Glioma stem cell research for the development of immunotherapy

Using nanotechnology to progress the utilization of marine natural products in combating multidrug resistance in cancer: A prospective strategy

Achieving targeted, customized, and combination therapies with clarity of the involved molecular pathways is crucial in the treatment as well as overcoming multidrug resistance (MDR) in cancer. Nanotechnology has emerged as an innovative and promising approach to address the problem of drug resistance. Developing nano-formulation-based therapies using therapeutic agents poses a synergistic effect to overcome MDR in cancer. In this review, we aimed to highlight the important pathways involved in the progression of MDR in cancer mediated through nanotechnology-based approaches that have been employed to circumvent them in recent years. Here, we also discussed the potential use of marine metabolites to treat MDR in cancer, utilizing active drug-targeting nanomedicine-based techniques to enhance selective drug accumulation in cancer cells. The discussion also provides future insights for developing complex targeted, multistage responsive nanomedical drug delivery systems for effective cancer treatments. We propose more combinational studies and their validation for the possible marine-based nanoformulations for future development.

The Role of Cellular Immunity and Adaptive Immunity in Pathophysiology of Brain and Spinal Cord Tumors

Major advances have been made in our understanding of CNS tumors, especially glioma, however, the survival of patients with malignant glioma remains poor. While radiation and chemotherapy have increased overall survival, glioblastoma multiforme (GBM) still has one of the worst 5-year survival rates of all human cancers. Here, in this chapter, the authors review the abrogation of the immune system in the tumor setting, revealing many plausible targets for therapy and the current immunotherapy treatment strategies employed. Notably, glioma has also been characterized as a subset of primary spinal cord tumor and current treatment recommendations are outlined here.

Local Delivery and Glioblastoma: Why Not Combining Sustained Release and Targeting?

Glioblastoma is one of the most aggressive brain tumors and is associated with a very low overall median survival despite the current treatment. The standard of care used in clinic is the Stupp's protocol which consists of a maximal resection of the tumor when possible, followed by radio and chemotherapy using temozolomide. However, in most cases, glioblastoma cells infiltrate healthy tissues and lead to fatal recurrences. There are a lot of hurdles to overcome in the development of new therapeutic strategies such as tumor heterogeneity, cell infiltration, alkylating agent resistance, physiological barriers, etc., and few treatments are on the market today. One of them is particularly appealing because it is a local therapy, which does not bring additional invasiveness since tumor resection is included in the gold standard treatment. They are implants: the Gliadel^® wafers, which are deposited post-surgery. Nevertheless, in addition to presenting important undesirable effects, it does not bring any major benefit in the therapy despite the strategy being particularly attractive. The purpose of this review is to provide an overview of recent advances in the development of innovative therapeutic strategies for glioblastoma using an implant-type approach. The combination of this local strategy with effective targeting of the tumor microenvironment as a whole, also developed in this review, may be of interest to alleviate some of the obstacles encountered in the treatment of glioblastoma.

Stem Cell Differentiation Stage Factors and their Role in Triggering Symmetry Breaking Processes during Cancer Development: A Quantum Field Theory Model for Reprogramming Cancer Cells to Healthy Phenotypes

A long history of research has pursued the use of embryonic factors isolated during cell differentiation processes for the express purpose of transforming cancer cells back to healthy phenotypes. Recent results have clarified that the substances present at different stages of cell differentiation-which we call stem cell differentiation stage factors (SCDSFs)-are proteins with low molecular weight and nucleic acids that regulate genomic expression. The present review summarizes how these substances, taken at different stages of cellular maturation, are able to retard proliferation of many human tumor cell lines and thereby reprogram cancer cells to healthy phenotypes. The model presented here is a quantum field theory (QFT) model in which SCDSFs are able to trigger symmetry breaking processes during cancer development. These symmetry breaking processes, which lie at the root of many phenomena in elementary particle physics and condensed matter physics, govern the phase transitions of totipotent cells to higher degrees of diversity and order, resulting in cell differentiation. In cancers, which share many genomic and metabolic similarities with embryonic stem cells, stimulated redifferentiation often signifies the phenotypic reversion back to health and nonproliferation. In addition to acting on key components of the cellular cycle, SCDSFs are able to reprogram cancer cells by delicately influencing the cancer microenvironment, modulating the electrochemistry and thus the collective electrodynamic behaviors between dipole networks in biomacromolecules and the interstitial water field. Coherent effects in biological water, which are derived from a dissipative QFT framework, may offer new diagnostic and therapeutic targets at a systemic level, before tumor instantiation occurs in specific tissues or organs. Thus, by including the environment as an essential component of our model, we may push the prevailing paradigm of mutation-driven oncogenesis toward a closer description of reality.

