Glioblastomas induce T-lymphocyte death by two distinct pathways involving gangliosides and CD70

Immune Evasion Strategies of Glioblastoma

Glioblastoma (GBM) is the most devastating brain tumor, with associated poor prognosis. Despite advances in surgery and chemoradiation, the survival of afflicted patients has not improved significantly in the past three decades. Immunotherapy has been heralded as a promising approach in treatment of various cancers; however, the immune privileged environment of the brain usually curbs the optimal expected response in central nervous system malignancies. In addition, GBM cells create an immunosuppressive microenvironment and employ various methods to escape immune surveillance. The purpose of this review is to highlight the strategies by which GBM cells evade the host immune system. Further understanding of these strategies and the biology of this tumor will pave the way for developing novel immunotherapeutic approaches for treatment of GBM.

Melanoma Expressed-CD70 Is Regulated by RhoA and MAPK Pathways without Affecting Vemurafenib Treatment Activity

CD70 is a costimulatory molecule member of the Tumor Necrosis Factor family that is expressed on activated immune cells. Its ectopic expression has been described in several types of cancer cells including lymphomas, renal cell carcinomas and glioblastomas. We have recently described its expression in a part of tumor cells from the vast majority of melanoma biopsies and human melanoma cell lines, and found that CD70 expression decreased over time as the disease progressed. Here, we show that RhoA, BRAF and Mitogen Activating Protein Kinase pathways are involved in the positive transcriptional regulation of CD70 expression in melanomas. Interestingly, the clinical inhibitor of the common BRAF V600E/D variants, Vemurafenib (PLX-4032), which is currently used to treat melanoma patients with BRAF V600E/D-mutated metastatic melanomas, decreased CD70 expression in human CD70+ melanoma cell lines. This decrease was seen in melanoma cells both with and without the BRAFV600E/D mutation, although was less efficient in those lacking the mutation. But interestingly, by silencing CD70 in CD70+ melanoma cell lines we show that PLX-4032-induced melanoma cell killing and its inhibitory effect on MAPK pathway activation are unaffected by CD70 expression. Consequently, our work demonstrates that CD70 ectopic expression in melanomas is not a valuable biomarker to predict tumor cells sensitivity to BRAF V600 inhibitors.

pVHL/HIF-regulated CD70 expression is associated with infiltration of CD27+ lymphocytes and increased serum levels of soluble CD27 in clear cell renal cell carcinoma

PURPOSE

CD70, a member of the TNF ligand superfamily, has been shown frequently overexpressed in clear cell renal cell carcinoma (ccRCC). The mechanisms of CD70's upregulation and its role in ccRCC are unknown.

EXPERIMENTAL DESIGN

CD70 expression was immunohistochemically analyzed in 667 RCCs and RCC metastases. Von Hippel-Lindau gene (VHL) mutations, expression patterns of VHL protein (pVHL), hypoxia-inducible factor (HIF) α, and several HIF targets were studied in tissues and cell lines and correlated with CD70 overexpression. Gene promoter analysis was performed to confirm CD70 as HIF target gene. Consecutive tissue sections were immunostained to reveal the relation between CD70-expressing RCCs and tumor-infiltrating lymphocytes positive for the CD70 receptor (CD27). CD70-mediated release of soluble CD27 in RCC was assessed by coculture experiments and sera analysis of patients with RCC.

RESULTS

Elevated CD70 expression was seen in 80% of primary tumors and metastases of ccRCC and correlated with dysregulation of the pVHL/HIF pathway. In vitro analyses demonstrated that CD70 upregulation is driven by HIF. Furthermore, CD27(+) lymphocytes preferentially infiltrate CD70-expressing ccRCCs. CD70-dependent release of soluble CD27 in cocultures may explain the high CD27 levels observed in sera of patients with CD70-expressing ccRCC. The combination of lymphocyte infiltration and CD70 expression in RCC was associated with worse patient outcome.

CONCLUSION

Our findings demonstrate that in ccRCC, CD70 expression is regulated by HIF as a consequence of pVHL inactivation. Increased serum levels of CD27 suggest the existence of CD70-expressing ccRCC, thus representing a potential serum marker for patients suffering from this disease.

Characterization of the human T cell response to in vitro CD27 costimulation with varlilumab

Background

Clinical targeting of TNFR family of receptors (CD40, CD134 and CD137) with immunostimulatory monoclonal antibodies has been successful in cancer immunotherapy. However, targeting of CD27 with a mAb is a relatively new approach to provide costimulation of immune cells undergoing activation. Thus, activation of human CD27 (TNFRSF7) with a monoclonal antibody (varlilumab) has previously been demonstrated to result in T cell activation and anti-tumor activity in preclinical models, and is currently in early phase clinical trials in patients with advanced malignancies. In this study we used an in vitro system using human peripheral blood T cells to characterize the varlilumab-mediated costimulatory effects in combination with TCR stimulation in terms of phenotypic, transcriptional and functionality changes.

Methods

T cells were isolated from normal volunteer PBMCs using magnetic bead isolation kits and stimulated in vitro with plate bound anti-CD3 Ab (OKT3) and varlilumab or control Ab for 72 h. Activation profiles were monitored by ELISA or Luminex-based testing cytokine/chemokine releases, cell surface phenotyping for costimulatory and coinhibitory markers and CFSE dye dilution by proliferating T cells and Tregs. Changes in gene expression and transcriptome analysis of varlilumab-stimulated T cells was carried on Agilent Human whole genome microarray datasets using a suite of statistical and bioinformatic software tools.

Results

Costimulation of T cells with varlilumab required continuous TCR signaling as pre-activated T cells were unable to produce cytokines with CD27 signaling alone. Analysis of T cell subsets further revealed that memory CD4+ and CD8+ T cells were specifically activated with a bias toward CD8+ T lymphocyte proliferation. Activation was accompanied by upregulated cell surface expression of costimulatory [4-1BB, OX40, GITR and ICOS] and coinhibitory [PD-1] molecules. Importantly, varlilumab costimulation did not activate purified Tregs as measured by cytokine production, proliferation and suppression of dividing non-Treg T cells. Analysis of changes in gene expression during varlilumab stimulation of T cells revealed modulation of pro-inflammatory signatures consistent with cellular activation and proliferation, with the IL-2 pathway showing the highest frequency of gene modulation.

