Surgical management of high-grade gliomas

Development of immunotherapy for high-grade gliomas: Overcoming the immunosuppressive tumor microenvironment

The preclinical and clinical development of novel immunotherapies for the treatment of central nervous system (CNS) tumors is advancing at a rapid pace. High-grade gliomas (HGG) are aggressive tumors with poor prognoses in both adult and pediatric patients, and innovative and effective therapies are greatly needed. The use of cytotoxic chemotherapies has marginally improved survival in some HGG patient populations. Although several challenges exist for the successful development of immunotherapies for CNS tumors, recent insights into the genetic alterations that define the pathogenesis of HGG and their direct effects on the tumor microenvironment (TME) may allow for a more refined and targeted therapeutic approach. This review will focus on the TME in HGG, the genetic drivers frequently found in these tumors and their effect on the TME, the development of immunotherapy for HGG, and the practical challenges in clinical trials employing immunotherapy for HGG. Herein, we will discuss broadly the TME and immunotherapy development in HGG, with a specific focus on glioblastoma multiforme (GBM) as well as additional discussion in the context of the pediatric HGG diagnoses of diffuse midline glioma (DMG) and diffuse hemispheric glioma (DHG).

Targeting Neuroinflammation in Brain Cancer: Uncovering Mechanisms, Pharmacological Targets, and Neuropharmaceutical Developments

Gliomas are one of the most lethal types of cancers accounting for ∼80% of all central nervous system (CNS) primary malignancies. Among gliomas, glioblastomas (GBM) are the most aggressive, characterized by a median patient survival of fewer than 15  months. Recent molecular characterization studies uncovered the genetic signatures and methylation status of gliomas and correlate these with clinical prognosis. The most relevant molecular characteristics for the new glioma classification are IDH mutation, chromosome 1p/19q deletion, histone mutations, and other genetic parameters such as ATRX loss, TP53, and TERT mutations, as well as DNA methylation levels. Similar to other solid tumors, glioma progression is impacted by the complex interactions between the tumor cells and immune cells within the tumor microenvironment. The immune system’s response to cancer can impact the glioma’s survival, proliferation, and invasiveness. Salient characteristics of gliomas include enhanced vascularization, stimulation of a hypoxic tumor microenvironment, increased oxidative stress, and an immune suppressive milieu. These processes promote the neuro-inflammatory tumor microenvironment which can lead to the loss of blood-brain barrier (BBB) integrity. The consequences of a compromised BBB are deleteriously exposing the brain to potentially harmful concentrations of substances from the peripheral circulation, adversely affecting neuronal signaling, and abnormal immune cell infiltration; all of which can lead to disruption of brain homeostasis. In this review, we first describe the unique features of inflammation in CNS tumors. We then discuss the mechanisms of tumor-initiating neuro-inflammatory microenvironment and its impact on tumor invasion and progression. Finally, we also discuss potential pharmacological interventions that can be used to target neuro-inflammation in gliomas.

Main genetic differences in high-grade gliomas may present different MR imaging and MR spectroscopy correlates

OBJECTIVE

To assess whether the main genetic differences observed in high-grade gliomas (HGG) will present different MR imaging and MR spectroscopy correlates that could be used to better characterize lesions in the clinical setting.

METHODS

Seventy-nine patients with histologically confirmed HGG were recruited. Immunohistochemistry analyses for isocitrate dehydrogenase gene 1 (IDH1), alpha thalassemia mental retardation X-linked gene (ATRX), Ki-67, and p53 protein expression were performed. Tumour radiological features were examined on MR images. Metabolic profile and infiltrative pattern were assessed with MR spectroscopy. MR features were analysed to identify imaging-molecular associations. The Kaplan-Meier method and the Cox regression model were used to identify survival prognostic factors.