Characterization of Ablation Thresholds for 3D-Cultured Patient-Derived Glioma Stem Cells in Response to High-Frequency Irreversible Electroporation

High-frequency irreversible electroporation (H-FIRE) is a technique that uses pulsed electric fields that have been shown to ablate malignant cells. In order to evaluate the clinical potential of H-FIRE to treat glioblastoma (GBM), a primary brain tumor, we have studied the effects of high-frequency waveforms on therapy-resistant glioma stem-like cell (GSC) populations. We demonstrate that patient-derived GSCs are more susceptible to H-FIRE damage than primary normal astrocytes. This selectivity presents an opportunity for a degree of malignant cell targeting as bulk tumor cells and tumor stem cells are seen to exhibit similar lethal electric field thresholds, significantly lower than that of healthy astrocytes. However, neural stem cell (NSC) populations also exhibit a similar sensitivity to these pulses. This observation may suggest that different considerations be taken when applying these therapies in younger versus older patients, where the importance of preserving NSC populations may impose different restrictions on use. We also demonstrate variability in threshold among the three patient-derived GSC lines studied, suggesting the need for personalized cell-specific characterization in the development of potential clinical procedures. Future work may provide further useful insights regarding this patient-dependent variability observed that could inform targeted and personalized treatment.

Periarteriolar Glioblastoma Stem Cell Niches Express Bone Marrow Hematopoietic Stem Cell Niche Proteins

In glioblastoma, a fraction of malignant cells consists of therapy-resistant glioblastoma stem cells (GSCs) residing in protective niches that recapitulate hematopoietic stem cell (HSC) niches in bone marrow. We have previously shown that HSC niche proteins stromal cell-derived factor-1α (SDF-1α), C-X-C chemokine receptor type 4 (CXCR4), osteopontin (OPN), and cathepsin K (CatK) are expressed in hypoxic GSC niches around arterioles in five human glioblastoma samples. In HSC niches, HSCs are retained by binding of SDF-1α and OPN to their receptors CXCR4 and CD44, respectively. Protease CatK cleaves SDF-1α to release HSCs out of niches. The aim of the present study was to reproduce the immunohistochemical localization of these GSC markers in 16 human glioblastoma samples with the addition of three novel markers. Furthermore, we assessed the type of blood vessels associated with GSC niches. In total, we found seven GSC niches containing CD133-positive and nestin-positive GSCs as a single-cell layer exclusively around the tunica adventitia of 2% of the CD31-positive and SMA-positive arterioles and not around capillaries and venules. Niches expressed SDF-1α, CXCR4, CatK, OPN, CD44, hypoxia-inducible factor-1α, and vascular endothelial growth factor. In conclusion, we show that GSC niches are present around arterioles and express bone marrow HSC niche proteins.

MicroRNA‑141 inhibits the self‑renewal of glioblastoma stem cells via Jagged1

Glioblastoma multiforme is one of the most lethal types of brain cancer. With limited success from conventional therapies, the cancer stem cell theory was developed, and investigation into microRNAs (miRs) has facilitated understanding of this theory. The present study demonstrated that miR-141 is suppressed in sorted cluster of differentiation (CD) 133(+) glioblastoma stem cells (GSCs) compared with CD133(−) non-glioblastoma stem cells (NSCs) from patient samples. In addition, miR-141 overexpression inhibited the sphere formation ability of GSCs in vitro and in vivo. Furthermore, Jagged1 may reverse the effect of miR-141; miR-141 was revealed to target the 3′-untranslated region of Jagged1, thereby inhibiting the stemness of GSCs. Thus, miR-141 may serve as a potent antioncomir targeting cancer stem cells, and may facilitate the development of therapeutic targets to prolong the overall survival of patients with glioblastoma.