Conclusions

Altogether, the data reveal the requirements and T cell subtype-specific effects of CD27 costimulation, and helps select relevant biomarkers for studying the effects of varlilumab in patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-015-0080-2) contains supplementary material, which is available to authorized users.

GBM Derived Gangliosides Induce T Cell Apoptosis through Activation of the Caspase Cascade Involving Both the Extrinsic and the Intrinsic Pathway

Previously we demonstrated that human glioblastoma cell lines induce apoptosis in peripheral blood T cells through partial involvement of secreted gangliosides. Here we show that GBM-derived gangliosides induce apoptosis through involvement of the TNF receptor and activation of the caspase cascade. Culturing T lymphocytes with GBM cell line derived gangliosides (10-20μg/ml) demonstrated increased ROS production as early as 18 hrs as indicated by increased uptake of the dye H₂DCFDA while western blotting demonstrated mitochondrial damage as evident by cleavage of Bid to t-Bid and by the release of cytochrome-c into the cytosol. Within 48-72 hrs apoptosis was evident by nuclear blebbing, trypan blue positivity and annexinV/7AAD staining. GBM-ganglioside induced activation of the effector caspase-3 along with both initiator caspases (-9 and -8) in T cells while both the caspase-8 and -9 inhibitors were equally effective in blocking apoptosis (60% protection) confirming the role of caspases in the apoptotic process. Ganglioside-induced T cell apoptosis did not involve production of TNF-α since anti-human TNFα antibody was unable to protect T cells from nuclear blebbing and subsequent cell death. However, confocal microscopy demonstrated co-localization of GM2 ganglioside with the TNF receptor and co-immunoprecipitation experiments showed recruitment of death domains FADD and TRADD with the TNF receptor post ganglioside treatment, suggesting direct interaction of gangliosides with the TNF receptor. Further confirmation of the interaction between GM2 and TNFR1 was obtained from confocal microscopy data with wild type and TNFR1 KO (TALEN mediated) Jurkat cells, which clearly demonstrated co-localization of GM2 and TNFR1 in the wild type cells but not in the TNFR1 KO clones. Thus, GBM-ganglioside can mediate T cell apoptosis by interacting with the TNF receptor followed by activation of both the extrinsic and the intrinsic pathway of caspases.

Clinical significance of CD70 expression on T cells in human T-lymphotropic virus type-1 carriers and adult T cell leukemia/ lymphoma patients

Human T-lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma (ATL). Miscellaneous host immune surveillance systems control T-cell growth/leukemogenesis during HTLV-1 infection. We characterized CD70 and CD27 expression on lymphocytes of HTLV-1 carriers and patients with ATL (study approved by the local Medical Ethical Committee). High CD70 expression was observed on CD4 + CD25+ T cells from patients with acute-type ATL, while patients with smoldering- or chronic-type ATL and HTLV-1 carriers exhibited lower expression. Furthermore, significantly higher CD27 expression was observed on HTLV-1-specific CTLs. We found an association between CD70 expression on CD4 + T cells and HTLV-1 infection; increased CD70 expression was observed after exposure to Tax. Moreover, addition of anti-CD70 antibodies enhanced the CD107a surface mobilization of HTLV-1 Tax-specific CTLs following Tax-peptide stimulation in the PBMCs of carriers. These data demonstrate the important role of the CD70/CD27 axis in immune responses in HTLV-1 carriers and ATL patients.

The ganglioside GM3 is associated with cisplatin-induced apoptosis in human colon cancer cells

Cisplatin (cis-diamminedichloroplatinum, CDDP) is a well-known chemotherapeutic agent for the treatment of several cancers. However, the precise mechanism underlying apoptosis of cancer cells induced by CDDP remains unclear. In this study, we show mechanistically that CDDP induces GM3-mediated apoptosis of HCT116 cells by inhibiting cell proliferation, and increasing DNA fragmentation and mitochondria-dependent apoptosis signals. CDDP induced apoptosis within cells through the generation of reactive oxygen species (ROS), regulated the ROS-mediated expression of Bax, Bcl-2, and p53, and induced the degradation of the poly (ADP-ribosyl) polymerase (PARP). We also checked expression levels of different gangliosides in HCT116 cells in the presence or absence of CDDP. Interestingly, among the gangliosides, CDDP augmented the expression of only GM3 synthase and its product GM3. Reduction of the GM3 synthase level through ectopic expression of GM3 small interfering RNA (siRNA) rescued HCT116 cells from CDDP-induced apoptosis. This was evidenced by inhibition of apoptotic signals by reducing ROS production through the regulation of 12-lipoxigenase activity. Furthermore, the apoptotic sensitivity to CDDP was remarkably increased in GM3 synthase-transfected HCT116 cells compared to that in controls. In addition, GM3 synthase-transfected cells treated with CDDP exhibited an increased accumulation of intracellular ROS. These results suggest the CDDP-induced oxidative apoptosis of HCT116 cells is mediated by GM3.

TGF-β upregulates CD70 expression and induces exhaustion of effector memory T cells in B-cell non-Hodgkin's lymphoma

Transforming growth factor beta (TGF-β) has an important role in mediating T-cell suppression in B-cell non-Hodgkin lymphoma (NHL). However, the underlying mechanism responsible for TGF-β-mediated inhibition of effector memory T (Tm) cells is largely unknown. As reported here, we show that exhaustion is a major mechanism by which TGF-β inhibits Tm cells, and TGF-β mediated exhaustion is associated with upregulation of CD70. We found that TGF-β upregulates CD70 expression on effector Tm cells while it preferentially induces Foxp3 expression in naive T cells. CD70 induction by TGF-β is Smad3-dependent and involves IL-2/Stat5 signaling. CD70+ T cells account for TGF-β-induced exhaustion of effector Tm cells. Both TGF-β-induced and preexisting intratumoral CD70+ effector Tm cells from B-cell NHL have an exhausted phenotype and express higher levels of PD-1 and TIM-3 compared with CD70- T cells. Signaling transduction, proliferation and cytokine production are profoundly decreased in these cells, and they are highly susceptible to apoptosis. Clinically, intratumoral CD70-expressing T cells are prevalent in follicular B-cell lymphoma (FL) biopsy specimens, and increased numbers of intratumoral CD70+ T cells correlate with an inferior patient outcome. These findings confirm TGF-β-mediated effector Tm cell exhaustion as an important mechanism of immune suppression in B-cell NHL.

