Dynamic magnetic resonance imaging assessment of vascular targeting agent effects in rat intracerebral tumor models

IONPs-Based Medical Imaging in Cancer Care: Moving Beyond Traditional Diagnosis and Therapeutic Assessment

Cancer-related burden of morbidity and mortality is rapidly rising worldwide. Medical imaging plays an important role in every phase of cancer management, including diagnosis, staging, treatment planning and evaluation. Iron oxide nanoparticles (IONPs) could serve as contrast agents or labeling agents to enhance the identification and visualization of pathological tissues as well as target cells. Multimodal or multifunctional imaging can be easily acquired by modifying IONPs with other imaging agents or functional groups, allowing the accessibility of combined imaging techniques and providing more comprehensive information for cancer care. To date, IONPs-enhanced medical imaging has gained intensive application in early diagnosis, monitoring treatment as well as guiding radio-frequency ablation, sentinel lymph node dissection, radiotherapy and hyperthermia therapy. Besides, IONPs mediated imaging is also capable of promoting the development of anti-cancer nanomedicines through identifying patients potentially sensitive to nanotherapeutics. Based on versatile imaging modes and application fields, this review highlights and summarizes recent research advances of IONPs-based medical imaging in cancer management. Besides, currently existing challenges are also discussed to provide perspectives and advices for the future development of IONPs-based imaging in cancer management.

A randomized, double-blind, single-dose, parallel phase I clinical trial to compare the bioequivalence, immunogenicity and safety of bevacizumab biosimilar and bevacizumab in healthy Chinese subjects

BACKGROUND

Bevacizumab, a humanized monoclonal antibody against VEGF, can be used as a target therapy for colorectal cancer. A phase I clinical trial was conducted to compare the bioequivalence, immunogenicity and safety of bevacizumab biosimilar (Chia Tai Tianqing Pharmaceutical Group Co., Ltd.) and Bevacizumab (Roche Diagnostics GmbH) in healthy Chinese males.

RESEARCH DESIGN & METHOD

Healthy Chinese subjects (N = 98) were randomly divided into two groups. A single-dose bevacizumab biosimilar or Bevacizumab was given for per cycle. Plasma drug concentrations were detected by liquid chromatography-tandem mass spectrometry (LC-MC/MS) assay. We detected the levels of anti-drug antibody (ADA) to evaluate drug immunogenicity and the safety of drugs throughout the study.

RESULTS

The geometric mean ratios (GMRs) of AUC_0-t, C_max and AUC_0-∞ for bevacizumab biosimilar and Bevacizumab were 96.27%, 93.69% and 97.01%, respectively. The 90% CIs were all within 80%-125%, meeting the bioequivalence standards. The levels of ADA were similar. In addition, the two drugs both demonstrated excellent safety in the trial.

CONCLUSION

This study showed that bevacizumab biosimilar and Bevacizumab had similar pharmacokinetics (PK) parameters and safety in healthy Chinese subjects.

CLINICAL TRIAL REGISTRATION INFORMATION

This trial was registered in ClinicalTrials.gov (Number: NCT05476341, date registered: 25, Jul 2022) and Drug Clinical Trial Registration and Information Disclosure Platform (Number: CTR20171308, date registered: 16, Nov 2017).

Efficacy of surface-functionalized Mg1-x Co x Fe2O4 (0 ≤ x ≤ 1; Δx = 0.1) for hyperthermia and in vivo MR imaging as a contrast agent

Surface-functionalized Mg1-x Co x Fe2O4 (0 ≤ x ≤ 1; Δx = 0.1) can be an exciting candidate as an MRI contrast agent and for thermotherapeutic applications. The figure-of-merit, T 2, relaxivity, r 2, of MRI and specific loss power, SLP, of hyperthermia depend on the structural and magnetic properties of the nanoparticles. We synthesized cobalt-substituted magnesium ferrite Mg1-x Co x Fe2O4 (0 ≤ x ≤ 1 with Δx = 0.1) nanoparticles using a chemical co-precipitation method. The lattice parameter and average crystallite size increase with the increase in cobalt content. The force-constant of FTIR of the tetrahedral sites increases, and that of the octahedral sites decreases with an increase in cobalt content. The room temperature Mössbauer spectra of Mg1-x Co x Fe2O4 show that the Mössbauer absorption area of the A site decreases, and the Mössbauer absorption area of the B site increases with x. The Mössbauer spectra and M-H hysteresis loops at room temperature confirmed that a transition from fast relaxation (superparamagnetic) to mixed slow/fast (superparamagnetic/ferrimagnetic) relaxation occurs with changing cobalt content. The cobalt ion tends to occupy the octahedral B site, which makes the A-B interaction stronger; therefore, we see the above transition. Cytotoxicity experiments on HeLa cells revealed that both chitosan and chitosan-coated magnesium cobalt ferrite nanoparticles are biocompatible. In the Mg1-x Co x Fe2O4 series, both r 2 and SLP increase with x because of the increase in magnetization and anisotropy.

Perfusion parameters derived from MRI for preoperative prediction of IDH mutation and MGMT promoter methylation status in glioblastomas

PURPOSE

To investigate the feasibility for preoperative prediction of IDH mutation and MGMT promoter methylation status in glioblastomas(GBMs) by intravoxel incoherent motion(IVIM) and dynamic susceptibility contrast(DSC).

METHODS

Preoperative IVIM and DSC images of 71 patients(IDH mutation:45, IDH wildtype: 26; MGMT methylation: 31, MGMT unmethylation:40) with glioblastomas were analyzed retrospectively. Perfusion parameters including microcirculation perfusion coefficient(D*), perfusion fraction(f), cerebral blood volume(CBV) and cerebral blood flow(CBF) were measured. Corrected perfusion parameters containing corrected perfusion coefficient(ADC_perf) and simplified perfusion fraction(SPF) were from the simplified IVIM with 3 b values. Correlations among parameters were analyzed by Spearman correlation. All parameters were compared with Mann-Whitney U test. Univariate and multivariate logistic regression models were constructed. The receiver operating characteristic(ROC) curve was analyzed.