Epigenetic Regulation of CD133 in Gastrointestinal Stromal Tumors

OBJECTIVES

This study ascertained the regulation of the stem cell marker CD133 and its potential applicability for prognostication of gastrointestinal stromal tumors (GISTs).

METHODS

A total of 95 resected GISTs were included in the study. CD133 protein expression was assessed immunohistochemically on tissue microarrays. Methylation percentage was quantified by pyrosequencing. Gene expression in cell lines GIST48b and GIST882 upon treatment with DNA demethylation agent 5-aza-2'-deoxycytidine was analyzed by quantitative polymerase chain reaction.

RESULTS

The expression of hypermethylated CD133 could be reactivated in the GIST cell line upon hypomethylation with the drug. Similarly, in patient material, CD133 methylation percentage correlated inversely with the protein expression and reflected tumor size with hypermethylation in small (<2 cm) tumors and virtually no methylation in large (>10 cm) GISTs. The gene's methylation percentage and expression level were clearly specific to anatomic sites and distinct driver mutations. KIT -mutant gastric GISTs exhibited significantly lower methylation degrees and concomitant high CD133 protein abundance compared with KIT -mutant GISTs from the small intestine. CD133 hypermethylation was documented in PDGFRA -mutant gastric GISTs along with low CD133 expression compared with KIT -mutant gastric GISTs. High CD133 expression was a prognosticator of shorter disease-free survival in all patients. In a subgroup of KIT -mutant gastric GISTs, low CD133 methylation degree was correlated with a shorter disease-free survival.

CONCLUSIONS

Our results strongly suggest epigenetic regulation of CD133 expression by promoter methylation in GISTs. Pending further validation studies, high abundance of the protein can serve as a marker for malignant GISTs.

Stem Cell Differentiation Stage Factors from Zebrafish Embryo: A Novel Strategy to Modulate the Fate of Normal and Pathological Human (Stem) Cells

In spite of the growing body of evidence on the biology of the Zebrafish embryo and stem cells, including the use of Stem Cell Differentiation Stage Factors (SCDSFs) taken from Zebrafish embryo to impact cancer cell dynamics, comparatively little is known about the possibility to use these factors to modulate the homeostasis of normal human stem cells or to modulate the behavior of cells involved in different pathological conditions. In the present review we recall in a synthetic way the most important researches about the use of SCDSFs in reprogramming cancer cells and in modulating the high speed of multiplication of keratinocytes which is characteristic of some pathological diseases like psoriasis. Moreover we add here the results about the capability of SCDSFs in modulating the homeostasis of human adiposederived stem cells (hASCs) isolated from a fat tissue obtained with a novel-non enzymatic method and device. In addition we report the data not yet published about a first protein analysis of the SCDSFs and about their role in a pathological condition like neurodegeneration.

Cytokine-induced killer cells induce apoptosis and inhibit the Akt/nuclear factor-κB signaling pathway in cisplatin-resistant human glioma U87MG cells

Despite advances in the development of treatment methods, glioma remains among the cancer types with a high rate of mortality. Therefore, significant efforts are made to develop novel strategies for the treatment of glioma. Ineffective, long-term cancer chemotherapy can lead to multidrug resistance (MDR), which is one of the most common reasons for the failure of chemotherapy. The present study investigated the effects of cytokine‑induced killer cells (CIK) on reversing MDR in cisplatin-resistant U87MG cells (U87MG/DDP). Mononuclear cells were isolated from the peripheral blood of healthy individuals and cultured in vitro in the presence of a combination of cytokines to generate CIK for the treatment of U87MG/DDP. An MTS assay, flow cytometric analysis of apoptosis, ELISA, western blotting and reverse transcription quantitative polymerase chain reaction were used to investigate the MDR-reversing effects of CIK as well as the underlying mechanisms. The results showed that cisplatin sensitivity and the apoptotic rate following cisplatin treatment were increased, P‑glycoprotein expression was decreased and the intracellular rhodamine‑123 content was increased in U87MG/DDP co‑cultured with CIK. In addition, the present study also identified increased mRNA and protein expression levels of MDR gene 1 (MDR1), MDR‑associated protein 1 (MRP1), B-cell lymphoma 2, Survivin and glutathione S-transferase‑π, while the phosphorylation of AKT and the transcriptional activity of nuclear factor‑κB in CIK co‑cultured U87MG/DDP was decreased. These results indicated that pre‑treatment with CIK reversed the MDR of U87MG/DDP, and that CIK‑induced apoptosis of U87MG/DDP was associated with the inhibition of Akt/NF‑κB. These findings suggested that treatment with CIK may be an effective method to enhance the sensitivity of patients with glioma to chemotherapy.

