Isolation and characterization of stem cells from human central nervous system malignancies.

Central Nervous System (CNS) tumors include some of the most invasive and lethal tumors in humans. The poor prognosis in patients with CNS tumors is ascribed to their invasive nature. After the description of a stem cell-like cohort in hematopoietic cancers, tumor stem cells (TSCs) have been isolated from a variety of solid tumors, including brain tumors. Further research has uncovered the crucial role these cells play in the initiation and propagation of brain tumors. More importantly, TSCs have also been shown to be relatively resistant to conventional cytotoxic therapeutics, which may also account for the alarmingly high rate of CNS tumor recurrence. In order to elucidate prospective therapeutic targets it is imperative to study these cells in detail and to accomplish this, we need to be able to reliably isolate and characterize these cells. This chapter will therefore, provide an overview of the methods used to isolate and characterize stem cells from human CNS malignancies.

Laboratory models for central nervous system tumor stem cell research.

Central nervous system (CNS) tumors are complex organ systems comprising of a neoplastic component with associated vasculature, inflammatory cells, and reactive cellular and extracellular components. Research has identified a subset of cells in CNS tumors that portray defining properties of neural stem cells, namely, that of self-renewal and multi-potency. Growing evidence suggests that these tumor stem cells (TSC) play an important role in the maintenance and growth of the tumor. Furthermore, these cells have also been shown to be refractory to conventional therapy and may be crucial for tumor recurrence and metastasis. Current investigations are focusing on isolating these TSC from CNS tumors to investigate their unique biological processes. This understanding will help identify and develop more effective and comprehensive treatment strategies. This chapter provides an overview of some of the most commonly used laboratory models for CNSTSC research.

Emerging strategies for the treatment of tumor stem cells in central nervous system malignancies.

High-grade central nervous system (CNS) tumors are notorious for high rates of recurrence and poor outcomes. A small cohort of tumor cells, dubbed tumor stem cells (TSC), are now being recognized as an important subset of the tumor that is resistant to chemotherapy and radiotherapy and account for the high recurrence rates. Recent research is developing modalities to target TSCs specifically in a bid to improve the response of the tumor as a whole. The methods being employed to target TSCs include targeting TSC-specific pathways or receptors, TSC-sensitizing agents to chemotherapy and radiotherapy, immunotherapy, TSC-differentiating agents, and viral therapy. This chapter provides an overview of strategies that are expected to help develop new and more effective treatments for CNS tumors.

Targeting glioblastoma cancer stem cells: the next great hope?

Glioblastoma multiforme (GBM) is the most common primary brain tumor and is notorious for its poor prognosis. The highly invasive nature of GBM and its inherent resistance to therapy lead to very high rates of recurrence. Recently, a small cohort of tumor cells, called cancer stem cells (CSCs), has been recognized as a subset of tumor cells with self-renewal ability and multilineage capacity. These properties, along with the remarkable tumorigenicity of CSCs, are thought to account for the high rates of tumor recurrence after treatment. Recent research has been geared toward understanding the unique biological characteristics of CSCs to enable development of targeted therapy. Strategies include inhibition of CSC-specific pathways and receptors; agents that increase sensitivity of CSCs to chemotherapy and radiotherapy; CSC differentiation agents; and CSC-specific immunotherapy, virotherapy, and gene therapy. These approaches could inform the development of newer therapeutics for GBM.

The role of the CXCR4 cell surface chemokine receptor in glioma biology.

CXCR4, a cell surface chemokine receptor, mediates cellular dissemination, invasion, and proliferation in a wide range of cancers including gliomas. It is over-expressed in glioma progenitor cells, and its protein ligand, CXCL12, has been shown to mediate a specific proliferative response in these cells thereby implicating a role for CXCR4 in glioma initiation and renewal. Given the failure of currently employed therapies to meaningfully impact prognosis in patients with high-grade gliomas, the CXCR4-CXCL12 axis represents a novel biologically relevant mechanism that could be specifically targeted for therapy. From this perspective, this review summarizes the biological effects of CXCR4 activity and its implications for glioma pathogenesis. Ultimately, the development of effective treatment approaches for malignant glioma must be based on a rational mechanistic understanding of tumor cell biology. As such, this article presents such a framework with regard to the CXCR4 pathway in glioma thereby supporting the further investigation of CXCR4 as a therapeutic target in patients with this disease.