RESULTS

In total, 17.7% of the lesions were IDH1-mutated, 8.9% presented ATRX-mutated, 70.9% presented p53 unexpressed, and 22.8% had Ki-67 > 5%. IDH1 wild-type tumours had higher levels of mobile lipids (p = 0.001). The tumour-infiltrative pattern was higher in HGG with unexpressed p53 (p = 0.009). Mutated ATRX tumours presented higher levels of glutamate and glutamine (Glx) (p = 0.001). An association was observed between Glx tumour levels (p = 0.038) and Ki-67 expression (p = 0.008) with the infiltrative pattern. Survival analyses identified IDH1 status, age, and tumour choline levels as independent predictors of prognostic significance.

CONCLUSIONS

Our results suggest that IDH1-wt tumours are more necrotic than IDH1-mut. And that the presence of an infiltrative pattern in HGG is associated with loss of p53 expression, Ki-67 index, and Glx levels. Finally, tumour choline levels could be used as a predictive factor in survival in addition to the IDH1 status to provide a more accurate prediction of survival in HGG patients.

KEY POINTS

• IDH1-wt tumours present higher levels of mobile lipids than IDH1-mut. • Mutated ATRX tumours exhibit higher levels of glutamate and glutamine. • Loss of p53 expression, Ki-67 expression, and glutamate and glutamine levels may contribute to the presence of an infiltrative pattern in HGG.

Principles of surgery for malignant astrocytomas

Malignant astrocytomas constitute the most aggressive and common primary tumors of the central nervous system. The standard treatment protocol for these tumors involves maximum safe surgical resection with adjuvant chemoradiotherapy. Despite numerous advances in surgical techniques and adjuncts, as well as the ongoing renaissance in the genetic and molecular characterization of these tumors, malignant astrocytomas continue to be associated with poor prognosis, with median overall survival averaging 15 months for grade IV astrocytomas after standard-of-care treatment. In this article, the goals, principles, techniques, prognostic factors, and modern outcomes of malignant astrocytoma surgery are reviewed. Particular attention is paid to contemporary methods of neuronavigation and functional mapping, the prognostic significance of the extent of resection, surgically delivered adjunctive therapies, and future avenues of research.

Present and potential future issues in glioblastoma treatment

The treatment of glioblastomas requires a multidisciplinary approach that takes the presently incurable nature of the disease into consideration. Treatments are multimodal and include surgery, radiotherapy and chemotherapy. Current recommendations are that patients with glioblastomas should undergo maximum surgical resection, followed by concurrent radiation and chemotherapy with the novel alkylating drug temozolomide. This is then to be followed by additional adjuvant temozolomide for a period of up to 6 months. Major advances in surgical and imaging technologies used to treat glioblastoma patients are described. These technologies include magnetic resonance imaging and metabolic data that are helpful in the diagnosis and guiding of surgical resection. However, glioblastomas almost invariably recur near their initial sites. Disease progression usually occurs within 6 months and leads rapidly to death. A number of signaling pathways can be activated constitutively in migrating glioma cells, thus rendering these cells resistant to proapoptotic insults, such as conventional chemotherapies. Therefore, the molecular and cellular therapies and local drug delivery that could be used to complement conventional treatments are described, and some of the currently ongoing clinical trials are reviewed, with respect to these new approaches.

Promoter hypermethylation and expression profile of MGMT and CDH1 genes in oral cavity cancer

BACKGROUND

Several genetic alterations have been reported to contribute to the development of oral squamous cell carcinoma (OSCC). Methylation of CpG-islands in cancer-related genes may serve as epigenetic biomarkers for oral cancer diagnosis and prognosis. The objective of this study was to analyze methylation profile of MGMT and CDH1 genes and their link with expression activity in patients with oral cavity cancer.

METHODS

Promoter hypermethylation status of MGMT and CDH1 genes were assayed by Methylation-specific PCR (MSP) in OSCC (n=76) tissues kept in paraffin and normal oral tissues (n=57) served as control. Also, we investigated MGMT and CDH1 mRNA levels by real-time quantities reverse transcripts PCR. Methylation and mRNA expression profiles of these genes and their association with clinical data were determined.

RESULTS

Aberrant promoter hypermethylation of CDH1 and MGMT genes were detected in 61.8% (47 of 76) and 73.7% (56 of 76) of the OSCC cases, respectively, with significant difference between cases and controls for MGMT (P=0.027). CDH1 promoter methylation in cases and healthy controls was not significant. The mRNA expression level results showed statistically significant (P=0.03) differences between cases and healty controls for the MGMT gene. However, the difference for the CDH1 gene was not significant.