Process of the Functional Reorganization of the Cortical Centers for Movement in GBM Patients: fMRI Study

Purpose

The aim of this study was to verify whether the functional reorganization of motor cortex is associated with the increase in the size of WHO type IV glioma lesion, that is, disease duration and development, and whether surgical treatment has an impact on cerebral plasticity.

Methods

The study included 16 patients with primary tumors of the brain located at the region of central sulcus. The clinical status of patients and tumor volume was determined. Functional magnetic resonance imaging examinations were performed before and 3 months after operation.

Results

The activity of all cortical centers, both contralateral and ipsilateral, was observed in a group of small as well as large tumors. The intensity of activation and the number of activated clusters of small tumors were almost always higher as compared with the large tumors. The frequency of the activity of contralateral areas was similar during the first and the second examination. In the case of ipsilateral centers, the frequency of activation during the second examination was lower. Mean values of t-statistics during the first examination were higher than during the second examination. Supplementary motor area (SMAa) was the only center for which the mean values of activation intensity remained similar.

Conclusions

SMAa seems to play the most important role in the processes of motor cortex plasticity in high-grade glioma patients. Surgery seems not having a significant influence on the pattern of functional reorganization of the cortical centers for movement. Identification of the individual patterns of the reorganization of motor centers plays an important role in clinical practice.

MiR-34a regulates blood-tumor barrier function by targeting protein kinase Cε

It is shown for the first time that overexpression of miR-34a increases blood–tumor barrier permeability by targeting PKCε, which is activated by p-PKCε and directly regulates the expression of tight junction–related proteins.

MicroRNA-34a (miR-34a) functions to regulate protein expression at the posttranscriptional level by binding the 3′ UTR of target genes and regulates functions of vascular endothelial cells. However, the role of miR-34a in regulating blood–tumor barrier (BTB) permeability remains unknown. In this study, we show that miR-34a overexpression leads to significantly increased permeability of BTB, whereas miR-34a silencing reduces the permeability of the BTB. In addition, miR-34a overexpression significantly down-regulates the expression and distribution of tight junction–related proteins in glioma endothelial cells (GECs), paralleled by protein kinase Cε (PKCε) reduction. Moreover, luciferase reporter gene analysis shows that PKCε is the target gene of miR-34a. We also show that cotransfection of miR-34a and PKCε inversely coregulates BTB permeability and protein expression levels of tight junction–related proteins. Pretreatment of ψεRACK, a PKCε-specific activator, decreases BTB permeability in miR-34a–overexpressed GECs and up-regulates expression levels of tight junction proteins. In contrast, pretreatment of εV1-2, a specific PKCε inhibitor, gives opposite results. Collectively, our findings indicate that miR-34a regulates BTB function by targeting PKCε; after phosphorylation, PKCε is activated and contributes to regulation of the expression of tight junction–related proteins, ultimately altering BTB permeability.

TRPM7 channels regulate glioma stem cell through STAT3 and Notch signaling pathways

