CD70/CD27 ligand, a member of the TNF family, is expressed in human brain tumors

The development of chimeric antigen receptor T-cells against CD70 for renal cell carcinoma treatment

In this study, we investigated CD70 as a promising target for renal cell carcinoma (RCC) therapy and developed a potent chimeric antigen receptor T (CAR-T) cells for potential clinical testing. CD70, found to be highly expressed in RCC tumors, was associated with decreased survival. We generated CAR-T cells expressing VHH sequence of various novel nanobodies from immunized alpaca and a single-chain variable fragment (scFv) derived from human antibody (41D12). In our in vitro experiments, anti-CD70 CAR-T cells effectively eliminated CD70-positive tumor cells while sparing CD70-negative cells. The nanobody-based CAR-T cells demonstrated significantly higher production of cytokines such as IL-2, IFN-γ and TNF-ɑ during co-culture, indicating their potential for enhanced functionality. In xenograft mouse model, these CAR-T cells exhibited remarkable anti-tumor activity, leading to the eradication of RCC tumor cells. Importantly, human T cell expansion after infusion was significantly higher in the VHH groups compared to the scFv CAR-T group. Upon re-challenging mice with RCC tumor cells, the VHH CAR-T treated group remained tumor-free, suggesting a robust and long-lasting anti-tumor response. These findings provide strong support for the potential of nanobody-based CD70 CAR-T cells as a promising therapeutic option for RCC. This warrants further development and consideration for future clinical trials and applications.

The novel high-affinity humanized antibody IMM40H targets CD70, eliminates tumors via Fc-mediated effector functions, and interrupts CD70/CD27 signaling

Background

A significant level of CD70 can be detected in various types of tumor tissues and CD27 is expressed on Treg cells, but CD70 expression is low in normal tissues. The interaction between CD70 and CD27 can stimulate the proliferation and survival of cancer cells and increase the level of soluble CD27, which is associated with poor prognosis in patients with lymphoma and certain solid tumors. Thus, it is a promising therapeutic target for the treatment of many major CD70+ cancer indications, including CD70+ lymphoma, RCC, NSCLC, HNSCC and OC.

Methods

IMM40H was obtained through hybridoma screening and antibody humanization techniques. IMM40H was evaluated for its binding, blocking, Fc-dependent effector functions and antitumor activity characteristics in various in vitro and in vivo systems. The safety and tolerability profile of IMM40H were evaluated through single and repeated administration in cynomolgus monkeys.

Results

In vitro cell-based assays demonstrated that IMM40H had considerably stronger CD70-binding affinity than competitor anti-CD70 antibodies, including cusatuzumab, which enabled it to block the interaction of between CD70 and CD27 more effectively. IMM40H also exhibited potent Fc-dependent effector functions (ADCC/CDC/ADCP), and could make a strong immune attack on tumor cells and enhance therapeutic efficacy. Preclinical findings showed that IMM40H had potent antitumor activity in multiple myeloma U266B1 xenograft model, and could eradicate subcutaneously established tumors at a low dose of 0.3 mg/kg. IMM40H (0.3 mg/kg) showed therapeutic effects faster than cusatuzumab (1 mg/kg). A strong synergistic effect between IMM01 (SIRPα-Fc fusion protein) and IMM40H was recorded in Burkitt's lymphoma Raji and renal carcinoma cell A498 tumor models. In cynomolgus monkeys, the highest non-severely toxic dose (HNSTD) for repeat-dose toxicity was up to 30 mg/kg, while the maximum tolerated dose (MTD) for single-dose toxicity was up to 100 mg/kg, confirming that IMM40H had a good safety and tolerability profile.

Conclusion

IMM40H is a high-affinity humanized IgG1 specifically targeting the CD70 monoclonal antibody with enhanced Fc-dependent activities. IMM40H has a dual mechanism of action: inducing cytotoxicity against CD70+ tumor cells via various effector functions (ADCC, ADCP and CDC) and obstructs the proliferation and activation of Tregs by inhibiting CD70/CD27 signaling.

