Intercellular adhesion molecule-1 and blood-spinal cord barrier disruption in central nervous system radiation injury

Advances and prospects of tumor immunotherapy mediated by immune cell-derived biomimetic metal-organic frameworks

The clinical translational success of nanomedicine and immunotherapy has already proved the immense potential in the field of nanotechnology and immunization. However, the development of nanomedicine is confronted with challenges such as potential toxicity and unclear nano-bio interactions. The efficacy of immunotherapy is limited to only a few groups. Combining immunotherapy with nanomedicine for multi-modal treatment effectively compensates for the limitations of the above single therapy. Immune cell membrane camouflaged metal-organic frameworks (ICM-MOFs) have emerged as a simple yet promising multimodal treatment strategy that possess multifunctional nanoscale properties and exhibit immune cell-like behaviors of stealth, targeting and immunomodulation. Here, we comprehensively discuss the latest advancements in ICM-MOFs, with a focus on the challenges of mono-immunotherapy, the superiority of biomimetic coating for MOF functionalization, preparation methods, related action mechanisms and biomedical applications. Finally, we address the challenges and prospects for clinical translation.

The consequence of endothelial remodelling on the blood spinal cord barrier and nociception

Nociception is a fundamental acute protective mechanism that prevents harm to an organism. Understanding the integral processes that control nociceptive processing are fundamental to our appreciation of which cellular and molecular features underlie this process. There is an extensive understanding of how sensory neurons interpret differing sensory modalities and intensities. However, it is widely appreciated that the sensory neurons do not act alone. These work in harmony with inflammatory and vascular systems to modulate pain perception. The spinal cord has an extensive interaction with the capillary network in the form of a blood spinal cord barrier to ensure homeostatic control of the spinal cord neuron milieu. However, there is an extensive appreciation that disturbances in the blood spinal cord barrier contribute to the onset of chronic pain. Enhanced vascular permeability and impaired blood perfusion have both been highlighted as contributors to chronic pain manifestation. Here, we discuss the evidence that demonstrates alterations in the blood spinal cord barrier influences nociceptive processing and perception of pain.

Blood-Spinal Cord Barrier: Its Role in Spinal Disorders and Emerging Therapeutic Strategies

The blood-spinal cord barrier (BSCB) has been long thought of as a functional equivalent to the blood-brain barrier (BBB), restricting blood flow into the spinal cord. The spinal cord is supported by various disc tissues that provide agility and has different local immune responses compared to the brain. Though physiologically, structural components of the BSCB and BBB share many similarities, the clinical landscape significantly differs. Thus, it is crucial to understand the composition of BSCB and also to establish the cause-effect relationship with aberrations and spinal cord dysfunctions. Here, we provide a descriptive analysis of the anatomy, current techniques to assess the impairment of BSCB, associated risk factors and impact of spinal disorders such as spinal cord injury (SCI), amyotrophic lateral sclerosis (ALS), peripheral nerve injury (PNI), ischemia reperfusion injury (IRI), degenerative cervical myelopathy (DCM), multiple sclerosis (MS), spinal cavernous malformations (SCM) and cancer on BSCB dysfunction. Along with diagnostic and mechanistic analyses, we also provide an up-to-date account of available therapeutic options for BSCB repair. We emphasize the need to address BSCB as an individual entity and direct future research towards it.

Smart biomaterials to enhance the efficiency of immunotherapy in glioblastoma: State of the art and future perspectives

Glioblastoma multiform (GBM) is considered as the most lethal tumor among CNS malignancies. Although immunotherapy has achieved remarkable advances in cancer treatment, it has not shown satisfactory results in GBM patients. Biomaterial science, along with nanobiotechnology, is able to optimize the efficiency of immunotherapy in these patients. They can be employed to provide the specific activation of immune cells in tumor tissue and combinational therapy as well as preventing systemic adverse effects resulting from hyperactivation of immune responses and off-targeting effect. Advance biomaterials in this field are classified into targeting nanocarriers and localized delivery systems. This review will offer an overview of immunotherapy strategies for glioblastoma and advance delivery systems for immunotherapeutics that may have a high potential in glioblastoma treatment.

