Can we rely on synthetic pharmacotherapy for the treatment of glioblastoma?

Introduction: Despite decades of clinical trials utilizing conventional and novel therapeutics, the effective treatment of glioblastoma remains one of the most formidable challenges in oncology. Current standard of care includes surgery and chemoradiation. Synthetic pharmacotherapies continue to be explored as potential therapeutic options for glioblastoma patients.Areas covered: This study reviews synthetic pharmacotherapies that are currently under investigation in phase I-III clinical trials. The authors of this study highlight the mechanisms of action of the synthetic pharmacotherapy agents under investigation, outline the available evidence for their utility based on the literature, and summarize the current landscape.Expert opinion: Although warranting further investigation, the studies generally highlighted here have not shown remarkable changes in clinical benefits beyond what has already been established with radiochemotherapy. As we develop more synthetics, we will likely need to combine them with other synthetics to target multiple separate molecular pathways. There is considerable potential when this treatment strategy is guided by molecular profiling approaches which seek to stratify patients based on treatments that would be most efficacious for them.

Current FDA-Approved Therapies for High-Grade Malignant Gliomas

The standard of care (SOC) for high-grade gliomas (HGG) is maximally safe surgical resection, followed by concurrent radiation therapy (RT) and temozolomide (TMZ) for 6 weeks, then adjuvant TMZ for 6 months. Before this SOC was established, glioblastoma (GBM) patients typically lived for less than one year after diagnosis, and no adjuvant chemotherapy had demonstrated significant survival benefits compared with radiation alone. In 2005, the Stupp et al. randomized controlled trial (RCT) on newly diagnosed GBM patients concluded that RT plus TMZ compared to RT alone significantly improved overall survival (OS) (14.6 vs. 12.1 months) and progression-free survival (PFS) at 6 months (PFS6) (53.9% vs. 36.4%). Outside of TMZ, there are four drugs and one device FDA-approved for the treatment of HGGs: lomustine, intravenous carmustine, carmustine wafer implants, bevacizumab (BVZ), and tumor treatment fields (TTFields). These treatments are now mainly used to treat recurrent HGGs and symptoms. TTFields is the only treatment that has been shown to improve OS (20.5 vs. 15.6 months) and PFS6 (56% vs. 37%) in comparison to the current SOC. TTFields is the newest addition to this list of FDA-approved treatments, but has not been universally accepted yet as part of SOC.

Feasibility and Value of Telemedicine Neurosurgical Consultations in a Rural Health System

INTRODUCTION

Telemedicine has been available for more than 20 years and is playing an increasing role in clinical care. However, few studies have evaluated the value of telemedicine in neurosurgical consultations and in guiding neurosurgical care.

METHODS

In this prospective observational study, we examined our experience with emergency video telemedicine consultations for neurosurgical patients at a rural hospital system. Our system uses secure and HIPAA-compliant video conferencing to connect providers and patients to a remote neurosurgery consultant, and operates one out of two days.

RESULTS

During a ten-month period, 229 neurosurgical telemedicine consultations were performed. Two-thirds of the patients had intracranial pathology, 28% had spinal pathology and 3% of the consults were for patients who returned after care at our institution or required clearance for another procedure. Five patients required transfer within the hospital system and 12 out of the hospital system for a higher level of care (total 7.4%). Patients that required transfer most frequently had intracranial pathology (70%). The number of patients transferred out was less than in the year before telemedicine was available.

CONCLUSION

Telemedicine consultation for neurosurgery is feasible for a variety of neurosurgical pathologies, improves patient access to neurosurgery expertise, and facilitates appropriate transfers to a higher level of care when required. Our findings are especially relevant in light of the COVID-19 pandemic, which has highlighted the importance of delivering quality medical care when physical patient contact is not possible.

DNX-2401: an investigational drug for the treatment of recurrent glioblastoma

Introduction: High-grade gliomas (HGG) are extremely aggressive brain malignancies that are fatal. Despite maximal resection, chemotherapy, and radiation, these tumors inevitably recur and present a poor median overall survival (mOS); hence a pressing need for improved treatments.Areas covered: This review assesses DNX-2401 as a treatment of recurrent HGG. Phase I data on efficacy, safety, and tolerability are examined while insights and perspectives on future directions are offered.Expert opinion: This phase I study assessed DNX-2401 in two study groups; one received an intratumoral injection without tumor resection while the second received an intratumoral injection followed by surgical resection 14 days later with a second injection into the resection cavity. In patients that did not receive resection, the mOS was 9.5 months while patients in the resection group had a mOS of 13 months, a promising extension of survival compared to historical controls. Furthermore, this study had numerous long-term survivors living for greater than 2 years. DNX-2401 was well tolerated with no Grade 3/4 adverse events; it provoked an immunologic response to the tumor which may contribute to the complete responses in some patients. Randomized-control trials are necessary and further studies are warranted to identify patients who will benefit most.