Integrating spatially resolved three-dimensional MALDI IMS with in vivo magnetic resonance imaging.

We have developed a method for integrating three dimensional-volume reconstructions of spatially resolved matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) ion images of whole mouse heads with high-resolution images from other modalities in an animal-specific manner. This approach enabled us to analyze proteomic profiles from MALDI IMS data with corresponding in vivo data provided by magnetic resonance imaging.

Stem cells as vehicles for the treatment of brain cancer.

Stem cell therapy represents a promising new therapeutic modality for infiltrative gliomas. The promise of this emerging technology centers on the potent migratory tropism exhibited by stem cells for disseminated foci of intracranial pathologic findings. This important characteristic, which has been validated in a wide set of preclinical studies, forms a foundation for the use of transplanted stem cell populations as vehicles for the delivery of tumor-toxic molecules to sites of intracranial tumor. Nevertheless, although experimental models using this technique to target brain tumors have shown encouraging results, many concerns and questions remain to be addressed before realistic clinical implementation of this strategy can begin. Key among these are an inadequate understanding of the specific tropic mechanisms that govern stem cell migration toward invasive tumors and the need to identify appropriate tissue sources and culture processes for the generation of adequate therapeutic stem cell populations. Despite these limitations, the use of stem cells as vectors for the treatment of brain tumors holds significant promise and may prove to be an important therapeutic modality for patients with malignant glioma.

The use of interleukin 12-secreting neural stem cells for the treatment of intracranial glioma.

Neural stem cells (NSCs) are capable of tracking migrating glioma cells. To exploit this tropism to generate an antitumor T-cell response, particularly against disseminating tumor pockets, we inoculated intracranial glioma-bearing mice with interleukin 12 (IL-12) producing NSCs. Intratumoral therapy with IL-12-secreting NSCs prolonged survival compared to treatment with nonsecretory NSCs or saline. NSCs demonstrated strong tropism for disseminating glioma, and IL-12-secreting NSC therapy was associated with enhanced T-cell infiltration in tumor microsatellites and long-term antitumor immunity. These results indicate that the use of tumor tracking NSCs represents a potent new therapeutic modality for glioma.

Induction of glioblastoma apoptosis using neural stem cell-mediated delivery of tumor necrosis factor-related apoptosis-inducing ligand.

Current therapies for gliomas fail to address their highly infiltrative nature. Standard treatments often leave behind microscopic neoplastic reservoirs, resulting in eventual tumor recurrence. Neural stem cells (NSCs) are capable of tracking disseminating glioma cells. To exploit this tropism to develop a therapeutic strategy that targeted tumor satellites, we inoculated human glioblastoma xenografts with tumor necrosis factor-related apoptosis-inducing ligand-secreting NSCs. This resulted in the dramatic induction of apoptosis in treated tumors and tumor satellites and was associated with significant inhibition of tumor growth. These results add credence to the potential of NSCs as therapeutically effective delivery vehicles for the treatment of intracranial glioma.

Intraarterial administration of norcantharidin attenuates ischemic stroke damage in rodents when given at the time of reperfusion: novel uses of endovascular capabilities.

OBJECT Matrix metalloprotease-9 (MMP-9) plays a critical role in infarct progression, blood-brain barrier (BBB) disruption, and vasogenic edema. While systemic administration of MMP-9 inhibitors has shown neuroprotective promise in ischemic stroke, there has been little effort to incorporate these drugs into endovascular modalities. By modifying the rodent middle cerebral artery occlusion (MCAO) model to allow local intraarterial delivery of drugs, one has the ability to mimic endovascular delivery of therapeutics. Using this model, the authors sought to maximize the protective potential of MMP-9 inhibition by intraarterial administration of an MMP-9 inhibitor, norcantharidin (NCTD). METHODS Spontaneously hypertensive rats were subjected to 90-minute MCAO followed immediately by local intraarterial administration of NCTD. The rats' neurobehavioral performances were scored according to the ladder rung walking test results and the Garcia neurological test for as long as 7 days after stroke. MRI was also conducted 24 hours after the stroke to assess infarct volume and BBB disruption. At the end of the experimental protocol, rat brains were used for active MMP-9 immunohistochemical analysis to assess the degree of MMP-9 inhibition. RESULTS NCTD-treated rats showed significantly better neurobehavioral scores for all days tested. MR images also depicted significantly decreased infarct volumes and BBB disruption 24 hours after stroke. Inhibition of MMP-9 expression in the ischemic region was depicted on immunohistochemical analysis, wherein treated rats showed decreased active MMP-9 staining compared with controls. CONCLUSIONS Intraarterial NCTD significantly improved outcome when administered at the time of reperfusion in a spontaneously hypertensive rat stroke model. This study suggests that supplementing endovascular revascularization with local neuroprotective drug therapy may be a viable therapeutic strategy.

