Genetic profiling of a distant second glioblastoma multiforme after radiotherapy: Recurrence or second primary tumor?

Recurrent Glioblastoma Treatment: State of the Art and Future Perspectives in the Precision Medicine Era

Current treatment guidelines for the management of recurrent glioblastoma (rGBM) are far from definitive, and the prognosis remains dismal. Despite recent advancements in the pharmacological and surgical fields, numerous doubts persist concerning the optimal strategy that clinicians should adopt for patients who fail the first lines of treatment and present signs of progressive disease. With most recurrences being located within the margins of the previously resected lesion, a comprehensive molecular and genetic profiling of rGBM revealed substantial differences compared with newly diagnosed disease. In the present comprehensive review, we sought to examine the current treatment guidelines and the new perspectives that polarize the field of neuro-oncology, strictly focusing on progressive disease. For this purpose, updated PRISMA guidelines were followed to search for pivotal studies and clinical trials published in the last five years. A total of 125 articles discussing locoregional management, radiotherapy, chemotherapy, and immunotherapy strategies were included in our analysis, and salient findings were critically summarized. In addition, an in-depth description of the molecular profile of rGBM and its distinctive characteristics is provided. Finally, we integrate the above-mentioned evidence with the current guidelines published by international societies, including AANS/CNS, EANO, AIOM, and NCCN.

Comparing Tumor Cell Invasion and Myeloid Cell Composition in Compatible Primary and Relapsing Glioblastoma

Simple Summary

We established a new minimally invasive mouse model for GBM relapse. For this, we utilized orthotopical implantation of HSVTK-transduced GBM cells and pharmacological treatment with GCV. In addition, we implanted patient-derived GBM cells of primary or recurrent tumors. We found that recurrent GBM were more aggressively invasive than primary GBM. Moreover, the recurring tumors had a higher ratio of monocyte-derived macrophages among the entire population of tumor associated myeloid cells. This shift in the composition of tumor-associated immune cells appeared to be independent from cell-death signaling or surgical intervention. This model provides the means to investigate the entire process of tumor relapse and test standard as well as experimental therapeutic strategies for relapsing GBM under defined conditions.

Abstract

Glioblastoma (GBM) recurrence after treatment is almost inevitable but addressing this issue with adequate preclinical models has remained challenging. Here, we introduce a GBM mouse model allowing non-invasive and scalable de-bulking of a tumor mass located deeply in the brain, which can be combined with conventional therapeutic approaches. Strong reduction of the GBM volume is achieved after pharmacologically inducing a tumor-specific cell death mechanism. This is followed by GBM re-growth over a predictable timeframe. Pharmacological de-bulking followed by tumor relapse was accomplished with an orthotopic mouse glioma model. Relapsing experimental tumors recapitulated pathological features often observed in recurrent human GBM, like increased invasiveness or altered immune cell composition. Orthotopic implantation of GBM cells originating from biopsies of one patient at initial or follow-up treatment reproduced these findings. Interestingly, relapsing GBM of both models contained a much higher ratio of monocyte-derived macrophages (MDM) versus microglia than primary GBM. This was not altered when combining pharmacological de-bulking with invasive surgery. We interpret that factors released from viable primary GBM cells preferentially attract microglia whereas relapsing tumors preponderantly release chemoattractants for MDM. All in all, this relapse model has the capacity to provide novel insights into clinically highly relevant aspects of GBM treatment.

Transtentorial dissemination of optic nerve glioblastoma: case report

Optic nerve glioblastoma is a rare entity that usually presents with rapidly progressive vision loss, which eventually results in blindness and, ultimately, death. As with malignant gliomas in other anatomical locations, local recurrence is common. Isolated rapid changes in vision, atypical neuroimaging findings, and the rarity of optic nerve glioblastoma may render diagnosis challenging and, thus, delay treatment. The authors present a case of optic nerve glioblastoma that was treated with subtotal resection followed by adjuvant radiation therapy and temozolomide. One year following the initial diagnosis, the patient developed a right cerebellar lesion, which was histopathologically consistent with glioblastoma. This case represents the first report of transtentorial dissemination of an optic nerve glioblastoma. In addition, the authors reviewed the literature regarding optic nerve glioblastomas. Of the 73 previously reported cases of malignant optic nerve gliomas, 32 were histologically confirmed glioblastomas. The mean age at diagnosis was 62 years, and 56% were male; the median survival was 7 months. A malignant glioma of the optic nerve should be considered in the differential diagnosis of a patient with rapidly progressive visual loss. However, the incidence of optic nerve glioblastoma is exceedingly low.