RESULTS

The IVIM parameters showed merely moderate correlations with CBV and showed no correlation with CBF. IDH mutation GBMs showed lower D*, ADC_perf, SPF, CBV and higher f than IDH wildtype GBMs(all p < 0.05). D* was the independent predictor for IDH mutation with the highest AUC of 0.912(95%CI: 0.821-0.966). The D*, ADC_perf, SPF and CBV of MGMT promoter methylation GBMs were lower than unmethylation GBMs while f was higher(all p < 0.05). Multivariate model showed the highest prediction efficacy for MGMT promoter methylation with an AUC of 0.915(95%CI: 0.824-0.968). The CBF was not useful in distinguishing IDH mutation and MGMT promoter methylation status(p = 0.055, 0.215).

CONCLUSION

IDH mutation and MGMT promoter methylation status in GBMs can be assessed effectively by IVIM and DSC. Besides, D* was the independent predictor of IDH mutation status.

The potential for remodelling the tumour vasculature in glioblastoma

Despite significant improvements in the clinical management of glioblastoma, poor delivery of systemic therapies to the entire population of tumour cells remains one of the biggest challenges in the achievement of more effective treatments. On the one hand, the abnormal and dysfunctional tumour vascular network largely limits blood perfusion, resulting in an inhomogeneous delivery of drugs to the tumour. On the other hand, the presence of an intact blood-brain barrier (BBB) in certain regions of the tumour prevents chemotherapeutic drugs from permeating through the tumour vessels and reaching the diseased cells. In this review we analyse in detail the implications of the presence of a dysfunctional vascular network and the impenetrable BBB on drug transport. We discuss advantages and limitations of the currently available strategies for remodelling the tumour vasculature aiming to ameliorate the above mentioned limitations. Finally we review research methods for visualising vascular dysfunction and highlight the power of DCE- and DSC-MRI imaging to assess changes in blood perfusion and BBB permeability.

Assessment of bevacizumab resistance increased by expression of BCAT1 in IDH1 wild-type glioblastoma: application of DSC perfusion MR imaging

BCAT1 (branched-chain amino acid trasaminase1) expression is necessary for the progression of IDH1 wild-type (WT) glioblastoma multiforme (GBM), which is known to be associated with aggressive tumors. The purpose of our study is to investigate the bevacizumab resistance increased by the expression of BCAT1 in IDH1 WT GBM in a rat model, which was evaluated using DSC perfusion MRI. BCAT1 sh#1 inhibits cell proliferation and limits cell migration potential in vitro. In vivo MRI showed that the increase in both tumor volume and nCBV after bevacizumab treatment in IDH1 WT tumors was significantly higher compared with BCAT1 sh#1tumors. In a histological analysis, more micro-vessel reformation by bevacizumab resistance was observed in IDH1 WT tumors than BCAT1 sh#1 tumors. These findings indicate that BCAT1 expression in IDH1 WT GBM increases resistance to bevacizumab treatment, which could be assessed by DSC perfusion MRI, and that nCBV can be a surrogate imaging biomarker for the prediction of antiangiogenic treatment in GBM.

Discriminating MGMT promoter methylation status in patients with glioblastoma employing amide proton transfer-weighted MRI metrics

OBJECTIVES

To explore the feasibility of using amide proton transfer-weighted (APTw) MRI metrics as surrogate biomarkers to identify the O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation status in glioblastoma (GBM).

METHODS

Eighteen newly diagnosed GBM patients, who were previously scanned at 3T and had a confirmed MGMT methylation status, were retrospectively analysed. For each case, a histogram analysis in the tumour mass was performed to evaluate several quantitative APTw MRI metrics. The Mann-Whitney test was used to evaluate the difference in APTw parameters between MGMT methylated and unmethylated GBMs, and the receiver-operator-characteristic analysis was further used to assess diagnostic performance.

RESULTS

Ten GBMs were found to harbour a methylated MGMT promoter, and eight GBMs were unmethylated. The mean, variance, 50th percentile, 90th percentile and Width_10-90 APTw values were significantly higher in the MGMT unmethylated GBMs than in the MGMT methylated GBMs, with areas under the receiver-operator-characteristic curves of 0.825, 0.837, 0.850, 0856 and 0.763, respectively, for the discrimination of MGMT promoter methylation status.

CONCLUSIONS

APTw signal metrics have the potential to serve as valuable imaging biomarkers for identifying MGMT methylation status in the GBM population.

KEY POINTS

• APTw-MRI is applied to predict MGMT promoter methylation status in GBMs. • GBMs with unmethylated MGMT promoter present higher APTw-MRI than methylated GBMs. • Multiple APTw histogram metrics can identify MGMT methylation status. • Mean APTw values showed the highest diagnostic accuracy (AUC = 0.825).

High αv Integrin Level of Cancer Cells Is Associated with Development of Brain Metastasis in Athymic Rats

BACKGROUND/AIM

Brain metastases commonly occur in patients with malignant skin, lung and breast cancers resulting in high morbidity and poor prognosis. Integrins containing an αv subunit are cell adhesion proteins that contribute to cancer cell migration and cancer progression. We hypothesized that high expression of αv integrin cell adhesion protein promoted metastatic phenotypes in cancer cells.

MATERIALS AND METHODS

Cancer cells from different origins were used and studied regarding their metastatic ability and intetumumab, anti-αv integrin mAb, sensitivity using in vitro cell migration assay and in vivo brain metastases animal models.

RESULTS

The number of brain metastases and the rate of occurrence were positively correlated with cancer cell αv integrin levels. High αv integrin-expressing cancer cells showed significantly faster cell migration rate in vitro than low αv integrin-expressing cells. Intetumumab significantly inhibited cancer cell migration in vitro regardless of αv integrin expression level. Overexpression of αv integrin in cancer cells with low αv integrin level accelerated cell migration in vitro and increased the occurrence of brain metastases in vivo.