CONCLUSION

Our findings, for the first time, in a South-Eastern Iranian population, indicate that the two genes are aberrantly methylated in OSCC, and that MGMT methylation may be considered as a potential molecular marker for the poor survival in advanced OSCC.

Molecular imaging of cancer: MR spectroscopy and beyond

Proton magnetic resonance spectroscopic imaging is a non-invasive diagnostic tool for the investigation of cancer metabolism. As an adjunct to morphologic and dynamic magnetic resonance imaging, it is routinely used for the staging, assessment of treatment response, and therapy monitoring in brain, breast, and prostate cancer. Recently, its application was extended to other cancerous diseases, such as malignant soft-tissue tumours, gastrointestinal and gynecological cancers, as well as nodal metastasis. In this review, we discuss the current and evolving clinical applications of proton magnetic resonance spectroscopic imaging. In addition, we will briefly discuss other evolving techniques, such as phosphorus magnetic resonance spectroscopic imaging, sodium imaging and diffusion-weighted imaging in cancer assessment.

Sterile alpha motif containing domain 9 is involved in death signaling of malignant glioma treated with inactivated Sendai virus particle (HVJ-E) or type I interferon

Malignant glioma is one of the most aggressive cancers. For the development of effective therapeutic strategies against such malignant diseases, elucidation of molecular targets is necessary. We found that inactivated Sendai virus particle (HVJ-E) induced extensive cell death in the human glioblastoma cell line U251MG. Intradermal U251MG tumors were more effectively suppressed by HVJ-E than interferon (IFN)-beta. From microarray analysis of gene expression in U251MG cells treated with HVJ-E, we focused on the up-regulation of sterile alpha motif containing domain 9 (SAMD9) gene. The expression of the SAMD9 gene was induced by administration of recombinant human IFN-alpha, -beta or -gamma. The up-regulation of the SAMD9 gene by HVJ-E treatment was abrogated by IFN receptor blocking antibody or JAK inhibitor treatment. When SAMD9 expression was knocked down by RNA interference, apoptotic cell death induced by HVJ-E was blocked in U251MG cells. Suppression of SAMD9 using SAMD9 siRNA also inhibited IFN-beta-induced death in U251MG cells with a small, but significant, difference to control groups. However, overexpression of the SAMD9 gene failed to induce significant cell death in U251MG cells. Thus, SAMD9 could be a key molecule to control cancer cell death by HVJ-E or IFN-beta treatment.

High incidence of MGMT and RARbeta promoter methylation in primary glioblastomas: association with histopathological characteristics, inflammatory mediators and clinical outcome

Glioblastomas, the most frequent primary brain tumors in adults, are characterized by a highly aggressive, inflammatory and angiogenic phenotype. Methylation of CpG islands in cancer-related genes may serve as an epigenetic biomarker for glioblastoma diagnosis and prognosis. The aim of this study was to analyze the methylation status of four critical tumor-associated genes (MGMT, RARbeta, RASSF1A, CDH13), and investigate possible links with inflammatory (interleukin [IL]-6, IL-8) and angiogenic mediators (vascular endothelial growth factor [VEGF], cyclooxygenase [COX]-2) and clinical outcome in 23 glioma samples (6 grade II astrocytomas, 17 grade IV glioblastomas). RARbeta and MGMT genes were more frequently methylated in 70.58% and 58.8% of glioblastomas, respectively. RASSF1A and CDH13 displayed a similar methylation frequency (23.52%) in glioblastomas. No gene methylation was observed in grade II astrocytomas. Tumor grade correlated positively with MGMT and RARbeta methylation (P = 0.005 and P = 0.019, respectively) and the extent of necrosis (P = 0.001 and P = 0.003). Interestingly, the marker of chronic inflammation, IL-6, was positively associated with methylation of MGMT (P = 0.004), RARbeta (P = 0.002), and RASSF1A (P = 0.0081) as well as the total number of methylated genes (P < 0.0001), indicating the important role of IL-6 in maintaining promoter methylation of these genes. VEGF expression correlated positively with MGMT and RARbeta methylation although these relationships were of marginal significance (P = 0.0679 and P = 0.0757). Kaplan-Meier univariate survival analysis indicated an unfavorable survival period in patients with MGMT methylation compared with those without methylation (P = 0.0474). Our study highlights the implication of MGMT and RARbeta methylation in the aggressive phenotype of primary glioblastomas. The association of MGMT methylation with clinical outcome indicates its potential prognostic value.