A comprehensive profile of recurrent glioblastoma

In spite of relentless efforts to devise new treatment strategies, primary glioblastomas invariably recur as aggressive, therapy-resistant relapses and patients rapidly succumb to these tumors. Many therapeutic agents are first tested in clinical trials involving recurrent glioblastomas. Remarkably, however, fundamental knowledge on the biology of recurrent glioblastoma is just slowly emerging. Here, we review current knowledge on recurrent glioblastoma and ask whether and how therapies change intra-tumor heterogeneity, molecular traits and growth pattern of glioblastoma, and to which extent this information can be exploited for therapeutic decision-making. We conclude that the ability to characterize and predict therapy-induced changes in recurrent glioblastoma will determine, whether, one day, glioblastoma can be contained in a state of chronic disease.

IDH mutations may not preclude distant, trans-tentorial spread in gliomas: a case report and review of the literature

Background

IDH mutations have been demonstrated to confer prolonged survival in patients suffering from gliomas, but the mechanisms underlying the improved prognosis are unclear. While some studies have attributed these observations to an enhanced sensitivity to genotoxic therapies, others have postulated that IDH-mutated gliomas exhibit less aggressive intrinsic biological behavior, including the propensity to invade distant sites. Although most gliomas recur local to the site of initial presentation, some tumors demonstrate distant recurrence, the vast majority of which involve the contralateral hemisphere. Trans-tentorial spread has been described once before, in which a supratentorial glioblastoma was reported to recur infratentorially in the cerebellum.

Case presentation

We describe a patient who underwent surgical resection, followed by adjuvant radiation and temozolomide of a World Health Organization (WHO) III anaplastic astrocytoma in the right temporal lobe, exhibiting an IDH1 (R132H) mutation. Twenty-two months after surgery, he developed a second lesion, located in the right cerebellum, suspicious for recurrent tumor versus radiation necrosis. A second surgery was performed, and pathology demonstrated recurrent tumor, consistent with IDH1-mutated anaplastic astrocytoma.

Conclusions

This is the first example of trans-tentorial spread in an IDH-mutated glioma, suggesting that despite improved survival, IDH mutations may not preclude gliomas from exhibiting the ability to invade distant sites of the brain.

[Glioblastoma metastases: a literature review and a description of six clinical observations]

INTRODUCTION

since the 1990s, the literature has described cases of glioblastoma metastases with the development of foci located at a distance from the primary tumor. However, the pathogenesis of this process remains unclear until the end. This focus is believed to result, on the one hand, from tumor metastasis from the primary site and, on the other hand, from multifocal growth. This article presents a literature review and a description of clinical observations of patients with glioblastoma metastases.

MATERIAL AND METHODS

The study included 6 patients (1 female and 5 males) with brain glioblastomas who received treatment at the Burdenko Neurosurgical Institute (5 patients) and the Department of Neurosurgery of the Research Center of Neurology (1 patient) in the period from 2010 to 2014. Neurophysiological control was used if the tumor was localized near the eloquent cortical areas and pathways; 4 of 6 patients were operated on using the methods of intraoperative fluorescence diagnosis (5-ALA agent--Alasens).

RESULTS

Four patients had metastases within one hemisphere, two had metastases in the contralateral hemisphere in the period of 5 to 18 months after the first operation. The primary tumor site was located near the ventricular system in two patients. In one patient, the lateral ventricle was opened during the first operation. In another patient, the prepontine cistern was opened during the first operation. In two patients, the primary tumor site was located at a distance from the lateral ventricles, however, the tumor was located near them during recurrence. Based on metabolic navigation, fluorescence of the tumor was observed in the four patients during both the first and repeated operations.

CONCLUSIONS

The close relationship between primary glioblastomas and metastases and the cerebrospinal fluid circulation pathways may confirm the fact of dissemination of tumor cells with cerebrospinal fluid flow. In our opinion, there should be an increased suspicion of the possibility for metastases of glioblastomas that are closely associated with the cerebrospinal fluid circulation pathways. Metabolic navigation with 5-ALA is effective both during primary surgery in patients with glioblastomas and during resection of glioblastoma metastases.

Optimizing glioblastoma temozolomide chemotherapy employing lentiviral-based anti-MGMT shRNA technology

Despite treatments combining surgery, radiation-, and chemotherapy, patients affected by glioblastoma (GBM) have a limited prognosis. Addition of temozolomide (TMZ) to radiation therapy is the standard therapy in clinical application, but effectiveness of TMZ is limited by the tumor's overexpression of the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT). The goal of this study was to use the highly specific and efficient RNA interference (RNAi) pathway to modulate MGMT expression to increase TMZ efficiency in chemotherapy resistant GBM. Using lentiviral-based anti-MGMT small hairpin RNA (shRNA) technology we observed a specific inhibition of the MGMT expression in GBM cell lines as well as in subcutaneous tumors. Tumor growth inhibition was observed following TMZ treatment of xenografts with low MGMT expression in contrast to xenografts with high MGMT expression. Bioluminescence imaging (BLI) measurements indicated that luciferase and shRNA-expressing lentiviruses were able to efficiently transduce the GBM xenografts in vivo. Treatment combining injection of a lentivirus expressing an anti-MGMT shRNA and TMZ induced a reduction of the size of the tumors, in contrast with treatment combining the lentivirus expressing the control shRNA and TMZ. Our data suggest that anti-MGMT shRNA therapy could be used in combination with TMZ chemotherapy in order to improve the treatment of resistant GBM.