Immunocyte Membrane-Coated Nanoparticles for Cancer Immunotherapy

Despite the advances in surface bioconjugation of synthetic nanoparticles for targeted drug delivery, simple biological functionalization is still insufficient to replicate complex intercellular interactions naturally. Therefore, these foreign nanoparticles are inevitably exposed to the immune system, which results in phagocytosis by the reticuloendothelial system and thus, loss of their biological significance. Immunocyte membranes play a key role in intercellular interactions, and can protect foreign nanomaterials as a natural barrier. Therefore, biomimetic nanotechnology based on cell membranes has developed rapidly in recent years. This paper summarizes the development of immunocyte membrane-coated nanoparticles in the immunotherapy of tumors. We will introduce several immunocyte membrane-coated nanocarriers and review the challenges to their large-scale preparation and application.

Clinical Perspectives in Brain Metastasis

Brain metastases (BMs) are responsible for decline in neurological function, reduction in overall quality of life, and mortality from recurrent or untreatable lesions. Advances in diagnostics and imaging have led to increased detection of central nervous system (CNS) metastases in patients with progressive cancers. Improved control of extracranial systemic disease, and the limited ability of current therapeutics to cross the blood-brain barrier (BBB) also contribute to the increase in incidence of brain metastases, as tumor cells seek refuge in the brain. Surgery, chemotherapy, and/or radiation (whole-brain radiation therapy and stereotactic radiation surgery [WBRT/SRS]) are a clinically established treatment paradigm for patients with brain metastases. With the advent of genetic and molecular characterization of tumors and their immune microenvironment, clinical trials seek to include targeted drugs into the therapeutic regimen for eligible patients. Several challenges, like treatment of multiple CNS lesions, superior uptake of chemotherapy into the brain, and trials with multidisciplinary approaches, are now being clinically addressed.

Brain metastases from germ cell tumor: time to reconsider radiotherapy?

The presence of brain metastases (BMs) from germ cell tumor (GCT) remains a rare situation. BMs predominantly occur among patients with testis primary tumor site, and are almost exclusively associated with non-seminomatous (NS) histologies. Two situations must be distinguished, which differ in terms of clinical presentation, overall prognostic and management. At diagnosis, BMs are almost systematically associated with extra-cerebral metastases and the cornerstone of treatment is chemotherapy, while the role of local treatment remains controversial. In the metachronous setting, BMs more frequently constitute an isolated site of relapse, the outcome is poorer, and the role of local treatment is more consensual. However, all these data widely come from old reports, with outdated radiation techniques. The recent advances in radiation oncology, especially the rising use of stereotactic radiotherapy, could lead to the reconsideration of ancient dogmas regarding the "radiosensitivity" of (NS)GCT and the role of radiotherapy among patients with BMs.

Mitigating effect of biotin against irradiation-induced cerebral cortical and hippocampal damage in the rat brain tissue

Radiation-induced brain injury is common and mainly occurs in patients receiving radiotherapy for malignant head and neck tumors. The brain is oversensitive to oxidant injury induced by radiation. Biotin is a member of the vitamin B complex family and its deficiency has been associated with neurogenesis impairment in animals and humans. The present study was undertaken to investigate the mitigating effect of biotin on the cerebral cortical and hippocampal damage induced by radiation exposure. Animals were exposed to radiation in the presence or absence of biotin and sacrificed on day 10. The results demonstrated that the administration of biotin 2 mg to irradiated rats had no significant effect on the radiation-induced damage of the cerebral cortex and the hippocampus, while the administration of biotin 6 mg has significantly attenuated oxidative stress in the hippocampus, manifested by a reduction of 4-hydroxynonenal (4HNE), total nitrate/nitrite (NOx), and xanthine oxidase (XO) levels associated with an elevation of glutathione (GSH) content as well as superoxide dismutase (SOD) and catalase (CAT) activities. In addition, biotin decreased the pro-inflammatory cytokines (interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrotic factor alpha (TNF-α)), caspase-3, poly(ADP-ribose) polymerase 1 (PARP1) level, and PARP1 gene expression. Moreover, biotin 6 mg treatment diminished serum S100 protein (S100B) and neuron-specific enolase (NSE) levels. In conclusion, biotin treatment at high dose post-irradiation has efficiently neutralized the effect of free radicals in the hippocampal region of rats. Thus, it could be applicable as a radio-mitigator for reducing or delayed radiation-induced brain injury in patients post-radiotherapy.