Analysis of interleukin (IL)-8 expression in human astrocytomas: associations with IL-6, cyclooxygenase-2, vascular endothelial growth factor, and microvessel morphometry

Malignant astrocytomas are highly vascular neoplasms with potent angiogenic activity. The present study aimed to investigate peripheral and local expression of interleukin (IL)-8 in astrocytomas with possible associations to IL-6, cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF) expression, and microvessel morphometry. IL-6- and IL-8-secreting peripheral blood monocytes (PBMCs) were evaluated in 17 glioblastoma (WHO grade IV), 5 anaplastic astrocytoma (WHO grade III), and 6 diffuse astrocytoma patients (WHO grade II), in parallel with 23 healthy controls using enzyme-linked immunosorbent spot (ELISPOT) assay. The IL-8 expression was assessed immunohistochemically in patients' tumor tissue sections and correlated with the expression of COX-2, VEGF, IL-6, and microvessel morphometry (assessed using CD34 antibody). Eighteen cases were also stained for CD31 and used as an additional vessel marker to validate our results regarding microvessel morphometry. IL-6 and IL-8 were highly secreted in the PBMCs of glioma patients compared with controls (p = 0.0001, p < 0.0001, respectively), with a positive correlation between IL-8 expression and secretion levels (p = 0.001). IL-8 immunoreactivity was detected in malignant cells or macrophages in perivascular areas and in pseudopalisading cells around necrosis and was positively correlated with histological grade (p = 0.0175) and tumor necrosis (p = 0.0793). IL-6 and IL-8 expression levels were positively correlated (p = 0.0036) and associated with COX-2 and VEGF expression (IL-6: p = 0.0133, p = 0.065; IL-8: p = 0.0139, p = 0.0101), but not with microvessel morphometry, by either CD31 or CD34. The coordinate expression and topographical relationship of IL-6, IL-8, COX-2, and VEGF in the same tumor areas (e.g., perinecrotic areas) attest to their intimate liaison in terms of cancer-induced angiogenesis, which is probably secondary to the induction of multiple interdependent molecular pathways. Moreover, our study seems to be the first attempt to link IL-8 expression by tumor cells with histological grade, implicating its potent role in gliomagenesis.

Present and potential future adjuvant issues in high-grade astrocytic glioma treatment