Targeted radiotherapy for malignant gliomas

Malignant glioma remains a disease with poor prognosis despite recent advances in the multidisciplinary care of this disease. Herein we review the evolution of and recent advances in radiation therapy for malignant glioma that have allowed for more targeted therapy, potentially improving efficacy while decreasing normal tissue toxicity. Current and emerging techniques are presented, including stereotactic radiotherapy and radiosurgery, brachytherapy, radioimmunotherapy, and charged particle therapy, as well as the combination of these modalities with novel targeted biochemotherapies.

Stopping cancer in its tracks: using small molecular inhibitors to target glioblastoma migrating cells

Glioblastoma multiforme (GBM) represents one of the most common aggressive types of primary brain tumors. Despite advances in surgical resection, novel neuroimaging procedures, and the most recent adjuvant radiotherapy and chemotherapy, the median survival after diagnosis is about 12-14 months. Targeting migrating GBM cells is a key research strategy in the fight against this devastating cancer. Though the vast majority of the primary tumor focus can be surgically resected, these migrating cells are responsible for its universal recurrence. Numerous strategies and technologies are being explored to target migrating glioma cells, with small molecular inhibitors as one of the most commonly studied. Small molecule inhibitors, such as protein kinase inhibitors, phosphorylation site inhibitors, protease inhibitors, and antisense oligonucleotides show promise in slowing the progression of this disease. A better understanding of these small molecule inhibitors and how they target various extra- and intracellular signaling pathways may eventually lead to a cure for GBM.

OTX2 is critical for the maintenance and progression of Shh-independent medulloblastomas

OTX2 is a developmentally regulated transcription factor involved in early morphogenesis of the central nervous system. This gene is amplified and overexpressed in medulloblastoma cell lines, but the nature and extent of its genetic alterations in primary tumors have not been evaluated. Analysis of a large cohort of primary medulloblastomas revealed frequent focal copy number gain of a region minimally containing OTX2 as a single gene. OTX2 copy number gain was restricted to tumor subtypes that did not express a molecular signature of Wnt or Shh pathway activation. FISH analysis revealed copy number gain in a subset of cells within medulloblastoma samples, suggesting a late event in tumor progression. Gain of OTX2 copy number was associated with the presence of anaplastic histologic features and shorter survival in medulloblastoma patients. In support of a functional role, ectopic OTX2 expression enhanced proliferation and tumorigenicity of immortalized primary cells, whereas OTX2 knockdown in medulloblastoma cells prolonged the survival of animals bearing xenograft tumors. Mechanistic investigations revealed upregulation of MYC as a potential mechanism whereby OTX2 promotes tumor progression. Our findings define OTX2 as an important oncogenic driver in medulloblastoma.

Upward transtentorial herniation, hydrocephalus, and cerebellar edema in hypertensive encephalopathy

BACKGROUND

Edema of the cerebellum with secondary obstructive hydrocephalus is a rare presentation of hypertensive encephalopathy. The authors report an unusual case of isolated posterior fossa swelling with upward transtentorial herniation and hydrocephalus causing neurologic deterioration. These patients are often initially evaluated by a neurologist because of the acute neurologic symptoms. Prompt diagnosis with aggressive blood pressure control may obviate the need for emergent cerebrospinal fluid (CSF) diversion.

REVIEW SUMMARY

This is a case report of a 26-year-old man who presented to the emergency room with confusion and somnolence over a 2-day period. His initial blood pressure was 175/110 mmHg. On examination he was disoriented, with a Glasgow Coma Scale score of 12 points, opening his eyes only to loud verbal stimuli, verbalizing inappropriately, and he was only able to follow simple commands. Neuroimaging revealed edema of the cerebellar folia with noncommunicating hydrocephalus and upward transtentorial herniation. Differential diagnoses of posterior fossa tumor, rhombencephalitis, and hypertensive encephalopathy were entertained. A thorough literature review is included with the discussion of this case. The patient underwent emergent ventriculostomy for CSF drainage and prompt blood pressure control with nitroprusside. After 48 hours of CSF drainage and correction of his hypertension, his neurologic examination normalized. Repeat imaging revealed near resolution of the obstructive hydrocephalus and cerebellar edema.