CONCLUSION

αv integrin promotes brain metastases in cancer cells and may mediate early steps in the metastatic cascade, such as adhesion to brain vasculature. Targeting αv integrin with intetumumab could provide clinical benefit in treating cancer patients who develop metastases.

Prediction of Anti-cancer Nanotherapy Efficacy by Imaging

Anticancer nanotherapeutics have shown mixed results in clinical trials, raising the questions of whether imaging should be used to i) identify patients with a higher likelihood of nanoparticle accumulation, ii) assess nanotherapeutic efficacy before traditional measures show response, and iii) guide adjuvant treatments to enhance therapeutic nanoparticle (TNP) delivery. Here we review the use of a clinically approved MRI nanoparticle (ferumoxytol, FMX) to predict TNP delivery and efficacy. It is becoming increasingly apparent that nanoparticles used for imaging, despite clearly distinct physicochemical properties, often co-localize with TNP in tumors. This evidence offers the possibility of using FMX as a generic “companion diagnostic” nanoparticle for multiple TNP formulations, thus potentially allowing many of the complex regulatory and cost challenges of other approaches to be avoided.

A continuous-infusion dynamic MRI model at 3.0 Tesla for the serial quantitative evaluation of microvascular proliferation in an animal model of glioblastoma multiforme

PURPOSE

To develop a continuous-infusion dynamic MRI technique to characterize tumor-associated microvascular proliferation (MVP) in a rat brain model of glioblastoma multiforme.

METHODS

The proposed model assumes effects due to tumor-associated MVP (eg, vascular permeability, K^trans ; intravascular plasma fraction, v_p ) cannot be individually separated and solves for a single parameter (k^vasc ) that quantifies the T₁ -weighted contrast enhancement from dynamic images acquired during continuous contrast agent (CA) infusion. Untreated C6 tumor-bearing animals (N = 6) were serially imaged on postoperative days (PODs) 14 and 18 with a 3 Tesla clinical scanner utilizing a dynamic spatial and temporal resolution of 0.38 × 0.38 × 1.5 mm³ and 3.47 s, respectively.

RESULTS

An association was present between PODs 14 and 18 for median tumor k^vasc (Pearson's r = 0.94, P = 0.0052) and CA concentration ([CA], derived from pre- and postcontrast R₁ maps; r = 0.94, P = 0.0054). On POD 18, there was a voxel-based association between k^vasc and [CA] within each tumor (0.45 < r < 0.82, P < 0.001). However, voxel-based subregions demonstrated a reduced association between k^vasc and [CA] (N = 5; -0.08 < r < 0.22, P > 0.05) or an inverse association (N = 1; r = -0.28, P = 0.001), indicating differences between locations of vascular permeability and subsequent CA pooling in tumors.

CONCLUSION

The continuous-infusion method may provide a quantitative measure for characterizing and monitoring tumor-associated MVP. Magn Reson Med 78:1824-1838, 2017. © 2017 International Society for Magnetic Resonance in Medicine.

Alk5 inhibition increases delivery of macromolecular and protein-bound contrast agents to tumors

Limited transendothelial permeability across tumor microvessels represents a significant bottleneck in the development of tumor-specific diagnostic agents and theranostic drugs. Here, we show an approach to increase transendothelial permeability of macromolecular and nanoparticle-based contrast agents via inhibition of the type I TGF-β receptor, activin-like kinase 5 (Alk5), in tumors. Alk5 inhibition significantly increased tumor contrast agent delivery and enhancement on imaging studies, while healthy organs remained relatively unaffected. Imaging data correlated with significantly decreased tumor interstitial fluid pressure, while tumor vascular density remained unchanged. This immediately clinically translatable concept involving Alk5 inhibitor pretreatment prior to an imaging study could be leveraged for improved tumor delivery of macromolecular and nanoparticle-based imaging probes and, thereby, facilitate development of more sensitive imaging tests for cancer diagnosis, enhanced tumor characterization, and personalized, image-guided therapies.

Improved Treatment Efficacy of Antiangiogenic Therapy when Combined with Picornavirus Vaccination in the GL261 Glioma Model

The addition of antiangiogenic therapy to the standard-of-care treatment regimen for recurring glioblastoma has provided some clinical benefits while also delineating numerous caveats, prompting evaluation of the elicited alterations to the tumor microenvironment. Of critical importance, given the steadily increasing incorporation of immunotherapeutic approaches clinically, is an enhanced understanding of the interplay between angiogenic and immune response pathways within tumors. In the present study, the GL261 glioma mouse model was used to determine the effects of antiangiogenic treatment in an immune-competent host. Following weekly systemic administration of aflibercept, an inhibitor of vascular endothelial growth factor, tumor volume was assessed by magnetic resonance imaging and changes to the tumor microenvironment were determined. Treatment with aflibercept resulted in reduced tumor burden and increased survival compared with controls. Additionally, decreased vascular permeability and preservation of the integrity of tight junction proteins were observed. Treated tumors also displayed hallmarks of anti-angiogenic evasion, including marked upregulation of vascular endothelial growth factor expression and increased tumor invasiveness. Aflibercept was then administered in combination with a picornavirus-based antitumor vaccine and tumor progression was evaluated. This combination therapy significantly delayed tumor progression and extended survival beyond that observed for either therapy alone. As such, this work demonstrates the efficacy of combined antiangiogenic and immunotherapy approaches for treating established gliomas and provides a foundation for further evaluation of the effects of antiangiogenic therapy in the context of endogenous or vaccine-induced inflammatory responses.