Overview of CD70 as a Potential Therapeutic Target for Osteosarcoma

Osteosarcoma is a primary malignant bone tumor. Effective chemotherapy regimens for refractory disease are scarce, accounting for no improvement in survival. Immune-based cell therapies have emerged as novel alternatives. However, advancements with these therapies have been seen mostly when immune cells are armed to target specific tumor Ags. Recent studies identified cluster of differentiation 70 (CD70) as a promising target to osteosarcoma particularly because CD70 is highly expressed in osteosarcoma lung metastases (Pahl et al. 2015. Cancer Cell Int. 15: 31), and its overexpression by tumors has been correlated with immune evasion and tumor proliferation (Yang et al. 2007. Blood 110: 2537-2544). However, the limited knowledge of the overall CD70 expression within normal tissues and the potential for off-target effect pose several challenges (Flieswasser et al. 2022. J. Exp. Clin. Cancer Res. 41: 12). Nonetheless, CD70-based clinical trials are currently ongoing and are preliminarily showing promising results for patients with osteosarcoma. The present review sheds light on the recent literature on CD70 as it relates to osteosarcoma and highlights the benefits and challenges of targeting this pathway.

Gene Targets of CAR-T Cell Therapy for Glioblastoma

Glioblastoma (GBM) is an aggressive primary brain tumor with a poor prognosis following conventional therapeutic interventions. Moreover, the blood-brain barrier (BBB) severely impedes the permeation of chemotherapy drugs, thereby reducing their efficacy. Consequently, it is essential to develop novel GBM treatment methods. A novel kind of pericyte immunotherapy known as chimeric antigen receptor T (CAR-T) cell treatment uses CAR-T cells to target and destroy tumor cells without the aid of the antigen with great specificity and in a manner that is not major histocompatibility complex (MHC)-restricted. It has emerged as one of the most promising therapy techniques with positive clinical outcomes in hematological cancers, particularly leukemia. Due to its efficacy in hematologic cancers, CAR-T cell therapy could potentially treat solid tumors, including GBM. On the other hand, CAR-T cell treatment has not been as therapeutically effective in treating GBM as it has in treating other hematologic malignancies. CAR-T cell treatments for GBM have several challenges. This paper reviewed the use of CAR-T cell therapy in hematologic tumors and the selection of targets, difficulties, and challenges in GBM.

Tumor Microenvironment in Glioma Invasion

A major malignant trait of gliomas is their remarkable infiltration capacity. When glioma develops, the tumor cells have already reached the distant part. Therefore, complete removal of the glioma is impossible. Recently, research on the involvement of the tumor microenvironment in glioma invasion has advanced. Local hypoxia triggers cell migration as an environmental factor. The transcription factor hypoxia-inducible factor (HIF) -1α, produced in tumor cells under hypoxia, promotes the transcription of various invasion related molecules. The extracellular matrix surrounding tumors is degraded by proteases secreted by tumor cells and simultaneously replaced by an extracellular matrix that promotes infiltration. Astrocytes and microglia become tumor-associated astrocytes and glioma-associated macrophages/microglia, respectively, in relation to tumor cells. These cells also promote glioma invasion. Interactions between glioma cells actively promote infiltration of each other. Surgery, chemotherapy, and radiation therapy transform the microenvironment, allowing glioma cells to invade. These findings indicate that the tumor microenvironment may be a target for glioma invasion. On the other hand, because the living body actively promotes tumor infiltration in response to the tumor, it is necessary to reconsider whether the invasion itself is friend or foe to the brain.

Natural killer cell-related gene signature predicts malignancy of glioma and the survival of patients

Background

Natural killer (NK) cells-based therapies are one of the most promising strategies against cancer. The aim of this study is to investigate the natural killer cell related genes and its prognostic value in glioma.

Methods

The Chinese Glioma Genome Atlas (CGGA) was used to develop the natural killer cell-related signature. Risk score was built by multivariate Cox proportional hazards model. A cohort of 326 glioma samples with whole transcriptome expression data from the CGGA database was included for discovery. The Cancer Genome Atlas (TCGA) datasets was used for validation. GO and KEGG were used to reveal the biological process and function associated with the natural killer cell-related signature. We also collected the clinical pathological features of patients with gliomas to analyze the association with tumor malignancy and patients’ survival.

Results

We screened for NK-related genes to build a prognostic signature, and identified the risk score based on the signature. We found that NK-related risk score was independent of various clinical factors. Nature-killer cell gene expression is correlated with clinicopathological features of gliomas. Innovatively, we demonstrated the tight relation between the risk score and immune checkpoints, and found NK-related risk score combined with PD1/PDL1 patients could predict the patient outcome.