CONCLUSION

Isolated edema of the cerebellum with upward transtentorial herniation and obstructive hydrocephalus is a rare presentation of hypertensive encephalopathy and should be considered in patients with an acute hypertensive crisis and mental status changes. This entity responds to prompt blood pressure control; however, emergent ventriculostomy by a neurosurgical team should be entertained for neurologic deterioration secondary to significant obstructive hydrocephalus, as illustrated in this case.

Identification of OTX2 as a Medulloblastoma Oncogene Whose Product can be Targeted by All-Trans Retinoic Acid

Through digital karyotyping of permanent medulloblastoma cell lines, we found that the homeobox gene OTX2 was amplified more than 10-fold in three cell lines. Gene expression analyses showed that OTX2 transcripts were present at high levels in 14 of 15 (93%) medulloblastomas with anaplastic histopathologic features. Knockdown of OTX2 expression by siRNAs inhibited medulloblastoma cell growth in vitro, whereas pharmacologic doses of all-trans retinoic acid repressed OTX2 expression and induced apoptosis only in medulloblastoma cell lines that expressed OTX2. These observations suggest that OTX2 is essential for the pathogenesis of anaplastic medulloblastomas and that these tumors may be amenable to therapy with all-trans-retinoic acid.

Identification of OTX2 as a medulloblastoma oncogene whose product can be targeted by all-trans retinoic acid

Through digital karyotyping of permanent medulloblastoma cell lines, we found that the homeobox gene OTX2 was amplified more than 10-fold in three cell lines. Gene expression analyses showed that OTX2 transcripts were present at high levels in 14 of 15 (93%) medulloblastomas with anaplastic histopathologic features. Knockdown of OTX2 expression by siRNAs inhibited medulloblastoma cell growth in vitro, whereas pharmacologic doses of all-trans retinoic acid repressed OTX2 expression and induced apoptosis only in medulloblastoma cell lines that expressed OTX2. These observations suggest that OTX2 is essential for the pathogenesis of anaplastic medulloblastomas and that these tumors may be amenable to therapy with all-trans-retinoic acid.

Malignant peripheral nerve sheath tumor of the spine after radiation therapy for Hodgkin's lymphoma

We report the development of a malignant peripheral nerve sheath tumor (MPNST) in 2 patients after irradiation for Hodgkin's lymphoma. Clinicians should be aware of this uncommon, but important fatal complication of radiation therapy. The first case is a 37-year-old man who was diagnosed with nodular sclerosing (NS) Hodgkin's lymphoma and underwent successful mantle radiation. He presented to our neurosurgery service with a left C6 radiculopathy 6 years later. The second case is a 30-year-old female diagnosed with NS Hodgkin's lymphoma. She did well with extensive radiotherapy until 5 years later when she developed severe right arm and chest pain secondary to recurrent lymphoma. After aggressive radio- and chemotherapy, she presented to the neurosurgery service with a right Horner's syndrome, right C6 radiculopathy, and weakness of her right triceps and wrist extensors. Both patients obtained magnetic resonance imaging revealing intradural extramedullary cervical nerve root associated mass lesions. Two years after radiation therapy for his Hodgkin's lymphoma, the first patient underwent a C6 laminectomy at an outside institution for resection of a benign neurofibroma. Four years later, he underwent a posterior C5-7 laminectomy with lateral mass plate fusion and partial excision of a recurrent mass diagnosed as a MPNST. The second patient underwent a C5-6 hemilaminectomy and partial resection of a tumor also pathologically consistent with MPNST. We present 2 case reports of patients who developed neurofibrosarcomatous tumors with malignant transformation after undergoing radiation therapy for Hodgkin's lymphoma. Despite prompt surgical resection, these tumors exhibited aggressive behavior. Numerous cases of soft tissue tumors have been described to arise in areas of prior radiation therapy; however, there have been rare reports of de novo MPNST after radiation therapy, especially in the setting of Hodgkin's lymphoma. Postirradiation MPNST should be considered in the differential diagnosis of a painful, enlarging mass in a previously irradiated area.

Spontaneous cervical epidural hematoma: case report and literature review

BACKGROUND

Spontaneously occurring epidural hematomas for which no etiology is identified are rare phenomenon. These are often neurosurgical emergencies; therefore, prompt diagnosis and treatment are paramount. Because of the rarity of this condition, we have illustrated in this recent case its presentation, evaluation and management.