VB-111: a novel anti-vascular therapeutic for glioblastoma multiforme

Glioblastoma multiforme (GBM) is among the most highly vascularized of solid tumors, contributing to the infiltrative nature of the disease, and conferring poor outcome. Due to the critical dependency of GBM on growth of new endothelial vasculature, we evaluated the preclinical activity of a novel adenoviral gene therapy that targets the endothelium within newly formed blood vessels for apoptosis. VB-111, currently in phase II clinical trials, consists of a non-replicating Adenovirus 5 (El deleted) carrying a proapoptotic human Fas-chimera (transgene) under the control of a modified murine promoter (PPE-1-3×) which specifically targets endothelial cells within the tumor vasculature. Here we report that a single intravenous dose of 2.5 × 10(11) or 1 × 10(11) VPs was sufficient to extend survival in nude rats bearing U87MG-luc2 or nude mice bearing U251-luc, respectively. Bioluminescence imaging of nude rats showed that VB-111 effectively inhibited tumor growth within four weeks of treatment. This was confirmed in a select group of animals by MRI. In our mouse model we observed that 3 of 10 nude mice treated with VB-111 completely lost U251 luciferase signal and were considered long term survivors. To assess the antiangiogenic effects of VB-111, we evaluated the tumor-associated microvaculature by CD31, a common marker of neovascularization, and found a significant decrease in the microvessel density by IHC. We further assessed the neovasculature by confocal microscopy and found that VB-111 inhibits vascular density in two separate mouse models bearing U251-RFP xenografts. Collectively, this study supports the clinical development of VB-111 as a treatment for GBM.

Unsanctifying the sanctuary: challenges and opportunities with brain metastases

While the use of targeted therapies, particularly radiosurgery, has broadened therapeutic options for CNS metastases, patients respond minimally and prognosis remains poor. The inability of many systemic chemotherapeutic agents to penetrate the blood-brain barrier (BBB) has limited their use and allowed brain metastases to become a burgeoning clinical challenge. Adequate preclinical models that appropriately mimic the metastatic process, the BBB, and blood-tumor barriers (BTB) are needed to better evaluate therapies that have the ability to enhance delivery through or penetrate into these barriers and to understand the mechanisms of resistance to therapy. The heterogeneity among and within different solid tumors and subtypes of solid tumors further adds to the difficulties in determining the most appropriate treatment approaches and methods of laboratory and clinical studies. This review article discusses therapies focused on prevention and treatment of CNS metastases, particularly regarding the BBB, and the challenges and opportunities these therapies present.

Chemotherapy in glioma

The treatment of glial brain tumors begins with surgery, and standard adjuvant treatment at the end of the past millennium for high-grade glioma and high-risk low-grade glioma was radiotherapy and chemotherapy was given at recurrence. However, over the past 10 years much has changed regarding the role of chemotherapy in gliomas and it is now clear that chemotherapy has a role in the treatment of almost all newly diagnosed diffuse gliomas (WHO grade II-IV). This is the result of several prospective studies that showed survival benefit after combined chemoradiotherapy with temozolomide in glioblastoma (WHO grade IV) or after procarbazine, CCNU (lomustine) and vincristine chemotherapy in diffuse low-grade (WHO grade II) and anaplastic (WHO grade III) glioma. The current standard of treatment for diffuse gliomas is described in this overview and in addition some attention is given to targeted therapies.

Vascular endothelial growth factor blockade alters magnetic resonance imaging biomarkers of vascular function and decreases barrier permeability in a rat model of lung cancer brain metastasis

Background

Blockade of vascular endothelial growth factor (VEGF) to promote vascular normalization and inhibit angiogenesis has been proposed for the treatment of brain metastases; however, vascular normalization has not been well-characterized in this disease. We investigated the effect of treatment with bevacizumab anti-VEGF antibody on magnetic resonance imaging (MRI) biomarkers of brain tumor vascular characteristics in comparison to small molecule delivery in a rat model of human lung cancer brain metastasis.

Methods

Athymic rats with A549 human lung adenocarcinoma intracerebral xenografts underwent MRI at 11.75 T before and one day after treatment with bevacizumab (n = 8) or saline control (n = 8) to evaluate tumor volume, free water content (edema), blood volume and vascular permeability (K^trans). One day later, permeability to ¹⁴C-aminoisobutyric acid (AIB) was measured in tumor and brain to assess the penetration of a small drug-like molecule.

Results

In saline control animals, tumor volume, edema and permeability increased over the two day assessment period. Compared to controls, bevacizumab treatment slowed the rate of tumor growth (P = 0.003) and blocked the increase in edema (P = 0.033), but did not alter tumor blood volume. Bevacizumab also significantly reduced K^trans (P = 0.033) and AIB passive permeability in tumor (P = 0.04), but not to peritumoral tissue or normal brain. Post-treatment K^trans correlated with AIB levels in the bevacizumab-treated rats but not in the saline controls.

Conclusions

The correlation of an MRI biomarker for decreased vascular permeability with decreased AIB concentration in tumor after antiangiogenic treatment suggests that bevacizumab partially restored the normal low permeability characteristics of the blood–brain barrier in a model of human lung cancer brain metastasis.

Development and validation of an open source quantification tool for DSC-MRI studies

MOTIVATION

This work presents the development of an open source tool for the quantification of dynamic susceptibility-weighted contrast-enhanced (DSC) perfusion studies. The development of this tool is motivated by the lack of open source tools implemented on open platforms to allow external developers to implement their own quantification methods easily and without the need of paying for a development license.

MATERIALS AND METHODS

This quantification tool was developed as a plugin for the ImageJ image analysis platform using the Java programming language. A modular approach was used in the implementation of the components, in such a way that the addition of new methods can be done without breaking any of the existing functionalities. For the validation process, images from seven patients with brain tumors were acquired and quantified with the presented tool and with a widely used clinical software package. The resulting perfusion parameters were then compared.

RESULTS

Perfusion parameters and the corresponding parametric images were obtained. When no gamma-fitting is used, an excellent agreement with the tool used as a gold-standard was obtained (R(2)>0.8 and values are within 95% CI limits in Bland-Altman plots).