Conclusion

Natural killer cell-related gene signature can predict malignancy of glioma and the survival of patients, these results might provide new view for the research of glioma malignancy and individual immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09230-y.

Glioma targeted therapy: insight into future of molecular approaches

Gliomas are the common type of brain tumors originating from glial cells. Epidemiologically, gliomas occur among all ages, more often seen in adults, which males are more susceptible than females. According to the fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS5), standard of care and prognosis of gliomas can be dramatically different. Generally, circumscribed gliomas are usually benign and recommended to early complete resection, with chemotherapy if necessary. Diffuse gliomas and other high-grade gliomas according to their molecule subtype are slightly intractable, with necessity of chemotherapy. However, for glioblastoma, feasible resection followed by radiotherapy plus temozolomide chemotherapy define the current standard of care. Here, we discuss novel feasible or potential targets for treatment of gliomas, especially IDH-wild type glioblastoma. Classic targets such as the p53 and retinoblastoma (RB) pathway and epidermal growth factor receptor (EGFR) gene alteration have met failure due to complex regulatory network. There is ever-increasing interest in immunotherapy (immune checkpoint molecule, tumor associated macrophage, dendritic cell vaccine, CAR-T), tumor microenvironment, and combination of several efficacious methods. With many targeted therapy options emerging, biomarkers guiding the prescription of a particular targeted therapy are also attractive. More pre-clinical and clinical trials are urgently needed to explore and evaluate the feasibility of targeted therapy with the corresponding biomarkers for effective personalized treatment options.

CD70 as an actionable immunotherapeutic target in recurrent glioblastoma and its microenvironment

PURPOSE

Glioblastoma (GBM) patients suffer from a dismal prognosis, with standard of care therapy inevitably leading to therapy-resistant recurrent tumors. The presence of cancer stem cells (CSCs) drives the extensive heterogeneity seen in GBM, prompting the need for novel therapies specifically targeting this subset of tumor-driving cells. Here, we identify CD70 as a potential therapeutic target for recurrent GBM CSCs.

EXPERIMENTAL DESIGN

In the current study, we identified the relevance and functional influence of CD70 on primary and recurrent GBM cells, and further define its function using established stem cell assays. We use CD70 knockdown studies, subsequent RNAseq pathway analysis, and in vivo xenotransplantation to validate CD70's role in GBM. Next, we developed and tested an anti-CD70 chimeric antigen receptor (CAR)-T therapy, which we validated in vitro and in vivo using our established preclinical model of human GBM. Lastly, we explored the importance of CD70 in the tumor immune microenvironment (TIME) by assessing the presence of its receptor, CD27, in immune infiltrates derived from freshly resected GBM tumor samples.

RESULTS

CD70 expression is elevated in recurrent GBM and CD70 knockdown reduces tumorigenicity in vitro and in vivo. CD70 CAR-T therapy significantly improves prognosis in vivo. We also found CD27 to be present on the cell surface of multiple relevant GBM TIME cell populations, notably putative M1 macrophages and CD4 T cells.

CONCLUSION

CD70 plays a key role in recurrent GBM cell aggressiveness and maintenance. Immunotherapeutic targeting of CD70 significantly improves survival in animal models and the CD70/CD27 axis may be a viable polytherapeutic avenue to co-target both GBM and its TIME.

A Disintegrin and Metalloproteinase (ADAM) Family: Their Significance in Malignant Tumors of the Central Nervous System (CNS)

Despite the considerable advances in diagnostic methods in medicine, central nervous system (CNS) tumors, particularly the most common ones-gliomas-remain incurable, with similar incidence rates and mortality. A growing body of literature has revealed that degradation of the extracellular matrix by matrix metalloproteinases (MMPs) might be involved in the pathogenesis of CNS tumors. However, the subfamily of MMPs, known as disintegrin and metalloproteinase (ADAM) proteins are unique due to both adhesive and proteolytic activities. The objective of our review is to present the role of ADAMs in CNS tumors, particularly their involvement in the development of malignant gliomas. Moreover, we focus on the diagnostic and prognostic significance of selected ADAMs in patients with these neoplasms. It has been proven that ADAM12, ADAMTS4 and 5 are implicated in the proliferation and invasion of glioma cells. In addition, ADAM8 and ADAM19 are correlated with the invasive activity of glioma cells and unfavorable survival, while ADAM9, -10 and -17 are associated with tumor grade and histological type of gliomas and can be used as prognostic factors. In conclusion, several ADAMs might serve as potential diagnostic and prognostic biomarkers as well as therapeutic targets for malignant CNS tumors. However, future research on ADAMs biology should be performed to elucidate new strategies for tumor diagnosis and treatment of patients with these malignancies.