METHODS

A 63-year-old male presented to our emergency room with right-sided hemiparesis and contralateral hypesthesia, consistent with a C5 Brown-Séquard syndrome. An initial evaluation for cerebral infarction was unremarkable, including a negative brain magnetic resonance image. Further imaging revealed a cervical epidural hematoma of unknown etiology.

RESULTS

The patient underwent emergent laminectomy for decompression and evacuation of the hematoma within 24 hours of his presentation to the emergency room. The patient's symptoms improved remarkably after surgery and a 4-month follow-up imaging evaluation revealed no recurrence of his hematoma.

CONCLUSION

This report highlights the various presentations, evaluation, and management options for this rare diagnosis. It emphasizes the necessity of prompt diagnosis for possible emergent intervention.

Astroglia Induce Cytotoxic Effects on Brain Tumors via a Nitric Oxide-Dependent Pathway Both in Vitro and in Vivo

OBJECTIVE

In the central nervous system, astroglia produce nitric oxide (NO) in response to cytokines. We investigated whether cytokine stimulation of astroglia could inhibit brain tumor cell growth in vitro and prolong survival in vivo via an NO-dependent pathway.

METHODS

Astroglia cultures were stimulated with the cytokines lipopolysaccharide and interferon-gamma and subsequently seeded with tumor cell lines. Wild-type mice and inducible NO synthase-knockout mice received in vivo cytokine stimulation followed by B16F10 murine melanoma challenge.

RESULTS

Our in vitro studies demonstrate that astroglia stimulated to produce NO by the addition of cytokines dose-dependently inhibit the growth of one primary rat brain tumor cell line (9L) and three primary human brain tumor cell lines (H80, U87, and U373). This inhibition of tumor cell growth is also observed in metastatic cell lines (B16F10 melanoma, Lewis lung carcinoma, and CT26 colon). Cultured astrocytes from inducible NO synthase-knockout mice, which are incapable of induction of NO, are without the enhanced tumoricidal effect. Furthermore, when C57BL/6 mice are primed to produce NO through stereotactic intracranial administration of lipopolysaccharide plus interferon-gamma and subsequently challenged with B16F10 murine melanoma, survival is significantly prolonged, with a median survival of 26 days versus 16 days in the control group (P < 0.001). The addition of an NO synthase inhibitor (N(G)-nitro-l-arginine methyl ester) decreases this beneficial effect (median survival, 21 d).

CONCLUSION

These findings suggest that NO may have an important role as a defense mechanism molecule against brain tumors; stimulation or modification of this mechanism may represent a new approach to the treatment of primary and metastatic brain tumors.

Rate and severity of HIV-associated dementia (HAD): correlations with Gp41 and iNOS

BACKGROUND

Fifteen to thirty percent of AIDS patients develop some type of neurologic disorder during the course of their illness and the vast majority of these neurologic disorders will be HIV-associated dementia (HAD). These patients can exhibit varying degrees of severity and rates of progression of HAD. Neuropathologic variables that are associated with the rate of progression of HAD are not known.

MATERIALS AND METHODS

Tissue was collected at autopsy from the Johns Hopkins University HIV Neurology Program. Seventy-one AIDS patients of this prospectively characterized population were followed until death to obtain information on dementia severity and the rate of neurological progression. Immunoblot analysis of immunological nitric oxide synthase (iNOS), HAM56, gp41, p24, gp120, and beta-tubulin was performed and the levels of iNOS, HAM56, gp41, and p24 were normalized to beta-tubulin and analyzed for significance by means of the Kruskal-Wallis test for multiple groups.

RESULTS

We have identified unique groups within this spectrum and designated them slow, moderate, and rapid progressors. Slow and moderate progressors' neurological progression occurs over a course of months to years, whereas the rapid progressors' disease shows rapid increases in severity over weeks to months. In the present study we demonstrate that the severity and rate of progression of HAD correlates significantly with levels of the HIV-1 coat protein, gp41, iNOS, and HAM56, a marker of microglial/macrophage activation.

CONCLUSION

The severity and rate of progression of HAD correlates with indices of immune activation as well as levels of iNOS and gp41. There appears to be a threshold effect in which high levels of gp41, iNOS, and immune activation are particularly associated with severe (Memorial Sloan-Kettering score 3 to 4) and rapidly progressive HAD.