CONCLUSION

An open source tool that performs quantification of perfusion studies using magnetic resonance imaging has been developed and validated using a clinical software package. It works as an ImageJ plugin and the source code has been published with an open source license.

Functional dynamic contrast-enhanced magnetic resonance imaging in an animal model of brain metastases: a pilot study

Background

Brain metastasis is a common disease with a poor prognosis. The purpose of this study is to test feasibility and safety of the animal models for brain metastases and to use dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to enhance detection of brain metastases.

Methods

With approval from the institutional animal ethics committee, 18 New Zealand rabbits were randomly divided into three groups: Group A received an intra-carotid infusion (ICI) of mannitol followed by VX2 cells; group B received successive ICI of mannitol and heparin followed by VX2 cells; and group C received an ICI of normal saline. The survival rate and clinical symptoms were recorded after inoculation. After two weeks, conventional MRI and DCE-MRI were performed using 3.0 Tesla scanner. The number of tumors and detection rate were analyzed. After MRI measurements, the tumors were stained with hematoxylin-eosin.

Results

No rabbits died during the procedure. The rabbits had common symptoms, including loss of appetite, lassitude and lethargy, etc. at 10.8±1.8 days and 8.4±1.5 days post-inoculation in group A and B, respectively. Each animal in groups A and B re-gained the lost weight within 14 days. Brain metastases could be detected by MRI at 14 days post-inoculation in both groups A and B, with metastases manifesting as nodules in the brain parenchyma and thickening in the meninges. DCE-MRI increased the total detection of tumors compared to non-contrast MRI (P<0.05). The detection rates of T1-weighted image, T2-weighted image and DCE-MRI were 12%, 32% and 100%, respectively (P<0.05). Necropsy revealed nodules or thickening meninges in the gross samples and VX2 tumor cytomorphologic features in the slides, which were consistent with the MRI results.

Conclusions

The VX2 rabbit model of brain metastases is feasible, as verified by MRI and pathologic findings, and may be a suitable platform for future studies of brain metastases. Functional DCE-MRI can be used to evaluate brain metastases in a rabbit model.

Cerebral blood volume estimation by ferumoxytol-enhanced steady-state MRI at 9.4 T reveals microvascular impact of α1 -adrenergic receptor antibodies

Cerebrovascular abnormality is frequently accompanied by cognitive dysfunctions, such as dementia. Antibodies against the α1 -adrenoceptor (α1 -AR) can be found in patients with Alzheimer's disease with cerebrovascular disease, and have been shown to affect the larger vessels of the brain in rodents. However, the impact of α1 -AR antibodies on the cerebral vasculature remains unclear. In the present study, we established a neuroimaging method to measure the relative cerebral blood volume (rCBV) in small rodents with the ultimate goal to detect changes in blood vessel density and/or vessel size induced by α1 -AR antibodies. For this purpose, mapping of R2 * and R2 was performed using MRI at 9.4 T, before and after the injection of intravascular iron oxide particles (ferumoxytol). The change in the transverse relaxation rates (ΔR2 *, ΔR2 ) showed a significant rCBV decrease in the cerebrum, cortex and hippocampus of rats (except hippocampal ΔR2 ), which was more pronounced for ΔR2 * than for ΔR2 . Immunohistological analyses confirmed that the α1 -AR antibody induced blood vessel deficiencies. Our findings support the hypothesis that α1 -AR antibodies lead to cerebral vessel damage throughout the brain, which can be monitored by MRI-derived rCBV, a non-invasive neuroimaging method. This demonstrates the value of rCBV estimation by ferumoxytol-enhanced MRI at 9.4 T, and further underlines the significance of this antibody in brain diseases involving vasculature impairments, such as dementia.

Delivery of chemotherapeutics across the blood-brain barrier: challenges and advances

The blood-brain barrier (BBB) limits drug delivery to brain tumors. We utilize intraarterial infusion of hyperosmotic mannitol to reversibly open the BBB by shrinking endothelial cells and opening tight junctions between the cells. This approach transiently increases the delivery of chemotherapy, antibodies, and nanoparticles to brain. Our preclinical studies have optimized the BBB disruption (BBBD) technique and clinical studies have shown its safety and efficacy. The delivery of methotrexate-based chemotherapy in conjunction with BBBD provides excellent outcomes in primary central nervous system lymphoma (PCNSL) including stable or improved cognitive function in survivors a median of 12 years (range 2-26 years) after diagnosis. The addition of rituximab to chemotherapy with BBBD for PCNSL can be safely accomplished with excellent overall survival. Our translational studies of thiol agents to protect against platinum-induced toxicities led to the development of a two-compartment model in brain tumor patients. We showed that delayed high-dose sodium thiosulfate protects against carboplatin-induced hearing loss, providing the framework for large cooperative group trials of hearing chemoprotection. Neuroimaging studies have identified that ferumoxytol, an iron oxide nanoparticle blood pool agent, appears to be a superior contrast agent to accurately assess therapy-induced changes in brain tumor vasculature, in brain tumor response to therapy, and in differentiating central nervous system lesions with inflammatory components. This chapter reviews the breakthroughs, challenges, and future directions for BBBD.

[Personalized neurooncology]

The treatment of patients with intrinsic brain tumors is radically changing. This change is currently not (yet) signified by the use of targeted therapy in clinical practice but more by the definition of molecular markers as predictors for response to therapy which have been used for a long time. While in the past the choice of treatment has been based solely on the tumor entity and its degree of malignancy derived from histological analyses, large randomized trials have now provided a solid basis for personalized molecular-guided treatment decisions. For instance, in the German NOA-08 trial a benefit of chemotherapy with temozolomide alone was only demonstrated in a subgroup of elderly patients with malignant gliomas displaying promoter hypermethylation of the DNA repair enzyme MGMT. This is only one of several examples where molecular analysis of tumor tissue becomes clinically relevant as these analyses can and should be taken into account for treatment decisions and not, as previously, just as an additional parameter for estimating prognosis. This article illustrates the current developments in the area of personalized neurooncology and critically reviews the impact on clinical decision-making in daily practice.