Mesenchymal migration as a therapeutic target in glioblastoma

Extensive infiltration of the surrounding healthy brain tissue is a cardinal feature of glioblastomas, highly lethal brain tumors. Deep infiltration by the glioblastoma cells renders complete surgical excision difficult and contemporary adjuvant therapies have had little impact on long-term survival. Thus, deep infiltration and resistance to irradiation and chemotherapy remain a major cause of patient mortality. Modern therapies specifically targeted to this unique aspect of glioblastoma cell biology hold significant promise to substantially improve survival rates for glioblastoma patients. In the present paper, we focus on the role of adhesion signaling molecules and the actin cytoskeleton in the mesenchymal mode of motility that characterizes invading glioblastoma cells. We then review current approaches to targeting these elements of the glioblastoma cell migration machinery and discuss other aspects of cell migration that may improve the treatment of infiltrating glioblastoma.

Tumour control by whole brain irradiation of anti-VEGF-treated mice bearing intracerebral glioma

AIM OF THE STUDY

Tumour angiogenesis and invasion are key features of glioblastoma multiforme (GBM). Angiogenesis inhibitors increase progression-free survival (PFS) of recurrent GBM patients. VEGF inhibition controls the bulk tumour growth by inhibition of angiogenesis, but does not inhibit the invasive tumour component. We investigated if invasive tumour growth can be controlled by combining anti-VEGF treatment with irradiation of tumour plus surrounding brain in an orthotopic murine model for GBM.

METHODS AND MATERIALS

GBM cell line U251-NG2 was inoculated through a guide screw in the right frontal lobe of 53 athymic nude mice. Pegaptanib (a slow-releasing aptamer against VEGF) was injected in the tumour bed either or not followed by irradiation treatment with implanted I-125 seeds. Pegaptanib and/or irradiation were compared with sham-treated controls, resulting in four groups of 10-15 mice each. After 6 weeks of treatment, histological analysis was performed on all brains.

RESULTS

VEGF inhibition by locally deposited pegaptanib decreased tumour blood vessel density, and increased tumour hypoxia. Pegaptanib treatment still allowed the formation of tumour satellites. Irradiation decreased tumour size and suppressed formation of satellites. Combined pegaptanib plus irradiation further increased PFS. Tumour size directly correlated with PFS.

CONCLUDING STATEMENT

The anti-tumour effects of local VEGF inhibition are partially circumvented by the formation of invasive tumour satellites. Additional irradiation is effective in slowing down proliferation of these invasive tumour components.

Differential radiosensitizing potential of temozolomide in MGMT promoter methylated glioblastoma multiforme cell lines

PURPOSE

To investigate the radiosensitizing potential of temozolomide (TMZ) for human glioblastoma multiforme (GBM) cell lines using single-dose and fractionated gamma-irradiation.

METHODS AND MATERIALS

Three genetically characterized human GBM cell lines (AMC-3046, VU-109, and VU-122) were exposed to various single (0-6 Gy) and daily fractionated doses (2 Gy per fraction) of gamma-irradiation. Repeated TMZ doses were given before and concurrent with irradiation treatment. Immediately plated clonogenic cell-survival curves were determined for both the single-dose and the fractionated irradiation experiments. To establish the net effect of clonogenic cell survival and cell proliferation, growth curves were determined, expressed as the number of surviving cells.

RESULTS

All three cell lines showed MGMT promoter methylation, lacked MGMT protein expression, and were sensitive to TMZ. The isotoxic TMZ concentrations used were in a clinically feasible range of 10 micromol/L (AMC-3046), 3 micromol/L (VU-109), and 2.5 micromol/L (VU-122). Temozolomide was able to radiosensitize two cell lines (AMC 3046 and VU-122) using single-dose irradiation. A reduction in the number of surviving cells after treatment with the combination of TMZ and fractionated irradiation was seen in all three cell lines, but only AMC 3046 showed a radiosensitizing effect.

CONCLUSIONS

This study on TMZ-sensitive GBM cell lines shows that TMZ can act as a radiosensitizer and is at least additive to gamma-irradiation. Enhancement of the radiation response by TMZ seems to be independent of the epigenetically silenced MGMT gene.