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in adults with median survival time of 14.6 months. A small fraction of cancer stem cells (CSC) initiate and maintain tumors thus driving glioma tumorigenesis and being responsible for resistance to classical chemo- and radio-therapies. It is desirable to identify signaling pathways related to CSC to develop novel therapies to selectively target them. Transient receptor potential cation channel, subfamily M, member 7, also known as TRPM7 is a ubiquitous, Ca(2+) and Mg(2+) permeable ion channels that are special in being both an ion channel and a serine/threonine kinase. In studies of glioma cells silenced for TRPM7, we demonstrated that Notch (Notch1, JAG1, Hey2, and Survivin) and STAT3 pathways are down regulated in glioma cells grown in monolayer. Furthermore, phospho-STAT3, Notch target genes and CSC markers (ALDH1 and CD133) were significantly higher in spheroid glioma CSCs when compared with monolayer cultures. The results further show that tyrosine-phosphorylated STAT3 binds and activates the ALDH1 promoters in glioma cells. We found that TRMP7-induced upregulation of ALDH1 expression is associated with increases in ALDH1 activity and is detectable in stem-like cells when expanded as spheroid CSCs. Finally, TRPM7 promotes proliferation, migration and invasion of glioma cells. These demonstrate that TRPM7 activates JAK2/STAT3 and/or Notch signaling pathways and leads to increased cell proliferation and migration. These findings for the first time demonstrates that TRPM7 (1) activates a previously unrecognized STAT3→ALDH1 pathway, and (2) promotes the induction of ALDH1 activity in glioma cells.

Vaccine therapies for patients with glioblastoma

Glioblastoma (GBM) is a high-grade glial tumor with an extremely aggressive clinical course and a median overall survival of only 14.6 months following maximum surgical resection and adjuvant chemoradiotherapy. A central feature of this disease is local and systemic immunosuppression, and defects in patient immune systems are closely associated with tumor progression. Immunotherapy has emerged as an important adjuvant in the therapeutic armamentarium of clinicians caring for patients with GBM. The fundamental aim of immunotherapy is to augment the host antitumor immune response. Active immunotherapy utilizes vaccines to stimulate adaptive immunity against tumor-associated antigens. A vast array of vaccine strategies have advanced from preclinical study to active clinical trials in patients with recurrent or newly diagnosed GBM, including those that employ peptides, heat shock proteins, autologous tumor cells, and dendritic cells. In this review, the rationale for glioma immunotherapy is outlined, and the prevailing forms of vaccine therapy are described.

Therapeutic potential of targeting glucose metabolism in glioma stem cells

Glioblastoma is a highly lethal cancer. Glioma stem cells (GSCs) are potentially an attractive therapeutic target and eradication of GSCs may impact tumor growth and sensitize tumors to conventional therapies. The brain is one of the most metabolically active organs with glucose representing the most important, but not the only, source of energy and carbon. Like all other cancers, glioblastoma requires a continuous source of energy and molecular resources for new cell production with a preferential use of aerobic glycolysis, recognized as the Warburg effect. As selected metabolic nodes are amenable to therapeutic targeting, we observed that the Warburg effect may causally contribute to glioma heterogeneity. This Editorial summarizes recent studies that examine the relationship between GSCs and metabolism and briefly provides our views for the future directions. The ultimate goal is to establish a new concept by incorporating both the cellular hierarchical theory and the cellular evolution theory to explain tumor heterogeneity. Such concept may better elucidate the mechanisms of how tumors gain cellular and molecular complexity and guide us develop novel and effective targeted therapies.

MiR-330-mediated regulation of SH3GL2 expression enhances malignant behaviors of glioblastoma stem cells by activating ERK and PI3K/AKT signaling pathways

MicroRNAs are currently considered as an active and rapidly evolving area for the treatment of tumors. In this study, we elucidated the biological significance of miR-330 in glioblastoma stem cells (GSCs) as well as the possible molecular mechanisms. SH3GL2 is mainly distributed in the central nervous system and considered to be a tumor suppressor in many tumors. In the present study, we identified miR-330 as a potential regulator of SH3GL2 and we found that it was to be inversely correlated with SH3GL2 expression in GSCs which were isolated from U87 cell lines. The expression of miR-330 enhanced cellular proliferation, promoted cell migration and invasion, and dampened cell apoptosis. When the GSCs were co-transfected with the plasmid containing short hairpin RNA directed against human SH3GL2 gene and miR-330 mimic, we found that miR-330 promoted the malignant behavior of GSCs by down-regulating the expression of SH3GL2. Meanwhile, the ERK and PI3K/AKT signaling pathways were significantly activated, leading to the decreased expression of apoptotic protein and increased expression of anti-apoptotic protein. Furthermore, in orthotopic mouse xenografts, the mice given stable over-expressed SH3GL2 cells co-transfected with miR-330 knockdown plasmid had the smallest tumor sizes and longest survival. In conclusion, these results suggested that miR-330 negatively regulated the expression of SH3GL2 in GSCs, which promoted the oncogenic progression of GSCs through activating ERK and PI3K/AKT signaling pathways. The elucidation of these mechanisms will provide potential therapeutic approaches for human glioblastoma.