Stem cell therapies for malignant glioma.

The prognosis for patients with malignant glioma, which is the most common primary intracranial neoplasm, remains dismal despite significant progress in neurooncological therapies and technology. This is largely due to the inability of current treatment strategies to address the highly invasive nature of this disease. Malignant glial cells often disseminate throughout the brain, making it exceedingly difficult to target and treat all intracranial neoplastic foci, with the result that tumor recurrence is inevitable despite aggressive surgery and adjuvant radiotherapy and/or chemotherapy. The use of neural stem cells (NSCs) as delivery vehicles for tumor-toxic molecules represents the first experimental strategy aimed specifically at targeting disseminated tumor pockets. Investigators have demonstrated that NSCs possess robust tropism for infiltrating tumor cells, and that they can be used to deliver therapeutic agents directly to tumor satellites, with significant therapeutic benefit. With the aim of developing these findings into a clinically viable technology that would not be hindered by ethical and tissue rejection-related concerns, the use of adult tissue-derived stem cells has recently been explored. These technologies represent important progress in the development of a treatment strategy that can specifically target disseminated neoplastic pockets within the brain. Despite encouraging results in preclinical models, however, there are significant impediments that must be overcome prior to clinical implementation of this strategy. Key among these are an inadequate understanding of the specific tropic mechanisms that govern NSC migration toward invasive tumor, and the need to refine the processes used to generate tumor-tropic stem cells from adult tissues so that this can be accomplished in a clinically practicable fashion. Despite these limitations, the use of stem cell therapies for brain tumors holds significant promise and may emerge as an important therapeutic modality for patients with malignant glioma.

Glioma tropic neural stem cells consist of astrocytic precursors and their migratory capacity is mediated by CXCR4.

Malignant gliomas spawn disseminated microsatellites, which are largely refractory to currently employed therapies, resulting in eventual tumor recurrence and death. The use of tumor-tropic neural stem cells (NSCs) as delivery vehicles for therapeutic gene products represents an attractive strategy specifically focused at treating these residual neoplastic foci. We wished to elucidate the biological cues governing NSC tropism for glioma. In this context, we describe that tumor-tropic NSCs comprise largely of astrocytic progenitors expressing chemokine receptor 4 (CXCR4). Blocking of CXCR4 significantly inhibits NSC migration toward the tumor. These findings define specific characteristics associated with the cell populations within transplanted NSCs that demonstrate glioma-tracking behavior.

Treatment of intracranial glioma with in situ interferon-gamma and tumor necrosis factor-alpha gene transfer.

Interferon-gamma (IFNgamma) and tumor necrosis factor-alpha (TNFalpha) are potent immunostimulatory cytokines with demonstrated tumoricidal effects in a variety of cancers. With the aim of investigating their ability to generate antitumor immune responses in malignant brain tumors, we describe the use of in situ adenoviral-mediated IFNgamma and TNFalpha gene transfer in glioma-bearing rodents. Survival was prolonged in mice treated with AdmIFNgamma or AdTNFalpha compared to AdLacZ- and saline-inoculated controls, and AdmIFNgamma- or AdTNFalpha-treated animals revealed significantly smaller tumors. These effects were accompanied by significant up-regulation of tumor MHC-I expression in AdmIFNgamma-inoculated animals, and of MHC-II in AdTNFalpha-treated tumors. Significantly enhanced intratumoral infiltration with CD4(+) and CD8(+) T cells was visible in animals treated with AdmIFNgamma, AdTNFalpha, or a combination of AdmIFNgamma and AdTNFalpha. In addition, AdTNFalpha therapy down-regulated the expression of endothelial Fas ligand, a cell membrane protein implicated as a contributor to immune privilege in cancer. These findings demonstrate the effectiveness of local IFNgamma and TNFalpha gene transfer as a treatment strategy for glioma and illustrate possible physiological pathways responsible for the therapeutic benefit observed.