Malignant astrocytoma in elderly patients: where do we stand?

PURPOSE OF REVIEW

Age is inversely correlated with clinical outcome and a strong prognostic factor for the course of most primary brain tumors including malignant astrocytoma, i.e. anaplastic astrocytoma and glioblastoma. We here review available clinical outcome data and discuss future directions of clinical research.

RECENT FINDINGS

The standard of care in patients with malignant astrocytoma above the range of 65-70 years was considered radiotherapy, preferentially using a hypofractionated regimen (15 × 2.66 Gy). Two phase III clinical trials, the NOA-08 and Nordic trials, demonstrated that temozolomide (TMZ) therapy alone was not inferior to radiotherapy alone, and methylation of the O-methylguanine-DNA-methyltransferase (MGMT) gene promoter was predictive with a methylated MGMT promoter indicating a benefit from TMZ chemotherapy. Ongoing clinical trials in this patient population include the National Cancer Institute of Canada/European Organisation for Research and Treatment of Cancer intergroup trial, investigating the combination of hypofractionated radiotherapy and TMZ chemotherapy, and the Swiss ARTE trial, investigating the combination of bevacizumab and hypofractionated radiotherapy. Recent translational studies indicate that prognostically favorable factors in malignant astrocytoma from younger patients are virtually absent in the elderly.

SUMMARY

Current standard of care for elderly patients with malignant astrocytoma involves a treatment strategy based on the MGMT gene promoter methylation status. The role of combined radiotherapy and TMZ chemotherapy and a potential role for the addition of anti-VEGF therapy to radiotherapy are currently addressed in ongoing trials. The lack of favorable prognostic factors in tumor tissue might in part explain the poorer clinical outcome of elderly patients.

Focused ultrasound simultaneous irradiation/MRI imaging, and two-stage general kinetic model

Many studies have investigated how to use focused ultrasound (FUS) to temporarily disrupt the blood-brain barrier (BBB) in order to facilitate the delivery of medication into lesion sites in the brain. In this study, through the setup of a real-time system, FUS irradiation and injections of ultrasound contrast agent (UCA) and Gadodiamide (Gd, an MRI contrast agent) can be conducted simultaneously during MRI scanning. By using this real-time system, we were able to investigate in detail how the general kinetic model (GKM) is used to estimate Gd penetration in the FUS irradiated area in a rat's brain resulting from UCA concentration changes after single FUS irradiation. Two-stage GKM was proposed to estimate the Gd penetration in the FUS irradiated area in a rat's brain under experimental conditions with repeated FUS irradiation combined with different UCA concentrations. The results showed that the focal increase in the transfer rate constant of K_trans caused by BBB disruption was dependent on the doses of UCA. Moreover, the amount of in vivo penetration of Evans blue in the FUS irradiated area in a rat's brain under various FUS irradiation experimental conditions was assessed to show the positive correlation with the transfer rate constants. Compared to the GKM method, the Two-stage GKM is more suitable for estimating the transfer rate constants of the brain treated with repeated FUS irradiations. This study demonstrated that the entire process of BBB disrupted by FUS could be quantitatively monitored by real-time dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

Enhanced primary tumor delineation in pancreatic adenocarcinoma using ultrasmall super paramagnetic iron oxide nanoparticle-ferumoxytol: an initial experience with histopathologic correlation

Purpose

To evaluate the role of ferumoxytol-enhanced magnetic resonance imaging (MRI) in delineating primary pancreatic tumors in patients undergoing preoperative neoadjuvant therapy.

Materials and methods

Eight patients with pancreatic adenocarcinoma were enrolled in this study, and underwent MRI scans at baseline, immediate post, and at the 48 hour time point after ferumoxytol injection with quantitative T2* sequences. The patients were categorized into two groups; group A received preoperative neoadjuvant therapy and group B did not. The T2* of the primary pancreatic tumor and adjacent parenchyma was recorded at baseline and the 48 hour time point. After surgery, the primary tumors were assessed histopathologically for fibrosis and inflammation.

Results

The mean T2* of the primary tumor and adjacent parenchyma at 48 hours in group A were 22.11 ms and 16.34 ms, respectively; in group B, these values were 23.96 ms and 23.26 ms, respectively. The T2* difference between the tumor and adjacent parenchyma in group A was more pronounced compared to in group B. The tumor margins were subjectively more distinct in group A compared to group B. Histopathologic evaluation showed a rim of dense fibrosis with atrophic acini at the periphery of the lesion in group A. Conversely, intact tumor cells/glands were present at the periphery of the tumor in group B.

Conclusion

Ferumoxytol-enhanced MRI scans in patients receiving preoperative neoadjuvant therapy may offer enhanced primary tumor delineation, contributing towards achieving disease-free margin at the time of surgery, and thus improving the prognosis of pancreatic carcinomas.