Targeting cancer stem cells for treatment of glioblastoma multiforme

Cancer stem cells (CSCs) in glioblastoma multiforme (GBM) are radioresistant and chemoresistant, which eventually results in tumor recurrence. Targeting CSCs for treatment is the most crucial issue. There are five methods for targeting the CSCs of GBM. One is to develop a new chemotherapeutic agent specific to CSCs. A second is to use a radiosensitizer to enhance the radiotherapy effect on CSCs. A third is to use immune cells to attack the CSCs. In a fourth method, an agent is used to promote CSCs to differentiate into normal cells. Finally, ongoing gene therapy may be helpful. New therapeutic agents for targeting a signal pathway, such as epidermal growth factor (EGF) and vascular epidermal growth factor (VEGF) or protein kinase inhibitors, have been used for GBM but for CSCs the effects still require further evaluation. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as cyclooxygenase-2 (Cox-2) inhibitors have proven to be effective for increasing radiation sensitivity of CSCs in culture. Autologous dendritic cells (DCs) are one of the promising immunotherapeutic agents in clinical trials and may provide another innovative method for eradication of CSCs. Bone-morphogenetic protein 4 (BMP4) is an agent used to induce CSCs to differentiate into normal glial cells. Research on gene therapy by viral vector is also being carried out in clinical trials. Targeting CSCs by eliminating the GBM tumor may provide an innovative way to reduce tumor recurrence by providing a synergistic effect with conventional treatment. The combination of conventional surgery, chemotherapy, and radiotherapy with stem cell-orientated therapy may provide a new promising treatment for reducing GBM recurrence and improving the survival rate.

Immune cell infiltrates in atypical teratoid/rhabdoid tumors

OBJECTIVE

Atypical teratoid/rhabdoid tumor (AT/RT) is a highly malignant tumor of the central nervous system. Its pathogenesis remains unknown. Like glioblastomas, AT/RTs contain brain cancer stem cells (CSCs) that suppress the immunity of patients and are resistant to conventional chemotherapy and radiation therapy. Considerable infiltration of immune cells, including macrophages/microglia, dendritic cells and T-cells, has been noted in glioblastomas, which correlates with poor prognosis. The present study examines the significance of infiltrating immune cells in four cases of AT/RT; including one associated with an autoimmune disease, Henoch-Schonlein purpura.

METHODS

Tumor tissues from four patients with AT/RT were analyzed and compared with those from four patients with glioblastomas. The frequency of immune cells, including CD68+, CD4+, and CD8+ cells, was assessed by scoring for statistical analysis.

RESULTS

The infiltration of immune cells was identified in the case of AT/RT associated with HSP and three other cases of infratentorial AT/RTs. Moderate infiltration of CD68+ macrophages/microglia and CD4+ cells was noted in AT/RTs with no significant difference from that in glioblastomas (p > 0.05). However, the infiltration of CD8+ T-cells was significantly higher in AT/RTs than that in glioblastomas (p < 0.05); CD4+/CD8+ ratio was significantly lower in AT/RTs than that in glioblastomas (p < 0.05). In addition, eosinophils were found in all AT/RTs, but not in glioblastomas.

CONCLUSIONS

These findings suggest an immune microenvironment of AT/RTs with more immune effectors than glioblastomas. Our observation contributes to understanding the growth environment of AT/RTs for which adjuvant immunotherapy may be potentially beneficial.

CD133 as a marker for regulation and potential for targeted therapies in glioblastoma multiforme

The CD133 epitope has been identified as a tumor marker for the purification of a subpopulation of glioblastoma multiforme (GBM) cells demonstrating cancer stem cell phenotypes. Isolated tumorsphere-forming CD133(+) GBM cells demonstrated heightened in vitro proliferation, self-renewal, and invasive capacity. Orthotopic transplantation of CD133(+) cells led to the formation of heterogeneous tumors that were phenocopies of the original patient tumor. In this article, the authors discuss the complex regulation of CD133 expression in gliomas, its role in tumorigenesis, and its potential as a marker for targeted and personalized therapeutic intervention.

