection, radiotherapy and chemotherapy with temozolomide. In spite of this aggressive multimodality protocol, prognosis of glioblastoma is poor and the median survival remains about 12-14.5 months. In this regard, new therapeutic approaches should be developed to improve the life quality and survival time of the patient after the initial diagnosis. Before switching to clinical trials in humans, all innovative therapeutic methods must be studied first on a relevant animal model in preclinical settings. In this regard, we validated the feasibility of intratumoral delivery of a holmium (Ho) microparticle suspension to an induced U87 glioblastoma model. Among the different radioactive beta emitters, 166Ho emits high-energy β(-) radiation and low-energy γ radiation. β(-) radiation is an effective means for tumor destruction and γ rays are well suited for imaging (SPECT) and consequent dosimetry. In addition, the paramagnetic Ho nucleus is a good asset to perform MRI imaging. In this study, five minipigs, implanted with our glioblastoma model were used to test the injectability of 165Ho (stable) using a bespoke injector and needle. The suspension was produced in the form of Ho microparticles and injected inside the tumor by a technique known as microbrachytherapy using a stereotactic system. At the end of this trial, it was found that the 165Ho suspension can be injected successfully inside the tumor with absence or minimal traces of Ho reflux after the injections. This injection technique and the use of the 165Ho suspension needs to be further assessed with radioactive 166Ho in future studies.

Use of a Luciferase-Expressing Orthotopic Rat Brain Tumor Model to Optimize a Targeted Irradiation Strategy for Efficacy Testing with Temozolomide

Glioblastoma multiforme (GBM) is a common and aggressive malignant brain cancer with a mean survival time of approximately 15 months after initial diagnosis. Currently, the standard-of-care (SOC) treatment for this disease consists of radiotherapy (RT) with concomitant and adjuvant temozolomide (TMZ). We sought to develop an orthotopic preclinical model of GBM and to optimize a protocol for non-invasive monitoring of tumor growth, allowing for determination of the efficacy of SOC therapy using a targeted RT strategy combined with TMZ. A strong correlation (r = 0.80) was observed between contrast-enhanced (CE)-CT-based volume quantification and bioluminescent (BLI)-integrated image intensity when monitoring tumor growth, allowing for BLI imaging as a substitute for CE-CT. An optimized parallel-opposed single-angle RT beam plan delivered on average 96% of the expected RT dose (20, 30 or 60 Gy) to the tumor. Normal tissue on the ipsilateral and contralateral sides of the brain were spared 84% and 99% of the expected dose, respectively. An increase in median survival time was demonstrated for all SOC regimens compared to untreated controls (average 5.2 days, p < 0.05), but treatment was not curative, suggesting the need for novel treatment options to increase therapeutic efficacy.