T lymphocyte-targeted immune checkpoint modulation in glioma

Immunomodulatory therapies targeting inhibitory checkpoint molecules have revolutionized the treatment of solid tumor malignancies. Concerns about whether systemic administration of an immune checkpoint inhibitor could impact primary brain tumors were answered with the observation of definitive responses in pediatric patients harboring hypermutated gliomas. Although initial clinical results in patients with glioblastoma (GBM) were disappointing, recently published results have demonstrated a potential survival benefit in patients with recurrent GBM treated with neoadjuvant programmed cell death protein 1 blockade. While these findings necessitate verification in subsequent studies, they support the possibility of achieving clinical meaningful immune responses in malignant primary brain tumors including GBM, a disease in dire need of additional therapeutic options. There are several challenges involved in treating glioma with immune checkpoint modulators including the immunosuppressive nature of GBM itself with high inhibitory checkpoint expression, the immunoselective blood brain barrier impairing the ability for peripheral lymphocytes to traffic to the tumor microenvironment and the high prevalence of corticosteroid use which suppress lymphocyte activation. However, by simultaneously targeting multiple costimulatory and inhibitory pathways, it may be possible to achieve an effective antitumoral immune response. To this end, there are now several novel agents targeting more recently uncovered “second generation” checkpoint molecules. Given the multiplicity of drugs being considered for combination regimens, an increased understanding of the mechanisms of action and resistance combined with more robust preclinical and early clinical testing will be needed to be able to adequately test these agents. This review summarizes our current understanding of T lymphocyte-modulating checkpoint molecules as it pertains to glioma with the hope for a renewed focus on the most promising therapeutic strategies.

Innovative and Promising Strategies to Enhance Effectiveness of Immunotherapy for CNS Tumors: Where Are We?

Although there are several immunotherapy approaches for the treatment of Central Nervous System (CNS) tumors under evaluation, currently none of these approaches have received approval from the regulatory agencies. CNS tumors, especially glioblastomas, are tumors characterized by highly immunosuppressive tumor microenvironment, limiting the possibility of effectively eliciting an immune response. Moreover, the peculiar anatomic location of these tumors poses relevant challenges in terms of safety, since uncontrolled hyper inflammation could lead to cerebral edema and cranial hypertension. The most promising strategies of immunotherapy in neuro-oncology consist of the use of autologous T cells redirected against tumor cells through chimeric antigen receptor (CAR) constructs or genetically modified T-cell receptors. Trials based on native or genetically engineered oncolytic viruses and on vaccination with tumor-associated antigen peptides are also under evaluation. Despite some sporadic complete remissions achieved in clinical trials, the outcome of patients with CNS tumors treated with different immunotherapeutic approaches remains poor. Based on the lessons learned from these unsatisfactory experiences, novel immune-therapy approaches aimed at overcoming the profound immunosuppressive microenvironment of these diseases are bringing new hope to reach the cure for CNS tumors.

CD70 expression determines the therapeutic efficacy of expanded human regulatory T cells

Regulatory T cells (Tregs) are critical mediators of immune homeostasis. The co-stimulatory molecule CD27 is a marker of highly suppressive Tregs, although the role of the CD27-CD70 receptor-ligand interaction in Tregs is not clear. Here we show that after prolonged in vitro stimulation, a significant proportion of human Tregs gain stable CD70 expression while losing CD27. The expression of CD70 in expanded Tregs is associated with a profound loss of regulatory function and an unusual ability to provide CD70-directed co-stimulation to TCR-activated conventional T cells. Genetic deletion of CD70 or its blockade prevents Tregs from delivering this co-stimulatory signal, thus maintaining their regulatory activity. High resolution targeted single-cell RNA sequencing of human peripheral blood confirms the presence of CD27-CD70+ Treg cells. These findings have important implications for Treg-based clinical studies where cells are expanded over extended periods in order to achieve sufficient treatment doses.