In situ adenoviral interleukin 12 gene transfer confers potent and long-lasting cytotoxic immunity in glioma.

Interleukin 12 (IL-12) isa cytokine that promotesan antitumor Th1-type pattern of differentiation in mature naïveT cells. Despite its therapeutic success in multiple animal models of cancer, the utility of systemically administered recombinant cytokine has been limited by its toxicity. This has encouraged the development of local IL-12 delivery systems through gene transfer. To determine the effect of local adenoviral delivery of IL- 12 on glioma immunogenicity, mice bearing GL-26 gliomas in the right corpus striatum were treated with direct intratumoral administration of AdmIL-12, AdLacZ, or normal saline. Survival was significantly prolonged in AdmIL-12-treated animals and immunohistochemistry demonstrated robust CD4+ and CD8+ T-cell infiltration in these mice compared to the two control groups. Glioma-infiltrating T lymphocytes from mice that received AdmIL-12 also demonstrated relatively increased, albeit statistically nonsignificant tumor killing. Based on IL-12's known ability to enhance Th1-type cytotoxic antitumor immune responses, we postulate our findings to be a result of localized induction of tumor immunity.

Neural stem cells as delivery vehicles.

The discovery of neural stem cells (NSCs) has changed our long-held view that the adult mammalian central nervous system (CNS) is postmitotic and lacks the capability for self-repair. The role of NSCs in physiological and pathological processes in the brain is slowly emerging. We are now able to isolate, expand, genetically engineer and transplant NSCs. An important characteristic of NSCs, not fully understood so far, is their migratory ability and their tropism to brain pathology. The migratory ability of NSCs and their capacity to differentiate into all neural phenotypes gives us a potentially powerful tool for the treatment of both diffuse and localised neurologic disorders. The delivery of gene products by NSCs to specific sites in the CNS can maximise the efficiency of delivery and minimise the unwanted exposure of surrounding intact tissue. Here, the recent preclinical advances in the use of NSCs for the delivery of therapeutic products are reviewed, in particular the employment of their migratory potential and the homing ability to pathology in the nervous system.

Recent progress in immunotherapy for malignant glioma: treatment strategies and results from clinical trials.

BACKGROUND: Despite advances in surgical and adjuvant radiation therapy and chemotherapy strategies, malignant gliomas continue to be associated with poor prognoses. METHODS: We review immune-mediated treatment approaches for malignant glioma and the relevance of recent clinical trials and their outcomes. We specifically address the increasing evidence implicating the role of cytotoxic T cells in ensuring adequate immune-mediated clearance of neoplastic cells and the need for the optimization of therapies that can elicit and support such antitumor T-cell activity. RESULTS: The poor outcome of this disease has spurred the search for novel experimental therapies that can address and overcome the root biological phenomena associated with the lethality of this disease. The use of immunotherapy to bolster the otherwise impaired antitumor immune responses in glioma patients has received increasing attention. CONCLUSIONS: An effective treatment paradigm for malignant gliomas may eventually require a multifaceted approach combining two or more different immunotherapeutic strategies. Such scenarios may involve the use of local cytokine gene therapy to enhance glioma-cell immunogenicity in conjunction with dendritic cell-based active vaccination to stimulate systemic tumoricidal T-cell immunity. Given the heterogeneity of this disease process and the potential risk of immunoediting out a selected, treatment-refractory tumor cell population, the concurrent use of multiple modalities that target disparate tumor characteristics may be of greatest therapeutic relevance.

A herpes simplex virus type 1 mutant with gamma 34.5 and LAT deletions effectively oncolyses human U87 glioblastomas in nude mice.