Diagnosis and Management of Radiation Necrosis in Patients With Brain Metastases

The use of radiotherapy, either in the form of stereotactic radiosurgery (SRS) or whole-brain radiotherapy (WBRT), remains the cornerstone for the treatment of brain metastases (BM). As the survival of patients with BM is being prolonged, due to improved systemic therapy (i.e., for better extra-cranial control) and increased use of SRS (i.e., for improved intra-cranial control), patients are clinically manifesting late effects of radiotherapy. One of these late effects is radiation necrosis (RN). Unfortunately, symptomatic RN is notoriously hard to diagnose and manage. The features of RN overlap considerably with tumor recurrence, and misdiagnosing RN as tumor recurrence may lead to deleterious treatment which may cause detrimental effects to the patient. In this review, we will explore the pathophysiology of RN, risk factors for its development, and the strategies to evaluate and manage RN.

Mechanisms of inflammatory responses to radiation and normal tissues toxicity: clinical implications

PURPOSE

Cancer treatment is one of the most challenging diseases in the present era. Among a few modalities for cancer therapy, radiotherapy plays a pivotal role in more than half of all treatments alone or combined with other cancer treatment modalities. Management of normal tissue toxicity induced by radiation is one of the most important limiting factors for an appropriate radiation treatment course. The evaluation of mechanisms of normal tissue toxicity has shown that immune responses especially inflammatory responses play a key role in both early and late side effects of exposure to ionizing radiation (IR). DNA damage and cell death, as well as damage to some organelles such as mitochondria initiate several signaling pathways that result in the response of immune cells. Massive cell damage which is a common phenomenon following exposure to a high dose of IR cause secretion of a lot of inflammatory mediators including cytokines and chemokines. These mediators initiate different changes in normal tissues that may continue for a long time after irradiation. In this study, we reviewed the mechanisms of inflammatory responses to IR that are involved in normal tissue toxicity and considered as the most important limiting factors in radiotherapy. Also, we introduced some agents that have been proposed for management of these responses.

CONCLUSIONS

The early inflammation during the radiation treatment is often a limiting factor in radiotherapy. In addition to the limiting factors, chronic inflammatory responses may increase the risk of second primary cancers through continuous free radical production, attenuation of tumor suppressor genes, and activation of oncogenes. Moreover, these effects may influence non-irradiated tissues through a mechanism named bystander effect.

Targeting the blood-spinal cord barrier: A therapeutic approach to spinal cord protection against ischemia-reperfusion injury

One of the principal functions of physical barriers between the blood and central nervous system protects system (i.e., blood brain barrier and blood-spinal cord barrier) is the protection from toxic and pathogenic agents in the blood. Disruption of blood-spinal cord barrier (BSCB) plays a key role in spinal cord ischemia-reperfusion injury (SCIRI). Following SCIRI, the permeability of the BSCB increases. Maintaining the integrity of the BSCB alleviates the spinal cord injury after spinal cord ischemia. This review summarizes current knowledge of the structure and function of the BSCB and its changes following SCIRI, as well as the prevention and cure of SCIRI and the role of the BSCB.

Pathophysiology, diagnosis, and treatment of radiation necrosis in the brain

New radiation modalities have made it possible to prolong the survival of individuals with malignant brain tumors, but symptomatic radiation necrosis becomes a serious problem that can negatively affect a patient’s quality of life through severe and lifelong effects. Here we review the relevant literature and introduce our original concept of the pathophysiology of brain radiation necrosis following the treatment of brain, head, and neck tumors. Regarding the pathophysiology of radiation necrosis, we introduce two major hypotheses: glial cell damage or vascular damage. For the differential diagnosis of radiation necrosis and tumor recurrence, we focus on the role of positron emission tomography. Finally, in accord with our hypothesis regarding the pathophysiology, we describe the promising effects of the anti-vascular endothelial growth factor antibody bevacizumab on symptomatic radiation necrosis in the brain.