Immunotherapy: a useful strategy to help combat multidrug resistance

Multidrug resistance (MDR) renders cancer cells relatively invulnerable to treatment with many standard cytotoxic anti-cancer agents. Cancer immunotherapy could be an important adjunct for other strategies to treat MDR positive cancers, as resistance to immunotherapy generally is unrelated to mechanisms of resistance to cytotoxic agents. Immunotherapy to combat MDR positive tumors could use any of the following strategies: direct immune attack against MDR positive cells, using MDR as an immune target to deliver cytotoxic agents, capitalization on other immune properties of MDR positive cells, or conditional immunotoxins expressed under MDR control. Additional insights into the immunogenic potential of some cytotoxic agents can also be brought to bear on these strategies. This review will highlight key concepts in cancer immunotherapy and illustrate immune principles and strategies that have been or could be used to help destroy MDR positive tumor cells, either alone or in rational combinations.

Stem-like tumor-initiating cells isolated from IL13Rα2 expressing gliomas are targeted and killed by IL13-zetakine-redirected T Cells

PURPOSE

To evaluate IL13Rα2 as an immunotherapeutic target for eliminating glioma stem-like cancer initiating cells (GSC) of high-grade gliomas, with particular focus on the potential of genetically engineered IL13Rα2-specific primary human CD8(+) CTLs (IL13-zetakine(+) CTL) to target this therapeutically resistant glioma subpopulation.

EXPERIMENTAL DESIGN

A panel of low-passage GSC tumor sphere (TS) and serum-differentiated glioma lines were expanded from patient glioblastoma specimens. These glioblastoma lines were evaluated for expression of IL13Rα2 and for susceptibility to IL13-zetakine(+) CTL-mediated killing in vitro and in vivo.

RESULTS

We observed that although glioma IL13Rα2 expression varies between patients, for IL13Rα2(pos) cases this antigen was detected on both GSCs and more differentiated tumor cell populations. IL13-zetakine(+) CTL were capable of efficient recognition and killing of both IL13Rα2(pos) GSCs and IL13Rα2(pos) differentiated cells in vitro, as well as eliminating glioma-initiating activity in an orthotopic mouse tumor model. Furthermore, intracranial administration of IL13-zetakine(+) CTL displayed robust antitumor activity against established IL13Rα2(pos) GSC TS-initiated orthotopic tumors in mice.

CONCLUSIONS

Within IL13Rα2 expressing high-grade gliomas, this receptor is expressed by GSCs and differentiated tumor populations, rendering both targetable by IL13-zetakine(+) CTLs. Thus, our results support the potential usefullness of IL13Rα2-directed immunotherapeutic approaches for eradicating therapeutically resistant GSC populations.

Immunotherapy targeting glioma stem cells--insights and perspectives

INTRODUCTION

Glioblastoma multiforme (GBM) is the most aggressive and lethal primary malignant brain tumor. Although progress has been made in current conventional therapies for GBM patients, the effect of these advances on clinical outcomes has been disappointing. Recent research into the origin of cancers suggest that GBM cancer stem cells (GSC) are the source of initial tumor formation, resistance to current conventional therapeutics and eventual patient relapse. Currently, there are very few studies that apply immunotherapy to target GSC.

AREAS COVERED

CD133, a cell surface protein, is used extensively as a surface marker to identify and isolate GSC in malignant glioma. We discuss biomarkers such as CD133, L1-cell adhesion molecule (L1-CAM), and A20 of GSC. We review developing novel treatment modalities, including immunotherapy strategies, to target GSC.

EXPERT OPINION

There are very few reports of preclinical studies targeting GSC. Identification and validation of unique molecular signatures and elucidation of signaling pathways involved in survival, proliferation and differentiation of GSC will significantly advance this field and provide a framework for the rational design of a new generation of antigen-specific, anti-GSC immunotherapy- and nanotechnology-based targeted therapyies. Combined with other therapeutic avenues, GSC-targeting therapies may represent a new paradigm to treat GBM patients.