The costimulatory molecule CD70 is regulated by distinct molecular mechanisms and is associated with overall survival in diffuse large B-cell lymphoma

In diffuse large B-cell lymphomas (DLBCL), a recurrent deletion of the 19p13 region has recently been described. CD70 and TNFSF9 genes are suspected tumor suppressor genes, but previous studies suggest an oncogenic role for CD70. Therefore, we studied the consequences of variation in CD70 copy number and epigenetic modifications on CD70 expression. Copy-number variation was investigated in 144 de novo DLBCL tissues by comparative genomic hybridization array and quantitative multiplex PCR. Gene expression was assessed by quantitative RT-PCR, and CD70 promoter methylation was determined by pyrosequencing. The 19p13.3.2 region was deleted in 21 (14.6%) cases, which allowed the minimal commonly deleted region of 57 Kb that exclusively includes the CD70 gene to be defined. Homozygous deletions were observed in four (2.7%) cases, and acquired single-nucleotide variations of CD70 were detected in nine (6.3%) cases. CD70 was highly expressed in both germinal centre B-cell-like (GCB) and activated B-cell-like (ABC) DLBCL compared to normal tissue, with distinct molecular mechanisms of mRNA expression regulation. A gene dosage effect was observed in the GCB subtype, whereas promoter methylation was the predominant mechanism of down regulation in the ABC subtype. However, high CD70 expression levels correlated to shorter overall survival in both the GCB (P = 0.0021) and the ABC (P =0.0158) subtypes. In conclusion, CD70 is targeted by recurrent deletions, somatic mutations and promoter hypermethylation, but its high level of expression is related to an unfavorable outcome, indicating that this molecule may constitute a potential therapeutic target in selected DLBCL.

CD70-CD27 ligation between neural stem cells and CD4+ T cells induces Fas-FasL-mediated T-cell death

INTRODUCTION

Neural stem cells (NSCs) are among the most promising candidates for cell replacement therapy in neuronal injury and neurodegenerative diseases. One of the remaining obstacles for NSC therapy is to overcome the alloimmune response on NSCs by the host.

METHODS

To investigate the mechanisms of immune modulatory function derived from the interaction of human NSCs with allogeneic T cells, we examined the immune regulatory effects of human NSCs on allogeneic T cells in vitro.

RESULTS

Significantly, NSCs induced apoptosis of allogeneic T cells, in particular CD4+ T cells. Interaction of CD70 on NSCs and CD27 on CD4(+) T cells mediated apoptosis of T cells. Thus, blocking CD70-CD27 interaction prevented NSC-mediated death of CD4(+) T cells.

CONCLUSIONS

We present a rational explanation of NSC-induced immune escape in two consecutive stages. First, CD70 constitutively expressed on NSCs engaged CD27 on CD4(+) T cells, which induced Fas ligand expression on CD4(+) T cells. Second, CD4(+) T-cell apoptosis was followed by Fas-Fas ligand interaction in the CD4(+) T cells.

Gliomas promote immunosuppression through induction of B7-H1 expression in tumor-associated macrophages

PURPOSE

Gliomas are known to induce local and systemic immunosuppression, inhibiting T-cell-mediated cytotoxic responses to tumor growth. Tumor-associated macrophages are a significant component of the immune infiltrate in gliomas and may express immunosuppressive surface ligands, such as B7-H1.

EXPERIMENTAL DESIGN

Tumor and peripheral blood samples from patients with glioblastoma (GBM) were analyzed by flow cytometry to evaluate the expression of B7-H1 in circulating and tumor-infiltrating macrophages. Human monocytes from healthy patients were stimulated with conditioned media from glioma cells to evaluate B7-H1 expression. Production of interleukin (IL)-10 by stimulated monocytes was measured by ELISA, and stimulation with IL-10 alone was evaluated for the ability to induce B7-H1 expression. The effect of inhibiting IL-10 and its receptor on glioma-induced B7-H1 expression in monocytes was evaluated.

RESULTS

Circulating monocytes in patients with GBM had significantly increased expression of B7-H1 compared with healthy control patients. Tumor-associated macrophages from matched GBM tissue had even greater B7-H1 expression. Treatment of normal monocytes with glioma-conditioned media could significantly increase B7-H1 expression. Stimulation of monocytes with conditioned media resulted in substantial production of IL-10 and upregulation of the IL-10 receptor. Stimulation of monocytes with IL-10 alone could significantly increase B7-H1 expression, sufficient to induce T-cell apoptosis when cocultured with stimulated monocytes. Inhibition of IL-10 and the IL-10 receptor could knock down the effect of glioma media on B7-H1 by more than 50%.

CONCLUSIONS

Gliomas can upregulate B7-H1 expression in circulating monocytes and tumor-infiltrative macrophages through modulation of autocrine/paracrine IL-10 signaling, resulting in an immunosuppressive phenotype.

Subtyping glioblastoma by combining miRNA and mRNA expression data using compressed sensing-based approach

In the clinical practice, many diseases such as glioblastoma, leukemia, diabetes, and prostates have multiple subtypes. Classifying subtypes accurately using genomic data will provide individualized treatments to target-specific disease subtypes. However, it is often difficult to obtain satisfactory classification accuracy using only one type of data, because the subtypes of a disease can exhibit similar patterns in one data type. Fortunately, multiple types of genomic data are often available due to the rapid development of genomic techniques. This raises the question on whether the classification performance can significantly be improved by combining multiple types of genomic data. In this article, we classified four subtypes of glioblastoma multiforme (GBM) with multiple types of genome-wide data (e.g., mRNA and miRNA expression) from The Cancer Genome Atlas (TCGA) project. We proposed a multi-class compressed sensing-based detector (MCSD) for this study. The MCSD was trained with data from TCGA and then applied to subtype GBM patients using an independent testing data. We performed the classification on the same patient subjects with three data types, i.e., miRNA expression data, mRNA (or gene expression) data, and their combinations. The classification accuracy is 69.1% with the miRNA expression data, 52.7% with mRNA expression data, and 90.9% with the combination of both mRNA and miRNA expression data. In addition, some biomarkers identified by the integrated approaches have been confirmed with results from the published literatures. These results indicate that the combined analysis can significantly improve the accuracy of classifying GBM subtypes and identify potential biomarkers for disease diagnosis.