Despite major advances in the management of malignant gliomas of which glioblastomas represent the ultimate grade of malignancy, they remain characterized by dismal prognoses. Glioblastoma patients have a median survival expectancy of only 14 months on the current standard treatment of surgical resection to the extent feasible, followed by adjuvant radiotherapy plus temozolomide, given concomitantly with and after radiotherapy. Malignant gliomas are associated with such dismal prognoses because glioma cells can actively migrate through the narrow extra-cellular spaces in the brain, often travelling relatively long distances, making them elusive targets for effective surgical management. Clinical and experimental data have demonstrated that invasive malignant glioma cells show a decrease in their proliferation rates and a relative resistance to apoptosis (type I programmed cell death) as compared to the highly cellular centre of the tumor, and this may contribute to their resistance to conventional pro-apoptotic chemotherapy and radiotherapy. Resistance to apoptosis results from changes at the genomic, transcriptional and post-transcriptional level of proteins, protein kinases and their transcriptional factor effectors. The PTEN/ PI3K/Akt/mTOR/NF-kappaB and the Ras/Raf/MEK/ERK signaling cascades play critical roles in the regulation of gene expression and prevention of apoptosis. Components of these pathways are mutated or aberrantly expressed in human cancer, notably glioblastomas. Monoclonal antibodies and low molecular-weight kinase inhibitors of these pathways are the most common classes of agents in targeted cancer treatment. However, most clinical trials of these agents as monotherapies have failed to demonstrate survival benefit. Despite resistance to apoptosis being closely linked to tumorigenesis, tumor cells can still be induced to die by non-apoptotic mechanisms such as necrosis, senescence, autophagy (type II programmed cell death) and mitotic catastrophe. Temozolomide brings significant therapeutic benefits in glioblastoma treatment. Part of temozolomide cytotoxic activity is exerted through pro-autophagic processes and also through the induction of late apoptosis. Autophagy, type II programmed cell death, represents an alternative mechanism to overcome, at least partly, the dramatic resistance of many cancers to pro-apoptotic-related therapies. Another way to potentially overcome apoptosis resistance is to decrease the migration of malignant glioma cells in the brain, which then should restore a level of sensitivity to pro-apoptotic drugs. Recent series of studies have supported the concept that malignant gliomas might be seen as an orchestration of cross-talks between cancer cells, microenvironment, vasculature and cancer stem cells. The present chapter focuses on (i) the major signaling pathways making glioblastomas resistant to apoptosis, (ii) the signaling pathways distinctly activated by pro-autophagic drugs as compared to pro-apoptotic ones, (iii) autophagic cell death as an alternative to combat malignant gliomas, (iv) the major scientific data already obtained by researchers to prove that temozolomide is actually a pro-autophagic and pro-apoptotic drug, (v) the molecular and cellular therapies and local drug delivery which could be used to complement conventional treatments, and a review of some of the currently ongoing clinical trials, (vi) the fact that reducing the levels of malignant glioma cell motility can restore pro-apoptotic drug sensitivity, (vii) the observation that inhibiting the sodium pump activity reduces both glioma cell proliferation and migration, (viii) the brain tumor stem cells as a target to complement conventional treatment.

Survivin-driven and fiber-modified oncolytic adenovirus exhibits potent antitumor activity in established intracranial glioma

The poor prognosis of patients with malignant gliomas necessitates the development of novel therapies. Virotherapy, using genetically engineered adenovectors that selectively replicate in and kill neoplastic cells, represents one such strategy. In this study, we examined several oncolytic vectors with modified transcriptional and transductional control of viral replication. First, we incorporated the survivin promoter (S) to drive E1A gene expression. We then modified the adenovirus serotype 5 (Ad5) fiber protein via genetic knob switching or incorporation of peptide ligands to target the following glioma-associated receptors: the Ad3 attachment protein, or CD46, alpha(v) beta(3)/alpha(v)beta(5) integrins, or heparan sulfate proteoglycans. The three conditionally replicative adenoviruses, CRAd-S-5/3, CRAd-S-RGD, and CRAd-S-pk7, were then examined in vitro with respect to transduction efficiency and tissue specificity. The most promising virus was then tested in vivo for evidence of tumor growth inhibition. CRAd-S-pk7 provided the highest level of viral replication and tumor oncolysis in glioma cell lines. At the same time, we observed minimal viral replication and toxicity in normal human brain. Injection of CRAd-S-pk7 inhibited xenograft tumor growth by more than 300% (p < 0.001). Sixty-seven percent of treated mice with intracranial tumors were long-term survivors (>110 days; p < 0.005). Analysis of tumor tissue indicated increased adenoviral infectivity, decreased mitotic activity, and enhanced tumor apoptosis. These findings demonstrate the effectiveness of CRAd-S-pk7 and provide the rationale for further development of this novel oncolytic virus for glioma gene therapy.

Comparative analysis of peripheral and localised cytokine secretion in glioblastoma patients

BACKGROUND

Malignant gliomas are the most common primary brain tumours of both children and adults. The unique aspects of their biology and anatomic site render them refractory to conventional therapeutic strategies such as surgery and chemotherapy. Significant attention has been given, recently, to immunotherapy which, although promising in preclinical studies, has not yet enhanced the survival of patients with glioblastomas.