Inhibition of SUR1 decreases the vascular permeability of cerebral metastases

Inhibition of sulfonylurea receptor 1 (SUR1) by glyburide has been shown to decrease edema after subarachnoid hemorrhage. We investigated if inhibiting SUR1 reduces cerebral edema due to metastases, the most common brain tumor, and explored the putative association of SUR1 and the endothelial tight junction protein, zona occludens-1 (ZO-1). Nude rats were intracerebrally implanted with small cell lung carcinoma (SCLC) LX1 or A2058 melanoma cells (n = 36). Rats were administered vehicle, glyburide (4.8 µg twice, orally), or dexamethasone (0.35 mg, intravenous). Blood-tumor barrier (BTB) permeability (K (trans)) was evaluated before and after treatment using dynamic contrast-enhanced magnetic resonance imaging. SUR1 and ZO-1 expression was evaluated using immunofluorescence and Western blots. In both models, SUR1 expression was significantly increased (P < .05) in tumors. In animals with SCLC, control mean K (trans) (percent change ± standard error) was 101.8 ± 36.6%, and both glyburide (-21.4 ± 14.2%, P < .01) and dexamethasone (-14.2 ± 13.1%, P < .01) decreased BTB permeability. In animals with melanoma, compared to controls (117.1 ± 43.4%), glyburide lowered BTB permeability increase (3.2 ± 15.4%, P < .05), while dexamethasone modestly lowered BTB permeability increase (63.1 ± 22.1%, P > .05). Both glyburide (P < .001) and dexamethasone (P < .01) decreased ZO-1 gap formation. By decreasing ZO-1 gaps, glyburide was at least as effective as dexamethasone at halting increased BTB permeability caused by SCLC and melanoma. Glyburide is a safe, inexpensive, and efficacious alternative to dexamethasone for the treatment of cerebral metastasis-related vasogenic edema.

MRI assessment of experimental gliomas using 17.6 T

INTRODUCTION

Using ultra-high-field contrast-enhanced magnetic resonance imaging (MRI), an increase of field strength is associated with a decrease of T 1 relaxivity. Yet, the impact of this effect on signal characteristics and contrast-enhanced pathology remains unclear. Hence, we evaluated the potential of a 17.6-T MRI to assess contrast-enhancing parts of experimentally induced rat gliomas compared to 3 T.

METHODS

A total of eight tumor-bearing rats were used for MRI assessments either at 17.6 T (four rats) or at 3 T (four rats) at 11 days after stereotactic implantation of F98 glioma cells into the right frontal lobe. T 1-weighted sequences were used to investigate signal-to-noise-ratios, contrast-to-noise-ratios, and relative contrast enhancement up to 16 min after double-dose contrast application. In addition, tumor volumes were calculated and compared to histology.

RESULTS

The 17.6-T-derived contrast-enhancing volumes were 31.5 ± 15.4 mm(3) at 4 min, 38.8 ± 12.7 mm(3) at 8 min, 51.1 ± 12.6 mm(3) at 12 min, and 61.5 ± 10.8 mm(3) at 16 min after gadobutrol injection. Corresponding histology-derived volumes were clearly higher (138.8 ± 8.4 mm(3); P < 0.01). At 3 T, contrast-enhancing volumes were 85.2 ± 11.7 mm(3) at 4 min, 107.3 ± 11.0 mm(3) at 8 min, 117.0 ± 10.5 mm(3) at 12 min, and 129.1 ± 10.0 mm(3) at 16 min after contrast agent application. Averaged histology-derived volumes (139.1 ± 13.4 mm(3)) in this group were comparable to the 16-min volume (P ↔16 min = 0.38). Compared to ultra-high-field MRI, all 3-T-derived volumes were significantly higher (P < 0.02).

CONCLUSION

Compared to 3-T-derived images and histology, tumor volumes were underestimated by approximately 50 % at 17.6 T. Hence, contrast-enhanced 17.6-T MRI provided no further benefits in tumor measurement compared to 3 T.

Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) in Preclinical Studies of Antivascular Treatments

Antivascular treatments can either be antiangiogenic or targeting established tumour vasculature. These treatments affect the tumour microvasculature and microenvironment but may not change clinical measures like tumour volume and growth. In research on antivascular treatments, information on the tumour vasculature is therefore essential. Preclinical research is often used for optimization of antivascular drugs alone or in combined treatments. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is an in vivo imaging method providing vascular information, which has become an important tool in both preclinical and clinical research. This review discusses common DCE-MRI imaging protocols and analysis methods and provides an overview of preclinical research on antivascular treatments utilizing DCE-MRI.

Targeting αV-integrins decreased metastasis and increased survival in a nude rat breast cancer brain metastasis model

Brain metastases commonly occur in patients with breast, lung and melanoma systemic cancers. The anti-α(V) integrin monoclonal antibody intetumumab binds cell surface proteins important for adhesion, invasion and angiogenesis in the metastatic cascade. The objective of this study was to investigate the anti-metastatic effect of intetumumab in a hematogenous breast cancer brain metastasis model. Female nude rats received intra-carotid infusion of human brain-seeking metastatic breast cancer cells (231BR-HER2) and were randomly assigned into four groups: (1) control; (2) intetumumab mixed with cells in vitro 5 min before infusion without further treatment; (3) intetumumab intravenously 4 h before and weekly after cell infusion; (4) intetumumab intravenously weekly starting 7 days after cell infusion. Brain metastases were detected by magnetic resonance imaging (MRI) and immunohistochemistry. Comparisons were made using the Kruskal-Wallis test and Dunnett's test. Survival times were estimated using Kaplan-Meier analysis. All control rats with brain tissue available for histology (9 of 11 rats) developed multiple brain metastases (median = 14). Intetumumab treatment either in vitro prior to cell infusion or intravenous before or after cell infusion prevented metastasis formation on MRI and decreased the number of metastases on histology (median = 2, p = 0.0055), including 30 % of animals without detectable tumors at the end of the study. The overall survival was improved by intetumumab compared to controls (median 77+ vs. 52 days, p = 0.0277). Our results suggest that breast cancer patients at risk of metastases might benefit from early intetumumab treatment.

The impact of bevacizumab on temozolomide concentrations in intracranial U87 gliomas

PURPOSE

An important question in the sequencing of anti-cancer therapies in patients with glioblastoma (GBM) is whether concurrent anti-angiogenesis therapies improve or impair brain concentrations of concomitantly administered cytotoxic therapies. The purpose of this study is to assess the intratumoral disposition of temozolomide (TMZ) via microdialysis before and after bevacizumab in an intracranial GBM xenograft model.