Immunotherapy targets in pediatric cancer

Immunotherapy for cancer has shown increasing success and there is ample evidence to expect that progress gleaned in immune targeting of adult cancers can be translated to pediatric oncology. This manuscript reviews principles that guide selection of targets for immunotherapy of cancer, emphasizing the similarities and distinctions between oncogene-inhibition targets and immune targets. It follows with a detailed review of molecules expressed by pediatric tumors that are already under study as immune targets or are good candidates for future studies of immune targeting. Distinctions are made between cell surface antigens that can be targeted in an MHC independent manner using antibodies, antibody derivatives, or chimeric antigen receptors versus intracellular antigens which must be targeted with MHC restricted T cell therapies. Among the most advanced immune targets for childhood cancer are CD19 and CD22 on hematologic malignancies, GD2 on solid tumors, and NY-ESO-1 expressed by a majority of synovial sarcomas, but several other molecules reviewed here also have properties which suggest that they too could serve as effective targets for immunotherapy of childhood cancer.

Reprint of: chip-based nanoelectrospray mass spectrometry of brain gangliosides

In the past few years, a considerable effort was invested in interfacing mass spectrometry (MS) to microfluidics-based systems for electrospray ionization (ESI). Since its first introduction in biological mass spectrometry, chip-based ESI demonstrated a high potential to discover novel structures of biomarker value. Therefore, recently, microfluidics for electrospray in conjunction with advanced MS instruments able to perform multistage fragmentation were introduced also in glycolipid research. This review is focused on the strategies, which allowed a successful application of chip technology for ganglioside mapping and sequencing by ESI MS and tandem MS (MS/MS). The first part of the review is dedicated to the progress of MS methods in brain ganglioside research, which culminated with the introduction of two types of microfluidic devices: the NanoMate robot and a polymer microchip for electrospray. In the second part a systematic description of most relevant results obtained by using MS in combination with the two chip systems is presented. Chip-based ESI accomplishments for determination of ganglioside expression and structure in normal brain regions and brain pathologies such as neurodegenerative diseases and primary brain tumors are described together with some considerations upon the perspectives of microfluidics-MS to be routinely introduced in biomedical investigation.

T cells redirected against CD70 for the immunotherapy of CD70-positive malignancies

T-cell therapy with genetically modified T cells targeting CD19 or CD20 holds promise for the immunotherapy of hematologic malignancies. These targets, however, are only present on B cell-derived malignancies, and because they are broadly expressed in the hematopoietic system, their targeting may have unwanted consequences. To expand T-cell therapies to hematologic malignancies that are not B cell-derived, we determined whether T cells can be redirected to CD70, an antigen expressed by limited subsets of normal lymphocytes and dendritic cells, but aberrantly expressed by a broad range of hematologic malignancies and some solid tumors. To generate CD70-specific T cells, we constructed a chimeric antigen receptor (CAR) consisting of the CD70 receptor (CD27) fused to the CD3-ζ chain. Stimulation of T cells expressing CD70-specific CARs resulted in CD27 costimulation and recognition of CD70-positive tumor cell lines and primary tumor cells, as shown by IFN-γ and IL-2 secretion and by tumor cell killing. Adoptively transferred CD70-specific T cells induced sustained regression of established murine xenografts. Therefore, CD70-specific T cells may be a promising immunotherapeutic approach for CD70-positive malignancies.

Overview of cellular immunotherapy for patients with glioblastoma

High grade gliomas (HGG) including glioblastomas (GBM) are the most common and devastating primary brain tumours. Despite important progresses in GBM treatment that currently includes surgery combined to radio- and chemotherapy, GBM patients' prognosis remains very poor. Immunotherapy is one of the new promising therapeutic approaches that can specifically target tumour cells. Such an approach could also maintain long term antitumour responses without inducing neurologic defects. Since the past 25 years, adoptive and active immunotherapies using lymphokine-activated killer cells, cytotoxic T cells, tumour-infiltrating lymphocytes, autologous tumour cells, and dendritic cells have been tested in phase I/II clinical trials with HGG patients. This paper inventories these cellular immunotherapeutic strategies and discusses their efficacy, limits, and future perspectives for optimizing the treatment to achieve clinical benefits for GBM patients.

Distinct effects of human glioblastoma immunoregulatory molecules programmed cell death ligand-1 (PDL-1) and indoleamine 2,3-dioxygenase (IDO) on tumour-specific T cell functions

Immunotherapy is a promising new treatment for patients suffering from glioma, in particular glioblastoma multiforme (GBM). However, tumour cells use different mechanisms to escape the immune responses induced by the treatment. As many other tumours, gliomas express or secrete several immunosuppressive molecules that regulate immune cell functions. In this study, we first analysed FasL, HLA-G, IDO, PDL-1 and TGF-beta1, -beta2 and -beta3 expression by transcriptomic microarray analysis in a series of 20 GBM samples and found respectively 15%, 60%, 85%, 30%, 70%, 80% and 35% of positive specimens. mRNA expression was then confirmed in 10 GBM primary cell lines and 2 immortalised cell lines U251 and U87MG. Furthermore, the protein expression of PDL-1, IDO activity and TGF-beta2 secretion were found on most of the untreated GBM primary cell lines. Remarkably, treatment with IFN-gamma increased the PDL-1 cell surface expression and the IDO activity, but reduced the TGF-beta2 secretion of GBM cell lines. We finally analysed the immunosuppressive effects of IDO, PDL-1 and TGF-beta1-3 by measuring IFN-gamma production and cell cytotoxicity activity of tumour antigen-specific T cells. PDL-1 partially affected the IFN-gamma production of antigen-specific T cells in response to GBM primary cell lines, and IDO inhibited lymphocyte proliferation induced by lectins. None of these molecules directly affected the T cell cytotoxicity function. Due to the functional role of PDL-1 and IDO molecules expressed by GBM cells, one could expect that blocking these molecules in the immunotherapy strategies would reinforce the efficiency of these treatments of GBM patients.