Multiple injections of human umbilical cord-derived mesenchymal stromal cells through the tail vein improve microcirculation and the microenvironment in a rat model of radiation myelopathy

Background

At present, no effective clinical treatment is available for the late effects of radiation myelopathy. The aim of the present study was to assess the therapeutic effects of human umbilical cord-derived mesenchymal stromal cells (UC-MSCs) in a rat model of radiation myelopathy.

Methods

An irradiated cervical spinal cord rat model was generated. UC-MSCs were injected through the tail vein at 90, 97, 104 and 111 days post-irradiation. Behavioral tests were performed using the forelimb paralysis scoring system, and histological damage was examined using Nissl staining. The microcirculation in the spinal cord was assessed using von Willebrand factor (vWF) immunohistochemical analysis and laser-Doppler flowmetry. The microenvironment in the spinal cord was determined by measuring the pro-inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the serum and the anti-inflammatory cytokines brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF) in the spinal cord.

Results

Multiple injections of UC-MSCs through the tail veil decreased the forelimb paralysis, decreased spinal cord histological damage, increased the number of neurons in the anterior horn of the spinal cord, increased the endothelial cell density and the microvessel density in the white matter and gray matter of the spinal cord, increased the relative magnitude of spinal cord blood flow, down-regulated pro-inflammatory cytokine expression in the serum, and increased anti-inflammatory cytokine expression in the spinal cord.

Conclusion

Multiple injections of UC-MSCs via the tail vein in a rat model of radiation myelopathy significantly improved the microcirculation and microenvironment through therapeutic paracrine effects.

Radiation-induced endothelial cell loss and reduction of the relative magnitude of the blood flow in the rat spinal cord

The main purpose of the present study was to examine the time-dependent alterations in the endothelial cell density that occur in the first 180 days after irradiation of the spinal cord and the functional role of these alterations in the spinal cord blood flow. An irradiated cervical spinal cord rat model (C2-T2 segment) was generated using a (60)Co irradiator to deliver 30 Gy. A significant loss of forelimb motor function was observed 180 days post-irradiation. The number of neurons in the anterior horn of the spinal cord began to decrease significantly 3 days post-irradiation compared with normal controls, reaching the lowest number at 90 days post-irradiation. A significant reduction in the endothelial cell density was observed from 14 days post-irradiation in the white matter and from 3 days post-irradiation in the gray matter. The lowest endothelial cell density was reached at 30 days post-irradiation in the white matter and at 60 days post-irradiation in the gray matter. A significant reduction in the microvessel density was observed from 3 days post-irradiation in both the white matter and the gray matter. The lowest microvessel density was reached at 90 days post-irradiation in both the white matter and the gray matter. A significant reduction in the relative magnitude of spinal cord blood flow was observed from 21 days post-irradiation. The lowest relative magnitude of spinal cord blood flow was reached at 90 days post-irradiation. We did not find any evidence of demyelination. The results revealed that a single 30-Gy irradiation dose resulted in impaired forelimb motor function, a decreased number of neurons, and reduced endothelial cell density, microvessel density and relative magnitude of spinal cord blood flow. However, a 30-Gy single-dose irradiation was not sufficient to induce demyelination in the rat spinal cord.

Cerebral radiation necrosis: a review of the pathobiology, diagnosis and management considerations

Radiation therapy forms one of the building blocks of the multi-disciplinary management of patients with brain tumors. Improved survival following radiation therapy may come with a cost, including the potential complication of radiation necrosis. Radiation necrosis impacts the quality of life in cancer survivors, and it is essential to detect and effectively treat this entity as early as possible. Significant progress in neuro-radiology and molecular pathology facilitate more straightforward diagnosis and characterization of cerebral radiation necrosis. Several therapeutic interventions, both medical and surgical, may halt the progression of radiation necrosis and diminish or abrogate its clinical manifestations, but there are still no definitive guidelines to follow explicitly that guide treatment of radiation necrosis. We discuss the pathobiology, clinical features, diagnosis, available treatment modalities, and outcomes in the management of patients with intracranial radiation necrosis that follows radiation used to treat brain tumors.