Tandem CAR-T cells targeting CD70 and B7-H3 exhibit potent preclinical activity against multiple solid tumors

Purpose: Given that heterogeneous expression and variants of antigens on solid tumors are responsible for relapse after chimeric antigen receptor (CAR)-T cell therapy, we hypothesized that combinatorial targeting two tumor-associated antigens would lessen this problem and enhance the antitumor activity of T cells.

Methods: The co-expression level of CD70 and B7-H3 was analyzed in multiple tumor tissue samples. Further, two putative antigens were identified in The Cancer Genome Atlas and Gene Expression Profiling Interactive Analysis database. Two CD70 targeted CARs with different antigen binding domain, truncated CD27 and CD70 specific single-chain antibody fragment (scFv), were designed to screen a more suitable target-antigen binding moiety. Accordingly, we designed a bivalent tandem CAR (TanCAR) and further assessed the anti-tumor efficacy of TanCAR-T cells in vitro and in vivo.

Results: Our results indicated that co-expression of CD70 and B7-H3 was observed on multiple tumor types including kidney, breast, esophageal, liver, colon cancer, glioma as well as melanoma. The CD70 targeted CAR-T cells with binding moiety of CD70 specific scFv exhibit a higher affinity and antitumor effect against CD70⁺ tumor cells. TanCAR-T cells induced enhanced ability of cytolysis and cytokine release over unispecific CAR-T cells when encountering tumor cells expressing two target-antigens. Further, low doses of TanCAR-T cells could also effectively control the lung cancer and melanoma xenografts and improved overall survival of the treated animals.

Conclusion: TanCAR-T cells targeting CD70 and B7-H3 exhibit enhanced antitumor functionality and improve the problem of antigenic heterogeneity and variant in the treatment against solid tumor and melanoma.

The prognostic role of NK cells and their ligands in squamous cell carcinoma of the head and neck: a systematic review and meta-analysis

Background : Despite the improvement in therapeutic interventions, 5-year survival rates in Head and Neck Squamous Cell Carcinoma (HNSCC) are limited. HNSCC is an immunogenic cancer type for which molecular stratification markers are lacking. Tumor-infiltrating lymphocytes (TILs) have shown a favorable prognostic role in different cancer types. This study focused on the prognostic role of NK cells in HNSCC. Methods : A systematic search was conducted in Pubmed/Medline and Embase. Articles that correlated the presence of intratumoral NK cells, activating/inhibiting receptors, death receptors, or their ligands with clinicopathologic characteristics or survival were included. A meta-analysis was performed that assessed the association between CD56+ and CD57+ and overall survival (OS), disease-free survival (DFS), and progression-free survival (PFS). Results : A pooled analysis indicated a favorable prognostic role of CD56+ and CD57+ NK cells for OS (HR 0.19 CI 0.11-0.35). NK cell markers NKp46 and Granzyme B (GrB) also have a favorable prognostic role. NK cell ligand Fas correlated with better survival and better characteristics. NK cell marker Fas-L, NK cell ligands CEACAM1, RCAS1, CD70 and TRAIL-R, and effector molecules of these ligands, FADD and FAP1, correlated to features of worse prognosis. Conclusion : A favorable prognostic role of NK cells in HNSCC was found in this review. Some studies implied the opposite, indicating the fine balance between pro- and anti-tumor functions of NK cells. Future studies using homogeneous patient cohorts regarding tumor subsite and treatment modality, are necessary to further provide insight into the prognostic role of NK cells.

Induction of NKG2D ligand expression on tumor cells by CD8+ T-cell engagement-mediated activation of nuclear factor-kappa B and p300/CBP-associated factor