Elevated levels of select gangliosides in T cells from renal cell carcinoma patients is associated with T cell dysfunction

Increased expression of gangliosides by different tumor types including renal cell carcinoma (RCC) is thought to contribute to the immune suppression observed in cancer patients. In this study, we report an increase in apoptotic T cells from RCC patients compared with T cells from normal donors that coincided with the detection of T cells staining positive for GM2 and that the apoptosis was predominantly observed in the GM2(+) but not the GM2(-) T cell population. Ganglioside shedding from tumor rather than endogenous production accounts for GM2(+) T cells since there was no detectable level of mRNA for GM2 synthase in RCC patient T cells and in T cells from normal healthy donors after incubation with either purified GM2 or supernatant from RCC cell lines despite their staining positive for GM2. Moreover, reactive oxygen species as well as activated caspase 3, 8, and 9 were predominantly elevated in GM2(+) but not GM2(-) T cells. Similarly, increased staining for GD2 and GD3 but not GD1a was detected with patient T cells with elevated levels of apoptosis in the GD2(+) and GD3(+) cells. These findings suggest that GM2, GD2, and GD3 play a significant role in immune dysfunction observed in RCC patient T cells.

Site-specific anti-tumor immunity: differences in DC function, TGF-beta production and numbers of intratumoral Foxp3+ Treg

Gliomas localized within the CNS are generally not rejected by the immune system despite being immunogenic. This failure of the immune system has been associated both with glioma-derived immunosuppressive molecules and the immune-privileged state of the CNS. However, the relative contribution of tumor location to the glioma-mediated immunosuppression, as well as the immune mechanisms involved in the failure of glioma rejection are not fully defined. We report here that syngeneic GL261 gliomas growing either intracranially or subcutaneously in mice are infiltrated by DC and T cells. However, only subcutaneous gliomas elicit an effective anti-tumor immune response. In contrast to DC infiltrating subcutaneously grown GL261 gliomas, tumor-infiltrating DC from intracranial gliomas do not activate antigen-dependent T-cell proliferation in vitro. In addition, brain-localized GL261 gliomas are characterized by significantly higher numbers of Foxp3(+) Treg and higher levels of TGF-beta1 mRNA and protein expression when compared with GL261 gliomas in the skin. Our data show that gliomas in the CNS, but not in the skin, give rise to TGF-beta production and accumulation of both Treg and functionally impaired DC. Thus, not the tumor itself, but its location dictates the efficiency of the anti-tumor immune response.

Novel antibody-based therapeutic agents targeting CD70: a potential approach for treating Waldenström's macroglobulinemia

Targeting leukocyte differentiation antigens is a validated approach to develop therapeutic agents for the treatment of cancer, autoimmunity, and inflammatory diseases. A subset of activation antigens transiently induced on leukocytes is particularly interesting because many of them are absent from normal tissues, including those of most vital organs, and therapeutic agents' targeting of such antigens is expected to impart limited toxicity. One such antigen, CD70, has recently emerged as an attractive potential drug target for the treatment of cancers. Whereas CD70 is only transiently expressed on activation T and B cells and mature dendritic cells, it is found to be aberrantly expressed on a variety of tumor cells, including Waldenström's macroglobulinemia. In this report, we discuss potential antibody-based therapeutic approaches targeting CD70 for tumor elimination where various mechanisms such as antibody effector functions, immune enhancement, blockade of paracrine growth loop, and delivery of cytotoxic payloads can be exploited to achieve efficacy. Indeed, early clinical trials with therapeutic anti-CD70 antibodies are currently in progress, and those for anti-CD70 drug conjugates will soon follow.

GD3, an overexpressed tumor-derived ganglioside, mediates the apoptosis of activated but not resting T cells

We previously elucidated an important role for gangliosides in renal cell carcinoma-mediated T lymphocyte apoptosis, although the mechanism by which they mediated lymphocyte death remained unclear. Here, we show that when added in purified form, GD3 is internalized by activated T cells, initiating a series of proapoptotic events, including the induction of reactive oxygen species (ROS), an enhancement of p53 and Bax accumulation, an increase in mitochondrial permeability, cytochrome c release, and the activation of caspase-9. GD3-induced apoptosis of activated T cells was dose dependent and inhibitable by pretreating the lymphocytes with N-acetylcysteine, cyclosporin A, or bongkrekic acid, emphasizing the essential role of ROS and mitochondrial permeability to the process. Ganglioside-induced T-cell killing was associated with the caspase-dependent degradation of nuclear factor-kappaB-inducible, antiapoptotic proteins, including RelA; this suggests that their loss is initiated only after the cascade is activated and that their disappearance amplifies but not triggers GD3 susceptibility. Resting T cells did not internalize appreciable levels of GD3 and did not undergo any of the proapoptotic changes that characterize activated T lymphocytes exposed to the ganglioside. RelA overexpression endows Jurkat cells with resistance to GD3-mediated apoptosis, verifying the role of the intact transcription factor in mediating protection from the ganglioside.

Topotecan enhances immune clearance of gliomas

Despite aggressive surgery, radiation therapy, and chemotherapy, glioblastoma multiforme (GBM) is refractory to therapy, recurs quickly, and results in a median survival time of only 14 months. The modulation of the apoptotic receptor Fas with cytotoxic agents could potentiate the response to therapy. However, Fas ligand (FasL) is not expressed in the brain and therefore this Fas-inducing cell death mechanism cannot be utilized. Vaccination of patients with gliomas has shown promising responses. In animal studies, brain tumors of vaccinated mice were infiltrated with activated T cells. Since activated immune cells express FasL, we hypothesized that combination of immunotherapy with chemotherapy can activate Fas signaling, which could be responsible for a synergistic or additive effect of the combination. When we treated the human glioma cell line U-87 and GBM tumor cells isolated from patients with TPT, Fas was up regulated. Subsequent administration of soluble Fas ligand (sFasL) to treated cells significantly increased their cell death indicating that these Fas receptors were functional. Similar effect was observed when CD3(+) T cells were used as a source of the FasL, indicating that the up regulated Fas expression on glioma cells increases their susceptibility to cytotoxic T cell killing. This additive effect was not observed when glioma cells were pre-treated with temozolomide, which was unable to increase Fas expression in tumor. Inhibition of FasL activity with the antagonistic antibody Nok-1 mitigated these effects confirming that these responses were specifically mediated by the Fas-FasL interaction. Furthermore, the CD3(+) T cells co-cultured with topotecan treated U-87 and autologous GBM tumor cells showed a significant increase in expression in IFN-gamma, a key cytokine produced by activated T cells, and accordingly enhanced tumor cytotoxicity. Based on our data we conclude that drugs, such as topotecan, which cause up regulation of Fas on glioma cells can be potentially exploited with immunotherapy to enhance immune clearance of tumors via Fas signaling.