OBJECTIVE: We previously constructed a novel recombinant herpes simplex virus with deletions in the gamma 34.5 and LAT genes. LAT was replaced by the gene for green fluorescent protein, to allow monitoring of viral transduction in vitro and in vivo. We previously confirmed that this virus, designated DM33, retains its oncolytic properties in vitro and is inhibited with respect to spontaneous reactivation. The objective of this study was to demonstrate the therapeutic efficiency of this virus in the treatment of human gliomas in nude mice. METHODS: Thirty BALB/c nude mice underwent stereotactic implantation of U-87 MG gliomas in the right corpus striatum. Subsequently, mice received intratumoral inoculations of either DM33 (n = 20) or virus-free medium (n = 10). Ten mice given injections of DM33 were also treated intraperitoneally with ganciclovir. RESULTS: Intratumoral administration of DM33 to nude mice bearing intracranial U-87 MG human gliomas prolonged survival times, compared with saline-treated control animals (P < 0.05). Histological analyses of treated tumors demonstrated decreased tumor size and tumor cell lysis. Control tumors averaged 7.05 +/- 0.83 mm(2) (mean +/- standard error), whereas the average for the DM33 group was 4.61 +/- 1.57 mm(2) and that for the DM33 plus ganciclovir group was 2.49 +/- 1.32 mm(2). The difference in tumor sizes between the control group and the DM33 plus ganciclovir group was statistically significant (P = 0.044). Viral infection was limited to the tumors, and replication was not observed in normal neurons or glia. CONCLUSION: The efficacy of this virus in the treatment of experimental gliomas, its safety (as confirmed by its inability to reactivate), and its attenuated neurovirulence make DM33 a promising oncolytic agent for glioma therapy.

Development of an intracranial ependymoma at the site of a pre-existing cavernous malformation.

BACKGROUND: The ability of vascular anomalies to induce neoplastic transformation in normal brain parenchyma has been suggested but not demonstrated. We present a novel case in which a patient with a pre-existing cavernous malformation developed an adjacent ependymoma. CASE DESCRIPTION: A 72-year-old man developed an anaplastic ependymoma at the site of a pre-existing cavernous malformation. This is the first documented instance of an ependymoma developing at the site of an existing cavernous malformation. The colocalization of both lesions and the low incidence of supratentorial ependymomas in this age group makes it unlikely that their coexistence represents a random event. Immunohistochemistry demonstrated vascular endothelial growth factor (VEGF) production by the cavernous malformation and robust VEGF receptor expression by the ependymoma. CONCLUSIONS: Based on these findings, we suggest that production of VEGF by vascular malformations may play a role in the neoplastic transformation of adjacent tissue.

Surgical management of large scalp infantile hemangiomas.

BACKGROUND: Infantile Hemangiomas (IH) are the most common benign tumor of infancy, occurring in over 10% of newborns. While most IHs involute and never require intervention, some scalp IHs may cause severe cosmetic deformity and threaten tissue integrity that requires surgical excision. CASE DESCRIPTION: We present our experience with two infants who presented with large scalp IH. After vascular imaging, the patients underwent surgical resection of the IH and primary wound closure with excellent cosmetic outcome. We detail the surgical management of these cases and review the relevant literature. CONCLUSION: In some cases the IHs leave behind fibro-fatty residuum causing contour deformity. Surgery is often required for very large lesions causing extensive anatomical and/or functional disruption. The goal of surgical intervention is to restore normal anatomic contour and shape while minimizing the size of the permanent scar.

Resolution of trigeminal neuralgia by coil embolization of a persistent primitive trigeminal artery aneurysm.

The persistent primitive trigeminal artery (PTA) is a rare anastomosis between the carotid artery and basilar artery. While most PTAs are asymptomatic, lateral variants can occasionally compress the trigeminal nerve and precipitate trigeminal neuralgia. Aneurysms of the PTA are exceptionally rare in the literature and have not previously been associated with trigeminal neuralgia. We present the first case of an aneurysm of the PTA causing trigeminal neuralgia. The patient underwent coil embolization of the aneurysm which relieved her symptoms. We propose embolization as a viable therapeutic option for the resolution of trigeminal neuralgia when the condition is secondary to irritation by the high velocity pulsatile flow of an aneurysm.