METHODS

Microdialysis probes were placed within tumor and contralateral brain in athymic rats bearing U87 intracerebral gliomas. TMZ (50 mg/kg oral) was administered 10 days thereafter. Extracellular fluid (ECF) was collected for 6 h. BEV was administered (10 mg/kg IV), and TMZ was re-dosed (50 mg/kg oral) 36 h thereafter with additional ECF collection. All ECF samples were assessed for TMZ concentration with liquid chromatography-tandem mass spectrometry.

RESULTS

Tumor TMZ mean area under the concentration-time curve (AUC(0-∞)) was 3.35 μg h/mL pre-BEV. Post-BEV, tumor mean TMZ AUC(0-∞) was 3.98 μg h/mL. In non-tumor brain, mean TMZ AUC(0-∞) pre-BEV was 3.22 μg h/mL and post-BEV was 3.34 μg h/mL.

CONCLUSIONS

There were no statistically significant changes in TMZ pharmacokinetics before or after BEV in the athymic rat U87 intracranial glioma model. BEV and TMZ are being investigated as a combination therapy in several ongoing studies for patients with glioma. These data reassuringly suggest that BEV does not significantly change the ECF tumor concentrations of TMZ in either tumor-bearing or normal brain when dosed 36 h prior to TMZ.

Dose dense 1 week on/1 week off temozolomide in recurrent glioma: a retrospective study

Alternative temozolomide regimens have been proposed to overcome O(6)-methylguanine-DNA methyltransferase mediated resistance. We investigated the efficacy and tolerability of 1 week on/1 week off temozolomide (ddTMZ) regimen in a cohort of patients treated with ddTMZ between 2005 and 2011 for the progression of a glioblastoma during or after chemo-radiation with temozolomide or a recurrence of another type of glioma after radiotherapy and at least one line of chemotherapy. Patients received ddTMZ at 100-150 mg/m(2)/d (days 1-7 and 15-21 in cycles of 28-days). All patients had a contrast enhancing lesion on MRI and the response was assessed by MRI using the RANO criteria; complete and partial responses were considered objective responses. Fifty-three patients were included. The median number of cycles of ddTMZ was 4 (range 1-12). Eight patients discontinued chemotherapy because of toxicity. Two of 24 patients with a progressive glioblastoma had an objective response; progression free survival at 6 months (PFS-6) in glioblastoma was 29%. Three of the 16 patients with a recurrent WHO grade 2 or 3 astrocytoma or oligodendroglioma or oligo-astrocytoma without combined 1p and 19q loss had an objective response and PFS-6 in these patients was 38%. Four out of the 12 evaluable patients with a recurrent WHO grade 2 or 3 oligodendroglioma or oligo-astrocytoma with combined 1p and 19q loss had an objective response; PFS-6 in these patients was 62%. This study indicates that ddTMZ is safe and effective in recurrent glioma, despite previous temozolomide and/or nitrosourea chemotherapy. Our data do not suggest superior efficacy of this schedule as compared to the standard day 1-5 every 4 weeks schedule.

MRI of metastasis-permissive microenvironments

One of the earliest documented observations of the importance of the microenvironment in metastasis was made by Stephen Paget in 1889. More than a century later, the metastatic cascade remains a major cause of mortality from cancer. Cancer meets the criterion of a successful organization that is able to survive by adapting to changing environments. In fact, the tumor microenvironment and stroma are co-opted and shaped by cancer cells to derive a survival advantage. Cohesive strategies integrating advances in molecular biology and chemistry, with noninvasive multimodality imaging, provide new insights into the role of the tumor microenvironment in promoting metastasis from primary tumors as well as insights into environments that attract and permit cancer cells to establish colonies in distant organs. This article provides an overview of molecular and functional imaging characterization of microenvironments that can promote or permit cancer cells to metastasize and the microenvironmental characteristics of distant metastases.

Improved perfusion MR imaging assessment of intracerebral tumor blood volume and antiangiogenic therapy efficacy in a rat model with ferumoxytol

PURPOSE

To evaluate the consistency of tumor blood volume measurements and antiangiogenic therapy efficacy assessments with a low-molecular-weight gadolinium-based contrast agent (GBCA, gadodiamide) versus an iron oxide nanoparticle (ferumoxytol) in the presence or absence of a loading dose of contrast agent before perfusion magnetic resonance (MR) imaging (preload method).

MATERIALS AND METHODS

The protocol was approved by the institutional animal care and use committee. U87MG tumor cells were implanted intracerebrally in 13 rats. All 13 rats underwent 11.75-T MR imaging with gadodiamide (60 μL) 13 days after tumor implantation. The next day, nine rats underwent MR imaging with ferumoxytol (60 μL). Immediately after ferumoxytol imaging, six rats received bevacizumab (45 mg/kg). MR imaging was repeated 48 hours after bevacizumab treatment with gadodiamide and 72 hours after treatment with ferumoxytol. Each study included three consecutive dynamic susceptibility-weighted contrast material-enhanced (DSC) MR acquisitions, which were performed without preload, with single-dose preload, and with double-dose preload. Tumor relative cerebral blood volume (rCBV) was estimated from each DSC MR acquisition. Two-way repeated measures analysis of variance was performed to test for differences between groups with both contrast agents.

RESULTS

DSC MR imaging with gadodiamide and without preload showed low rCBV (≤ 1.75) in nine of the 13 tumors; estimated rCBV increased progressively with both single- and double-dose preloads (P < .001). Conversely, rCBVs obtained with ferumoxytol were high (>1.75) and remained constant with all three acquisitions. The magnitude of rCBV decrease after bevacizumab administration was dependent on the dose of gadodiamide preload, whereas the magnitude of rCBV decrease with ferumoxytol was constant regardless of whether contrast agent preload was used.

CONCLUSION

With GBCA, tumor rCBV can be underestimated without preload and becomes dose dependent with preload correction. Conversely, ferumoxytol provides consistent assessment of tumor rCBV and antiangiogenic therapy efficacy.