Targeting CD70 for human therapeutic use

Expression of CD70, a member of the tumor necrosis factor superfamily, is restricted to activated T-and B-lymphocytes and mature dendritic cells. Binding of CD70 to its receptor, CD27, is important in priming, effector functions, differentiation and memory formation of T-cells as well as plasma and memory B-cell generation. Antibody blockade of CD70-CD27 interaction inhibits the onset of experimental autoimmune encephalomyelits and cardiac allograft rejection in mice. CD70 has been also detected on hematological tumors and on carcinomas. The highly restricted expression pattern of CD70 in normal tissues and its widespread expression in various malignancies as well as its potential role in autoimmune and inflammatory conditions makes it an attractive target for antibody-based therapeutics. This chapter provides an overview of the physiological role of CD70-CD27 interactions and discusses various approaches to target this pathway for therapeutic use in cancers and autoimmunity.

Immunotherapeutic approaches for glioma

The development of effective immunotherapy strategies for glioma requires adequate understanding of the unique immunological microenvironment in the central nervous system (CNS) and CNS tumors. Although the CNS is often considered to be an immunologically privileged site and poses unique challenges for the delivery of effector cells and molecules, recent advances in technology and discoveries in CNS immunology suggest novel mechanisms that may significantly improve the efficacy of immunotherapy against gliomas. In this review, we first summarize recent advances in the CNS and CNS tumor immunology. We address factors that may promote immune escape of gliomas. We also review advances in passive and active immunotherapy strategies for glioma, with an emphasis on lessons learned from recent early-phase clinical trials. We also discuss novel immunotherapy strategies that have been recently tested in non-CNS tumors and show great potential for application to gliomas. Finally, we discuss how each of these promising strategies can be combined to achieve clinical benefit for patients with gliomas.

CD70 as a therapeutic target in human malignancies

BACKGROUND

Expression of CD70, a member of the tumor necrosis factor superfamily, is restricted to activated T and B lymphocytes and mature dendritic cells. CD70 has also been detected on hematological tumors and on carcinomas. The restricted expression pattern of CD70 in normal tissues and its widespread expression in various malignancies makes it an attractive target for antibody-based therapeutics. Investigations to exploit CD70 as a cancer target have lead to the identification of potential antibody-based clinical candidates. Anti-CD70 antibodies for therapeutic use have been developed and used to validate CD70 as a target for cancers. Antibodies are also used as a vehicle to deliver potent cytotoxic drugs to target CD70+ malignant cells. Both unconjugated antibodies and antibody-drug conjugates targeting CD70 have been tested in animal models of human cancers.

OBJECTIVE

To describe the expression of CD70 in cancer cells and the development of antibody-based therapies against CD70.

METHODS

A review of the available literature.

RESULTS/CONCLUSIONS

Humanized anti-CD70 antibodies have shown significant antitumor activity in preclinical xenograft models of cancer. Additionally, anti-CD70 antibody-drug conjugates exhibit potent antitumor activity in solid tumor xenograft models, confirming increased therapeutic efficacy through cytotoxic drug delivery. Thus, preclinical animal models have provided strong evidence that targeting CD70 either with unconjugated antibodies or with antibody-drug conjugates represents a promising approach to treat human malignancies.

Highly enhanced expression of CD70 on human T-lymphotropic virus type 1-carrying T-cell lines and adult T-cell leukemia cells

Human T-lymphotropic virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia (ATL). In Japan, the number of HTLV-1 carriers is estimated to be 1.2 million and more than 700 cases of ATL have been diagnosed every year. Considering the poor prognosis and lack of curative therapy of ATL, it seems mandatory to establish an effective strategy for the treatment of ATL. In this study, we attempted to identify the cell surface molecules that will become suitable targets of antibodies for anti-ATL therapy. The expression levels of approximately 40,000 host genes of three human T-cell lines carrying HTLV-1 genomes were analyzed by oligonucleotide microarray and compared with the expression levels of the genes in an HTLV-1-negative T-cell line. The HTLV-1-carrying T-cell lines used for experiments had totally different expression patterns of viral genome. Among the genes evaluated, the expression levels of 108 genes were found to be enhanced more than 10-fold in all of the T-cell lines examined and 11 of the 108 genes were considered to generate the proteins expressed on the cell surface. In particular, the CD70 gene was upregulated more than 1,000-fold and the enhanced expression of the CD70 molecule was confirmed by laser flow cytometry for various HTLV-1-carrying T-cell lines and primary CD4(+) T cells isolated from acute-type ATL patients. Such expression was not observed for primary CD4(+) T cells isolated from healthy donors. Since CD70 expression is strictly restricted in normal tissues, such as highly activated T and B cells, CD70 appears to be a potential target for effective antibody therapy against ATL.

Variation in cytotoxic T-lymphocyte responses to peptides derived from tyrosinase-related protein-2

In this study, we developed three optimized peptide ligands (OPL) that demonstrate increased affinities for HLA-A*0201 compared with wild-type tyrosinase-related protein-2 (TRP-2) peptide. The OPL contain amino acids from TRP-2((180-188)) and preferred primary and auxiliary HLA-A*0201 anchor residues. Cytotoxic T lymphocyte (CTL) lines were generated against wild-type TRP-2 peptide and OPL by multiple rounds of peptide stimulation of peripheral blood mononuclear cells from HLA-A2*0201(+) healthy individuals. CTL reactivity profiles to three different OPL were donor-dependent. Among donors, at least one OPL was particularly stimulatory and elicited high levels of CTL that cross-reacted with wild-type TRP-2 peptide. Cytotoxicity assays using CTL raised on wild-type TRP-2 peptide or OPL demonstrated lysis of HLA-A2-positive glioblastoma cells. Molecular models of TRP-2 and OPL peptides docked with HLA-A*0201 demonstrated that substitution of F for S at position 1 (P1) oriented the peptides favoring a pi-pi aromatic interaction with W 167 of HLA-A*0201. This in turn positions P5 and P8 aromatic rings to face solvent that may promote binding to the T-cell receptor, leading to a robust T-cell activation. The results of this study further substantiate the concept that rational design and testing of multiple peptides for the same T-cell epitope should elicit a broader response among different individuals than single peptide immunization. Our results may partially explain why some patients have better clinical responses to peptide-based immunotherapy, whereas others respond poorly.