Mechanisms and structural determinants of HIV-1 coat protein, gp41-induced neurotoxicity

Of the individuals with human immunodeficiency virus type 1 (HIV-1) infection, 20-30% will develop the neurological complication of HIV-associated dementia (HAD). The mechanisms underlying HAD are unknown; however, indirect immunologically mediated mechanisms are theorized to play a role. Recently, the HIV-1 coat protein gp41 has been implicated as a major mediator of HAD through induction of neurocytokines and subsequent neuronal cell death. Using primary mixed cortical cultures from neuronal nitric oxide synthase (NOS) null (nNOS-/-) mice and immunological NOS null (iNOS-/-) mice, we establish iNOS-derived NO as a major mediator of gp41 neurotoxicity. Neurotoxicity elicited by gp41 is markedly attenuated in iNOS-/- cultures compared with wild-type and nNOS-/- cultures. The NOS inhibitor L-nitroarginine methyl ester is neuroprotective in wild-type and nNOS-/- cultures, confirming the role of iNOS-derived NO in gp41 neurotoxicity. Confirming that iNOS-/- cultures lack iNOS, gp41 did not induce iNOS in iNOS-/- cultures, but it markedly induced iNOS in wild-type and nNOS-/- cultures. We elucidate the region of gp41 that is critical for iNOS induction and neuronal cell death by monitoring iNOS induction with overlapping peptides spanning gp41. We show that the N-terminal region of gp41, which we designate as the neurotoxic domain, induces iNOS protein activity and iNOS-dependent neurotoxicity at picomolar concentrations in a manner similar to recombinant gp41 protein. Our experiments suggest that gp41 is eliciting the induction of iNOS through potential cell surface receptors or binding sites because the induction of iNOS is dose dependent and saturable and occurs at physiologically relevant concentrations. These data confirm that the induction of iNOS by gp41 and the production of NO are primary mediators of neuronal damage and identify a neurotoxic domain of gp41 that may play an important role in HAD.

Immunologic NO synthase: elevation in severe AIDS dementia and induction by HIV-1 gp41

Indirect mechanisms are implicated in the pathogenesis of the dementia associated with human immunodeficiency virus-type 1 (HIV-1) infection. Proinflammatory molecules such as tumor necrosis factor alpha and eicosanoids are elevated in the central nervous system of patients with HIV-1-related dementia. Nitric oxide (NO) is a potential mediator of neuronal injury, because cytokines may activate the immunologic (type II) isoform of NO synthase (iNOS). The levels of iNOS in severe HIV-1-associated dementia coincided with increased expression of the HIV-1 coat protein gp41. Furthermore, gp41 induced iNOS in primary cultures of mixed rat neuronal and glial cells and killed neurons through a NO-dependent mechanism. Thus, gp41-induced NO formation may contribute to the severe cognitive dysfunction associated with HIV-1 infection.

Neurovirulent simian immunodeficiency virus infection induces neuronal, endothelial, and glial apoptosis

BACKGROUND

Studies of human immunodeficiency virus type 1 (HIV-1) associated dementia have shown neuronal loss in discrete areas. The presence and mechanism of neuronal death, however, has remained quite elusive. One mechanism of cell death, apoptosis, has been clearly demonstrated outside the central nervous system (CNS) in HIV-1 infection but has not been firmly established within the CNS. Therefore, we set out to ascertain whether neuronal cell loss in simian immunodeficiency virus (SIV) encephalitis, an animal model of HIV-1-associated dementia, is a result of apoptosis.

MATERIALS AND METHODS

With the aid of an in situ technique for identifying the 3'-OH ends of newly fragmented DNA characteristic of apoptosis, in conjunction with specific detected morphological criteria via light microscopy, we have examined encephalitic and nonencephalitic brains of macaques infected with a neurovirulent, neuroendotheliotropic strain of SIV to see if virus is spatially associated with apoptosis of neurons and non-neuronal cell types.

RESULTS

We demonstrate the presence of DNA damage, indicative of apoptosis, in neurons, endothelial cells, and glial cells of the CNS of SIV-infected macaques. Furthermore, we observe an association between the localization of cells with significant DNA fragmentation and perivascular inflammatory cell infiltrates containing SIV-infected macrophages and multinucleated giant cells. Quantitative analysis reveals significantly more cells with DNA fragmentation in the CNS of macaques infected with neurovirulent, neuroendotheliotropic SIV strains as compared with strictly lymphocyte-tropic SIV strains and SIV negative controls.

CONCLUSIONS

Our findings of apoptosis in SIV-infected CNS may potentially lead to a better understanding of the AIDS dementia complex, ultimately providing a basis for better treatments.