Magnetic resonance imaging of radiation-induced brain injury using targeted microparticles of iron oxide

BACKGROUND

Radiation-induced brain injury (RBI) is the most serious complication of primary and metastatic brain and neck malignant tumors following radiation therapy. However, at present, RBI is difficult to diagnose in the early period. Recently, studies have demonstrated that the early stage of RBI is characterized by an inflammatory reaction, and that intercellular adhesion molecule-1 (ICAM-1) is significantly up-regulated in the irradiated brain tissues.

PURPOSE

To provide an early diagnosis of RBI using molecular magnetic resonance imaging (MRI) with microparticles of iron oxide (MPIO) targeted to ICAM-1 in the vascular endothelium of brains.

MATERIAL AND METHODS

A monoclonal antibody against ICAM-1 was conjugated to MPIO to form the targeted MRI contrast agent ICAM-MPIO. The adhesion of ICAM-MPIO to endothelial cells was quantified by optical imaging and MRI. Sprague-Dawley rats were irradiated to establish an animal model of the early period of RBI. ICAM-MPIO and free-MPIO were injected via tail vein, respectively. T(2) signal intensity and T(2) values of the irradiated brains and normal brains were subsequently evaluated by MRI.

RESULTS

In vitro, the adhesion of ICAM-MPIO to the activated endothelial cells was 5 ± 0.5-fold greater than to the non-stimulated cells, which could be detected by optical imaging and MRI (R(2) = 1.0, P < 0.01). In vivo, ICAM-MPIO caused a marked negative MRI contrast effect in irradiated brains. As compared with brains without irradiation, the specific contrast effect increased more than seven-fold after administration of ICAM-MPIO (F = 751.495, P < 0.05).

CONCLUSION

MPIO coated with monoclonal antibody of ICAM-1 could be used for detecting the early period of RBI by optical imaging and MRI.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Radiation necrosis following treatment of high grade glioma--a review of the literature and current understanding

Radiation therapy is an integral part of the standard treatment paradigm for malignant gliomas, with proven efficacy in randomized control trials. Radiation treatment is not without risk however, and radiation injury occurs in a certain proportion of patients. Difficulties in differentiating recurrence from radiation injury complicate the treatment course and can compromise care. These complexities are compounded by the recent distinction of two types of radiation injury: pseudoprogression and radiation necrosis, which are likely the result of radiation injury to the tumor and normal tissue, respectively. A thorough understanding of radiation-induced injury offers insights to guide further therapies. We detail the current knowledge of the mechanisms of radiation injury, along with potential targets for therapeutic intervention. Various diagnostic modalities are also described, in addition to the multiple options for treatment within the context of their pathophysiology and clinical efficacy. Radiation therapy is an integral part of the multidisciplinary management of gliomas, and the optimal diagnosis and management of radiation injury is paramount to improving patient outcomes.

Diet-induced effects on neuronal and glial elements in the middle-aged rat hippocampus

Consumption of a high-fat and/or high-cholesterol diet can have detrimental effects on the brain. In the present study, dietary treatment with saturated fats, trans fats, or cholesterol to middle-aged Fischer 344 rats resulted in alterations to serum triglyceride and cholesterol levels, organ weights, and hippocampal morphology. Previously, we demonstrated that a 10% hydrogenated coconut oil and 2% cholesterol diet resulted in worse performance on the 12-day water radial arm maze, increased cholesterol and triglyceride levels, and decreased dendritic microtubule associated protein 2 (MAP2) staining in the hippocampus. The diets administered herein were used to examine components from the previous diet and further examine their effects on hippocampal morphology. Specifically, neuronal morphology, dendritic integrity, fatty acid metabolism, microgliosis, and blood vessel structure in the hippocampus and/or adjacent structures were explored. Our results indicate alterations to peripheral and neural systems following each of the diets.