T-cell death and cancer immune tolerance

Cancer patients mount adaptive immune responses against their tumors. However, tumor develops many mechanisms to evade effective immunosurveillance. T-cell death caused by tumor plays a critical role in establishing tumor immunotolerance. Chronic stimulation of T cells by tumors leads to activation-induced cell death. Abortive stimulation of T cells by tolerogenic antigen-presenting cells loaded with tumor antigens leads to autonomous death of tumor-specific T cells. Therapeutic approaches that prevent T-cell death in the tumor microenvironment and tumor draining lymph nodes, therefore, should boost adaptive immune responses against cancer.

Significance of endogenous augmentation of antiganglioside IgM in cancer patients: potential tool for early detection and management of cancer therapy

Gangliosides expressed by solid malignancies are shed into the circulation at a rate that varies with tumor stage, burden, and progression. Gangliosides have an immunosuppressive effect; thus an increase in the total ganglioside (TG) serum level may coincide with tumor progression. However, circulating gangliosides also may induce an endogenous IgM response. Unlike conventional pentameric IgM antibodies against peptide antigens, antiganglioside IgM antibodies can be polymeric and may not have a J-chain. Because these antibodies can remove shed gangliosides from the tumor microenvironment and the circulation, therapy that actively or passively augments serum levels of IgM against tumor-derived immunosuppressive gangliosides might restore immunocompetence and thereby slow tumor progression. The success of this approach, in passive and active specific therapy of cancer patients, requires analysis of biopsy tissue or sera of therapy recipients to confirm the presence of target gangliosides, such as GM2 or GD3. A patient's response to active or passive immunotherapy against a specific ganglioside target(s) can be monitored by serial assessment of serum specimens for TG level and antiganglioside IgM titer(s). This tailored approach to immunotherapy could be incorporated in postoperative adjuvant protocols.

Immunosuppressive strategies that are mediated by tumor cells

Despite major advances in understanding the mechanisms leading to tumor immunity, a number of obstacles hinder the successful translation of mechanistic insights into effective tumor immunotherapy. Such obstacles include the ability of tumors to foster a tolerant microenvironment and the activation of a plethora of immunosuppressive mechanisms, which may act in concert to counteract effective immune responses. Here we discuss different strategies employed by tumors to thwart immune responses, including tumor-induced impairment of antigen presentation, the activation of negative costimulatory signals, and the elaboration of immunosuppressive factors. In addition, we underscore the influence of regulatory cell populations that may contribute to this immunosuppressive network; these include regulatory T cells, natural killer T cells, and distinct subsets of immature and mature dendritic cells. The current wealth of preclinical information promises a future scenario in which the synchronized blockade of immunosuppressive mechanisms may be effective in combination with other conventional strategies to overcome immunological tolerance and promote tumor regression.

Immune escape for renal cell carcinoma: CD70 mediates apoptosis in lymphocytes

Tumors can escape immune recognition and destruction through the induction of apoptosis in lymphocytes. Although renal cell carcinoma (RCC) is able to prevent immune recognition, only a few genes (such as FasL) that are relevant for RCC immune escape have been identified so far. We have previously shown that some apoptosis-inducing genes are overexpressed in RCC. We hypothesized that these genes could be part of the immune-escape strategy of these tumors. Here we report that CD70, a cytokine overexpressed in RCC, promotes lymphocyte apoptosis through interaction with its receptor CD27 and with the intracellular receptor-binding protein SIVA. Apoptosis increased after cocultivating lymphocytes with the RCC cell lines A498 and CAKI2. The addition of recombinant soluble CD70 to both native lymphocytes and a T-cell cell line resulted in increased lymphocyte apoptosis as well. Furthermore, induced apoptosis could be partially blocked with anti-CD27 and anti-CD70 antibodies. Our results strongly indicate a role for CD70 and CD27 receptor in lymphocyte apoptosis within the tumor environment. Apoptosis mediated by exposure to the CD70 secreted by tumor cells may contribute to the failure of RCC patients to develop an effective lymphocyte-mediated antitumor response.

Memory T cells in human tumor and chronic inflammatory microenvironments: sleeping beauties re-awakened by a cytokine kiss

Human tumors often progress and spread in spite of the presence of large numbers of CD4+ and CD8+ T cells with activated or memory cell phenotypes. The T cells in the microenvironment of human lung tumors fail to be activated in response to stimulation via the T cell receptor and CD28 under conditions that fully activate T cells derived from the peripheral blood of the cancer patients. A combination of regulatory mechanisms which are also observed in a variety of different chronic inflammatory conditions may contribute to the T cell unresponsiveness, and to their inability to respond to and kill tumor cells. The non-responsiveness of memory T cells isolated from human lung tumors and non-malignant chronic inflammatory tissues can be reversed in vitro by a brief pulse with IL-12, and the local and sustained release of exogenous IL-12 into the microenvironment of human tumor xenografts in SCID mice re-activates the tumor-associated T cells in situ. In the later case, the T cells proliferate, secrete interferon-gamma and initiate a cascade of events that culminate in the eradication of tumor cells from the xenograft. In transplantable and spontaneously developing tumors of mice the injection of a single tumor nodule with IL-12 loaded biodegradable microspheres activates tumor-associated T cells to kill tumor cells in situ, and provokes a systemic anti-tumor response that results in the eradication of distant metastatic tumor nodules that are not treated with the cytokine. These mice exhibit a systemic tumor specific immunity as they resist a second challenge with the same (but not a different) tumor. These findings suggest that it will be possible to provoke a systemic anti-tumor immunity in cancer patients by the direct injection of IL-12 loaded biodegradable microspheres or liposomes to locally deliver very low but sustained doses of IL-12 into a single tumor site. This strategy which is based upon the ability of IL-12 to re-activate tumor-associated T cells is termed in situ tumor vaccination.