The ligands for the natural killer group 2 (NKG2D) protein render tumor cells susceptible to NKG2D-dependent immune cell attack. However, cancer cells escape from immune surveillance by downregulating NKG2D ligands. We previously discovered that engagement of activated CD8+ T cells and tumor cells induces NKG2D ligands on tumor cells, but the underlying mechanism remains to be defined. Both in vivo mouse tumor models and in vitro cell assays were performed to study the downstream signaling. Our results supported the notion that, upon engagement with the cognate receptors, CD137 ligand and CD40 initiates activation of nuclear factor-kappa B (NF-κB) signaling in tumor cells even in the absence of CD8+ T cells. Like tumor and CD8+ T cell contact-dependent NKG2D ligand induction, this CD137L/CD40-mediated signaling activation was associated with elevated levels of acetyltransferase P300/CBP-associated factor (PCAF), whereas inhibition of phosphorylated NF-κB abrogated PCAF induction. Although stimulation of CD137L/CD40-mediated signaling is vital, inflammatory cytokines, including interferon gamma (IFNγ) and TNFα, also facilitate NKG2D ligand-induced immune surveillance via both facilitating T-cell chemotaxis and CD137L/CD40 induced NF-κB/PCAF activation. Collectively, our results unveil a novel mechanism of NKG2D ligand upregulation involving reverse signaling of CD40 and CD137L on tumor cells which, along with inflammatory cytokines IFNγ and TNFα, stimulate downstream NF-κB and PCAF activation. Understanding this mechanism may help in development of induced NKG2D ligand-dependent T-cell therapy against cancers.

CAR-Engineered NK Cells for the Treatment of Glioblastoma: Turning Innate Effectors Into Precision Tools for Cancer Immunotherapy

Glioblastoma (GB) is the most common and aggressive primary brain tumor in adults and currently incurable. Despite multimodal treatment regimens, median survival in unselected patient cohorts is <1 year, and recurrence remains almost inevitable. Escape from immune surveillance is thought to contribute to the development and progression of GB. While GB tumors are frequently infiltrated by natural killer (NK) cells, these are actively suppressed by the GB cells and the GB tumor microenvironment. Nevertheless, ex vivo activation with cytokines can restore cytolytic activity of NK cells against GB, indicating that NK cells have potential for adoptive immunotherapy of GB if potent cytotoxicity can be maintained in vivo. NK cells contribute to cancer immune surveillance not only by their direct natural cytotoxicity which is triggered rapidly upon stimulation through germline-encoded cell surface receptors, but also by modulating T-cell mediated antitumor immune responses through maintaining the quality of dendritic cells and enhancing the presentation of tumor antigens. Furthermore, similar to T cells, specific recognition and elimination of cancer cells by NK cells can be markedly enhanced through expression of chimeric antigen receptors (CARs), which provides an opportunity to generate NK-cell therapeutics of defined specificity for cancer immunotherapy. Here, we discuss effects of the GB tumor microenvironment on NK-cell functionality, summarize early treatment attempts with ex vivo activated NK cells, and describe relevant CAR target antigens validated with CAR-T cells. We then outline preclinical approaches that employ CAR-NK cells for GB immunotherapy, and give an overview on the ongoing clinical development of ErbB2 (HER2)-specific CAR-NK cells currently applied in a phase I clinical trial in glioblastoma patients.

CD70, a novel target of CAR T-cell therapy for gliomas

Background

Cancer immunotherapy represents a promising treatment approach for malignant gliomas but is hampered by the limited number of ubiquitously expressed tumor antigens and the profoundly immunosuppressive tumor microenvironment. We identified cluster of differentiation (CD)70 as a novel immunosuppressive ligand and glioma target.

Methods

Normal tissues derived from 52 different organs and primary and recurrent low-grade gliomas (LGGs) and glioblastomas (GBMs) were thoroughly evaluated for CD70 gene and protein expression. The association between CD70 and patients' overall survival and its impact on T-cell death was also evaluated. Human and mouse CD70-specific chimeric antigen receptors (CARs) were tested respectively against human primary GBMs and murine glioma lines. The antitumor efficacies of these CARs were also examined in orthotopic xenograft and syngeneic models.

Results

CD70 was not detected in peripheral and brain normal tissues but was constitutively overexpressed by isocitrate dehydrogenase (IDH) wild-type primary LGGs and GBMs in the mesenchymal subgroup and recurrent tumors. CD70 was also associated with poor survival in these subgroups, which may link to its direct involvement in glioma chemokine productions and selective induction of CD8+ T-cell death. To explore the potential for therapeutic targeting of this newly identified immunosuppressive axis in GBM tumors, we demonstrate that both human and mouse CD70-specific CAR T cells recognize primary CD70+ GBM tumors in vitro and mediate the regression of established GBM in xenograft and syngeneic models without illicit effect.