The blood-spinal cord barrier: morphology and clinical implications

The blood-spinal cord barrier (BSCB) is the functional equivalent of the blood-brain barrier (BBB) in the sense of providing a specialized microenvironment for the cellular constituents of the spinal cord. Even if intuitively the BSCB could be considered as the morphological extension of the BBB into the spinal cord, evidence suggests that this is not so. The BSCB shares the same principal building blocks with the BBB; nevertheless, it seems that morphological and functional differences may exist between them. Dysfunction of the BSCB plays a fundamental role in the etiology or progression of several pathological conditions of the spinal cord, such as spinal cord injury, amyotrophic lateral sclerosis, and radiation-induced myelopathy. This review summarizes current knowledge of the morphology of the BSCB, the methodology of studying the BSCB, and the potential role of BSCB dysfunction in selected disorders of the spinal cord, and finally summarizes therapeutic approaches to the BSCB.

Role of intercellular adhesion molecule-1 in radiation-induced brain injury

PURPOSE

To determine the role of intercellular adhesion molecule-1 (ICAM-1) in the pathogenesis of brain injury after irradiation (IR).

METHODS AND MATERIALS

We assessed the expression of ICAM-1 in mouse brain after cranial IR and determined the histopathologic and behavioral changes in mice that were either wildtype (+/+) or knockout (-/-) of the ICAM-1 gene after IR.

RESULTS

There was an early dose-dependent increase in ICAM-1 mRNA and protein expression after IR. Increased ICAM-1 immunoreactivity was observed in endothelia and glia of ICAM-1+/+ mice up to 8 months after IR. ICAM-1-/- mice showed no expression. ICAM-1+/+ and ICAM-1-/- mice showed similar vascular abnormalities at 2 months after 10-17 Gy, and there was evidence for demyelination and inhibition of hippocampal neurogenesis at 8 months after 10 Gy. After 10 Gy, irradiated ICAM-1+/+ and ICAM-1-/- mice showed similar behavioral changes at 2-6 months in open field, light-dark chamber, and T-maze compared with age-matched genotype controls.

CONCLUSION

There is early and late upregulation of ICAM-1 in the vasculature and glia of mouse brain after IR. ICAM-1, however, does not have a causative role in the histopathologic injury and behavioral dysfunction after moderate single doses of cranial IR.

CNS complications of radiotherapy and chemotherapy

Treatment-induced CNS toxicity remains a major cause of morbidity in patients with cancer. Advances in the design of safe radiation procedures have been counterbalanced by widespread use of combined radiotherapy and chemotherapy, development of radiosurgery, and the increasing number of long-term survivors. Although classic radionecrosis and chemonecrosis have become less common, subtle changes such as progressive cognitive dysfunction are increasingly reported after radiotherapy (radiation-induced leukoencephalopathy) or chemotherapy (given alone or in combination). We review the most important and controversial complications of radiotherapy, chemotherapy, and combined treatments in the CNS, and discuss new diagnostic tools, practical management, prevention, and pathophysiological data that will affect future management of patients with cancer.

Clinical biomarkers of angiogenesis inhibition

INTRODUCTION

An expanding understanding of the importance of angiogenesis in oncology and the development of numerous angiogenesis inhibitors are driving the search for biomarkers of angiogenesis. We review currently available candidate biomarkers and surrogate markers of anti-angiogenic agent effect.

DISCUSSION

A number of invasive, minimally invasive, and non-invasive tools are described with their potential benefits and limitations. Diverse markers can evaluate tumor tissue or biological fluids, or specialized imaging modalities.

CONCLUSIONS

The inclusion of these markers into clinical trials may provide insight into appropriate dosing for desired biological effects, appropriate timing of additional therapy, prediction of individual response to an agent, insight into the interaction of chemotherapy and radiation following exposure to these agents, and perhaps most importantly, a better understanding of the complex nature of angiogenesis in human tumors. While many markers have potential for clinical use, it is not yet clear which marker or combination of markers will prove most useful.