GM2 expression in renal cell carcinoma: potential role in tumor-induced T-cell dysfunction

Multiple mechanisms have been proposed to account for immune escape by tumors. Although gangliosides have long been known to suppress T-cell immunity, few studies have examined the effect of human tumor-derived gangliosides on immune responses. Here, we show that gangliosides isolated from renal cell carcinoma (RCC) cell lines and clear cell tumor tissue can induce apoptosis in peripheral blood T cells. The RCC tissue-derived gangliosides also suppressed IFN-gamma and, in many cases, interleukin-4 production by CD4+ T cells at concentrations (1 ng/mL-100 pg/mL) well below those that induce any detectable T-cell death (4-20 microg/mL). Additional findings show that GM2 expressed by RCC plays a significant role in promoting T-cell dysfunction. This is supported by the demonstration that all RCC cell lines examined (n = 5) expressed GM2 as did the majority of tumors (15 of 18) derived from patients with clear cell RCC. Furthermore, an antibody specific for GM2 (DMF10.167.4) partially blocked (50-60%) T-cell apoptosis induced by coculturing lymphocytes with RCC cell lines or with RCC tissue-derived gangliosides. DMF10.167.4 also partially blocked the suppression of IFN-gamma production induced by RCC tissue-derived gangliosides, suggesting that GM2 plays a role in down-regulating cytokine production by CD4+ T cells.

T-cell apoptosis in human glioblastoma multiforme: Implications for immunotherapy

We used immunohistochemistry and flow cytometry to assess apoptosis in human glioblastoma multiforme (GBM). Our immunohistochemical study revealed apoptosis of glioma cells expressing glial fibrillary acidic protein and of CD3(+) T cells infiltrating GBM. To quantify and phenotype the apoptotic T cells, we performed flow cytometry on lymphocytes separated from GBM. The cells were stained with annexin-V-FLUOS/propidium iodide to identify apoptosis. We found that high proportions of both the CD4(+) and CD8(+) T cells were apoptotic. In particular, we found that T cells expressing Fas ligand (Fas-L, CD95L) were eight times more vulnerable to apoptosis than those not expressing Fas-L, which suggests that the T-cell apoptosis is induced by overactivation of the T-cell receptor, possibly in the absence of appropriate costimulation. Our results have implications for the design of immunotherapies for GBM.

Lymphocyte activation antigen CD70 expressed by renal cell carcinoma is a potential therapeutic target for anti-CD70 antibody-drug conjugates

Metastatic renal cell carcinoma (RCC) is an aggressive disease refractory to most existing therapeutic modalities. Identifying new markers for disease progression and drug targets for RCC will benefit this unmet medical need. We report a subset of clear cell and papillary cell RCC aberrantly expressing the lymphocyte activation marker CD70, a member of the tumor necrosis factor superfamily. Importantly, CD70 expression was found to be maintained at the metastatic sites of RCC. Anti-CD70 antibody-drug conjugates (ADC) consisting of auristatin phenylalanine phenylenediamine (AFP) or monomethyl auristatin phenylalanine (MMAF), two novel derivatives of the anti-tubulin agent auristatin, mediated potent antigen-dependent cytotoxicity in CD70-expressing RCC cells. Cytotoxic activity of these anti-CD70 ADCs was associated with their internalization and subcellular trafficking through the endosomal-lysosomal pathway, disruption of cellular microtubule network, and G2-M phase cell cycle arrest. The efficiency of drug delivery using anti-CD70 as vehicle was illustrated by the much enhanced cytotoxicity of antibody-conjugated MMAF compared with free MMAF. Hence, ADCs targeted to CD70 can selectively recognize RCC, internalize, and reach the appropriate subcellular compartment(s) for drug release and tumor cell killing. In vitro cytotoxicity of these ADCs was confirmed in xenograft models using RCC cell lines. Our findings provide evidence that CD70 is an attractive target for antibody-based therapeutics against metastatic RCC and suggest that anti-CD70 ADCs can provide a new treatment approach for advanced RCC patients who currently have no chemotherapeutic options.

Immune stimulatory effects of CD70 override CD70-mediated immune cell apoptosis in rodent glioma models and confer long-lasting antiglioma immunityin vivo

CD70 (CD27 ligand) promotes the expansion of primed lymphocytes by enhancing cell survival. Surprisingly, we previously observed that CD70 aberrantly expressed on human glioma cells promoted immune cell apoptosis and inhibited alloreactive lysis. Here we report that ectopic expression of CD70 in mouse glioma cells enhances apoptosis of T, B and NK cells in coculture, but nevertheless promotes glioma cell lysis by NK cells in vitro. In nude mice, CD70 expression in SMA-560 gliomas delays the glioma growth upon subcutaneous (s.c.) or intracerebral (i.c.) inoculation, suggesting a role for CD70/CD27-dependent NK cell activity in tumor surveillance. In syngeneic immunocompetent VM/Dk mice, CD70 allows the rejection of s.c. and i.c. implanted SMA-560 tumors. The tumorigenicity of CD70-expressing glioma cells is abrogated when TGF-beta signaling is blocked. Moreover, mice surviving the s.c. CD70 glioma challenge subsequently also reject wild-type glioma cells administered i.c. Similarly, CD70-expressing GL-261 gliomas are rejected in syngeneic C57BL/6 mice, while glioma growth is restored in C57BL/6 CD27(-/-) mice, suggesting that the CD70/CD27 interaction recruits a tumor-specific T-cell repertoire and induces tumor-specific memory. Altogether, these observations indicate that the net effect of aberrant CD70 expression in gliomas is immune stimulatory rather than immune paralytic and encourage its application in tumor immunotherapy.

Endogenous GD3 ganglioside induces apoptosis in U-1242 MG glioma cells

GD3 ganglioside induces apoptosis in several cell types, but the molecular events through which this occurs are largely unknown. We investigated the apoptotic effects of GD3 expression using U-1242 MG glioblastoma cells, as these cells synthesize almost exclusively GM3 and GM2 but not GD3. To express GD3 under the control of the TetOn system with minimum leakage, we modified the system by constructing a single tri-cistronic retrovirus vector containing three genes separated by two internal ribosome entry sites: (a) transcriptional silencer, tTS; (b) mutant of reverse transcriptional activator, rtTA2(S)-M2 (provided by H. Bujard, Heidelberg, Germany); and (c) enhanced green fluorescent protein (EGFP), as an indicator of the tri-cistronic gene expression. Using flow cytometry, we selected glioma cells (U1242MG-GD3 clone) that express high levels of GD3 in response to doxycycline. Expression of GD3 was associated with apoptosis as verified by annexin-V binding, TdT-mediated dUTPnick end-labelling assay (TUNEL), and EGFP degradation. GD3-induced apoptosis occurred via caspase-8 activation, as GD3 caused cleavage of caspase-8 and inhibition of caspase-8 activation by zlETD-fmk minimized GD3-induced apoptosis.