METHODS

To further understand the immunobiology of glioblastomas in clinical settings, we examined the secretion of four main cytokines in the peripheral blood and in primary cell cultures of 33 human glioblastoma patients. An ELISPOT methodology was used for the first time to examine Th1, and Th2 cytokine secretion from both peripheral lymphocytes and glioma tumour cells.

RESULTS

Th1 cytokines (tumour necrosis factor (TNF-alpha), interferon (IFN-gamma) were markedly reduced compared to control levels (P=0.01 and P<0.001, respectively), whereas in contrast, Th2 (interleukin (IL)-4 and IL-10) were strongly expressed in both peripheral lymphocytes and glioma cell cultures (P=0.05 and P<0.001, respectively).

CONCLUSION

This pattern indicates an 'immunosuppressive status' in glioblastomas which is related to their origination and the evasion of glioma cells from immune surveillance and could account for the failure of immunotherapy in such tumours. Furthermore, ELISPOT methodology can be used for monitoring of cytokine secretion from tumour cells, in addition to the well-established peripheral cytokine secretion.

Emerging Role of Combination of All-trans Retinoic Acid and Interferon-gamma as Chemoimmunotherapy in the Management of Human Glioblastoma

Glioblastoma is the most malignant and common type of brain tumor with devastating outcome. Because current treatment modalities are mostly ineffective in controlling and curing glioblastoma, new and innovative therapeutic strategies must be developed. This article describes recent advances in chemoimmunotherapy, which is combination of chemotherapy and immunotherapy, against glioblastoma. We provide an overview of available treatment options for glioblastomas, gaps in our knowledge of immune recognition of these malignant tumors, and chemotherapeutic and immunotherapeutic agents that need to be further explored for designing novel chemoimmunotherapeutic strategy for the management of human glioblastomas. Our recent study demonstrated that combination of the chemotherapeutic agent all-trans retinoic acid (ATRA) and the immunotherapeutic agent interferon-gamma (IFN-gamma) could concurrently induce differentiation, apoptotic death, and immune components in two different human glioblastoma cell lines. We propose that combination of ATRA and IFN-gamma can become an efficacious chemoimmunotherapy for the treatment of human glioblastoma.

High-resolution contrast-enhanced, susceptibility-weighted MR imaging at 3T in patients with brain tumors: correlation with positron-emission tomography and histopathologic findings

BACKGROUND AND PURPOSE

The purpose of this work was to demonstrate susceptibility effects (SusE) in various types of brain tumors with 3T high-resolution (HR)-contrast-enhanced (CE)-susceptibility-weighted (SW)-MR imaging and to correlate SusE with positron-emission tomography (PET) and histopathology.

MATERIALS AND METHODS

Eighteen patients with brain tumors, scheduled for biopsy or tumor extirpation, underwent high-field (3T) MR imaging. In all of the patients, an axial T1-spin-echo (SE) sequence and an HR-SW imaging sequence before and after IV application of a standard dose of contrast agent (MultiHance) was obtained. Seven patients preoperatively underwent PET. The frequency and formation of intralesional SusE in all of the images were evaluated and correlated with tumor grade as determined by PET and histopathology. Direct correlation of SusE and histopathologic specimens was performed in 6 patients. Contrast enhancement of the lesions was assessed in both sequences.

RESULTS

High-grade lesions demonstrated either high or medium frequency of SusE in 90% of the patients. Low-grade lesions demonstrated low frequency of SusE or no SusE. Correlation between intralesional frequency of SusE and histopathologic, as well as PET, tumor grading was statistically significant. Contrast enhancement was equally visible in both SW and SE sequences. Side-to-side comparison of tumor areas with high frequency of SusE and histopathology revealed that intralesional SusE reflected conglomerates of increased tumor microvascularity.

CONCLUSIONS

3T HR-CE-SW-MR imaging shows both intratumoral SusE not visible with standard MR imaging and contrast enhancement visible with standard MR imaging. Because frequency of intratumoral SusE correlates with tumor grade as determined by PET and histopathology, this novel technique is a promising tool for noninvasive differentiation of low-grade from high-grade brain tumors and for determination of an optimal area of biopsy for accurate tumor grading.