Gamma-ray irradiation stimulates the expression of caveolin-1 and GFAP in rat spinal cord: a study of immunoblot and immunohistochemistry

We studied the expression of caveolin-1 in the spinal cords of rats using 60Co gamma-ray irradiation (single dose of 8 Gray (Gy)) in order to determine the possible involvement of caveolin-1 in the tissues of the central nervous system after irradiation. Spinal cords sampled at days 1, 4, and 9 post-irradiation (PI) (n = 5 per each time point) were analyzed by Western blot and immunohistochemistry. Western blot analysis showed that the expression of caveolin-1 was significantly increased at day 1 PI (p < 0.05), and returned to the level of normal control rats on days 4 and 9 PI. Immunohistochemistry showed that caveolin-1 immunoreactivity was enhanced in some glial cells, vascular endothelial cells, and neurons in the spinal cords. The increased expression of glial fibrillary acidic protein (GFAP), a marker for an astroglial reaction, was consistent with that of caveolin-1. In addition, caveolin-1 was co-localized in hypertrophied GFAP-positive astrocytes. Taking all these facts into consideration, we postulate that irradiation induces the increased expression of caveolin-1 in cells of the central nervous system, and that its increased expression in astrocytes may contribute to hypertrophy of astrocytes in the spinal cord after irradiation. The precise role of caveolin-1 in the spinal cords should be studied further.

Distribution of ICAM-1 immunoreactivity during aging in the human orbitofrontal cortex

Neurological and psychiatric alterations during aging are associated with increased cerebrovascular disturbances and inflammatory markers such as Intercellular Adhesion Molecule-1 (ICAM-1). We investigated whether the distribution of ICAM-1 immunoreactivity (ICAM-1-I) in histological sections from the left orbitofrontal cortex (ORB) was altered during normal aging. Postmortem tissue from the ORB of nine younger (27-54 years old) and 10 older (60-86) human subjects was collected. Cryostat sections were immunostained only with antibodies to ICAM-1 or together with an antibody to glial fibrillary acidic protein (GFAP). The total area fraction of ICAM-1-I, and the fraction of vascular and extravascular ICAM-1-I were quantified in the gray matter. Furthermore, we examined the association of extravascular ICAM-1-I to GFAP immunoreactive (GFAP-IR) astrocytes. In all subjects, brain blood vessels were similarly ICAM-1 immunoreactive, and in some subjects there was a variable number of extravascular patches of ICAM-1-I. The area fraction of ICAM-1-I was 120% higher (p<.0001) in the old subjects than in the young subjects. This increase localized mostly to the extravascular ICAM-1-I in register with GFAP-IR astrocytes. A much smaller, also age-dependent increase occurred in vascular ICAM-1-I. Our results indicate a dramatic increase in extravascular ICAM-1-I associated to GFAP-IR astrocytes in the ORB in normal aging. This increase may contribute to an enhanced risk for brain inflammatory processes during aging, although a role of extravascular ICAM-1 as a barrier to further inflammation cannot be ruled out.

Isolation and culture of microvascular endothelial cells from murine spinal cord

The isolation and culture of spinal cord microvascular endothelial cells (SCMEC), which form the blood-spinal cord barrier (BSCB), is described. Though morphologically similar to brain microvascular endothelial cells (BMEC) that form the blood-brain barrier (BBB), SCMEC express reduced amounts of several prominent BBB proteins, including tight junction-associated proteins ZO-1 and occludin, adherens junction-associated proteins beta-catenin and VE-cadherin, and the efflux transporter P-glycoprotein. These distinguishing features may reflect more widespread differences between the BBB and BSCB that impact physiological and pathophysiological processes.

Combining radiotherapy and angiogenesis inhibitors: clinical trial design

Radiotherapy (RT) plays a vital role in the multimodality treatment of cancer. Recent advances in RT have primarily involved improvements in dose delivery. Future improvements in tumor control and disease outcomes will likely involve the combination of RT with targeted therapies. Preclinical evaluations of angiogenesis inhibitors in combination with RT have yielded promising results with increased tumor "cure." It remains to be seen whether these improvements in tumor control in the laboratory will translate into improved outcomes in the clinic. Multiple differences between these agents and cytotoxic chemotherapy must be taken into account when designing clinical trials evaluating their effectiveness in combination with RT. We discuss important considerations for designing clinical trials of angiogenesis inhibitors with RT.

Cognitive sequelae of brain tumor treatment

PURPOSE OF REVIEW

The neurocognitive sequelae of anticancer treatment have received increasing attention especially among individuals with low-grade gliomas, primary central nervous system lymphoma and those undergoing prophylactic cranial irradiation for systemic malignancies. These groups are especially vulnerable because they often experience extended survival during which neurocognitive complications of therapy may cause more impairment than the tumor itself. The purpose of this review is to highlight recent clinical reports of neurocognitive sequelae among patients without significant central nervous system tumor burden and to describe the experimental studies which may explain the pathogenesis of the disorder.

RECENT FINDINGS

The neurocognitive deficits among survivors of primary central nervous system lymphoma without residual tumor and pituitary tumors were reported recently. Both provide an opportunity to distinguish the effects of treatment from the effects of tumor. Moreover, animal studies demonstrate the negative consequences of radiation on hippocampal neurogenesis, learning and memory. The mechanism of impaired neurogenesis may be due to inflammation, which can be aborted with restoration of neurogenesis through the administration of non-steroidal anti-inflammatory agents.

SUMMARY

If inhibition of neurogenesis is the basis of neurocognitive sequelae from irradiation and non-steroidal anti-inflammatory agents can restore neurogenesis then a clinical trial may be worthwhile to confirm this benefit in humans.

Radiation-induced up-regulation of adhesion molecules in brain microvasculature and their modulation by dexamethasone

Little is known about the time course and magnitude of the up-regulation of endothelial cell adhesion molecules (ECAMs) in irradiated brain vasculature and the mechanisms by which dexamethasone modulates this up-regulation. We used antibody-conjugated microspheres and a rat closed cranial window model to determine the time course of functional up-regulation of radiation (20 Gy)-induced ICAM1, E-selectin and P-selectin in the pial vasculature of the rat brain and to determine the relationship between suppression of inflammation by dexamethasone and the expression of these ECAMs. The results indicate that ICAM1, E-selectin and P-selectin were up-regulated to a functional level in the microvasculature with distinct time-course patterns. The number of adherent anti-E-selectin and anti-P-selectin microspheres was 5- 12 times greater than that of IgG microspheres 3-6 h postirradiation, and their expression returned to normal at 48 h. The number of adherent anti-ICAM1 microspheres was five and nine times greater than that of IgG at 24 and 48 h, respectively, and returned to baseline by 7 days. Dexamethasone significantly reduced the number of adhering leukocytes and the number of adhering anti-ICAM1, anti-E-selectin and anti-P-selectin microspheres to background levels. Our findings partially identify a key sequence in radiation-induced inflammatory response and provide a potential means to limit radiation-induced inflammatory responses and their potential side effects in the brain.

Molecular targets in radiation-induced blood-brain barrier disruption

Disruption of the blood-brain barrier (BBB) is a key feature of radiation injury to the central nervous system. Studies suggest that endothelial cell apoptosis, gene expression changes, and alteration of the microenvironment are important in initiation and progression of injury. Although substantial effort has been directed at understanding the impact of radiation on endothelial cells and oligodendrocytes, growing evidence suggests that other cell types, including astrocytes, are important in responses that include induced gene expression and microenvironmental changes. Endothelial apoptosis is important in early BBB disruption. Hypoxia and oxidative stress in the later period that precedes tissue damage might lead to astrocytic responses that impact cell survival and cell interactions. Cell death, gene expression changes, and a toxic microenvironment can be viewed as interacting elements in a model of radiation-induced disruption of the BBB. These processes implicate particular genes and proteins as targets in potential strategies for neuroprotection.

The sequelae of cranial irradiation on human cognition

Cranial irradiation (CI) confers remediation of many CNS anomalies. CI, however, carries risks to cognitive performance. A wealth of data describes such deficits specifically in humans. Risk factors that promote increased susceptibility to cognitive decline have also been identified. This paper discusses and grades these risk factors, including age, gender, and the inclusion of chemotherapy, that increase the likelihood of pathologic cognitive development in the human population.