Conclusion

These studies identify a previously uncharacterized and ubiquitously expressed immunosuppressive ligand CD70 in GBMs that also holds potential for serving as a novel CAR target for cancer immunotherapy in gliomas.

CAR T-cell therapy for glioblastoma: ready for the next round of clinical testing?

INTRODUCTION

The outcome for patients with glioblastoma (GBM) remains poor, and there is an urgent need to develop novel therapeutic approaches. T cells genetically modified with chimeric antigen receptors (CARs) hold the promise to improve outcomes since they recognize and kill cells through different mechanisms than conventional therapeutics. Areas covered: This article reviews CAR design, tumor associated antigens expressed by GBMs that can be targeted with CAR T cells, preclinical and clinical studies conducted with CAR T cells, and genetic approaches to enhance their effector function. Expert commentary: While preclinical studies have highlighted the potent anti-GBM activity of CAR T cells, the initial foray of CAR T-cell therapies into the clinic resulted only in limited benefits for GBM patients. Additional genetic modification of CAR T cells has resulted in a significant increase in their anti-GBM activity in preclinical models. We are optimistic that clinical testing of these enhanced CAR T cells will be safe and result in improved anti-glioma activity in GBM patients.

Expression of CD70 (CD27L) Is Associated With Epithelioid and Sarcomatous Features in IDH-Wild-Type Glioblastoma

Glioblastoma is an aggressive, often recalcitrant disease. In the majority of cases, prognosis is dismal and current therapies only moderately prolong survival. Immunotherapy is increasingly being recognized as an effective treatment modality. CD70 is a transmembrane protein that shows restricted expression in tissue but has been described in various malignancies. Therapeutic targeting of CD70 has demonstrated antitumor efficacy and is in clinical trials. Here, we sought to characterize CD70 expression in a large cohort of gliomas (n = 205) using tissue microarrays. We identified a subset of tumors (n = 18, 8.8% of high-grade gliomas) exhibiting moderate-to-strong immunoreactivity that enriched for the IDH-wild-type glioblastoma variants gliosarcoma (n = 10) and the newly described epithelioid glioblastoma (n = 4). CD70 expression was associated with prolonged survival in gliosarcoma. Analysis of TCGA datasets showed significantly increased CD70 expression in mesenchymal tumors and prolonged survival in recurrent non-G-CIMP high-expressing tumors. In CD70+ gliomas, there was a significant increase in CD68/CD163/HLA-DR+ tumor-associated macrophages, but not CD27+ TIL. These results confirm prior in vitro studies and demonstrate expression in a clinical cohort. The absence of CD70 expression in the post-treatment setting may portend more clinically aggressive disease in gliosarcoma. However, larger-scale studies will be needed to characterize and validate this relationship.

CD70 reverse signaling enhances NK cell function and immunosurveillance in CD27-expressing B-cell malignancies

CD27 expression on malignant B cells triggers CD70 reverse signaling in NK cells and improves lymphoma immunosurveillance. CD70 reverse signaling in NK cells is mediated via the AKT signaling pathway and enhances survival and effector function.

The role of CD27 in anti-viral T-cell immunity

CD27 is a co-stimulatory immune-checkpoint receptor, constitutively expressed on a broad range of T-cells (αβ and γδ), NK-cells and B-cells. Ligation of CD27 with CD70 results in potent co-stimulatory effects. In mice, co-stimulation of CD8⁺ T-cells through CD27 promotes immune activation and enhances primary, secondary, memory and recall responses towards viral infections. Limited in vitro human studies support mouse experiments and show that CD27 co-stimulation enhances antiviral T-cell immunity. Given the potent co-stimulatory effects of CD27, manipulating CD27 signalling is of interest for viral, autoimmune and anti-tumour immunotherapies. This review focuses on the role of CD27 co-stimulation in anti-viral T-cell immunity and discusses clinical studies utilising the CD27 co-stimulation pathway for anti-viral, anti-tumour and autoimmune immunotherapy.

Deficiency of the protein-tyrosine phosphatase DEP-1/PTPRJ promotes matrix metalloproteinase-9 expression in meningioma cells

Brain-invasive growth of a subset of meningiomas is associated with less favorable prognosis. The molecular mechanisms causing invasiveness are only partially understood, however, the expression of matrix metalloproteinases (MMPs) has been identified as a contributing factor. We have previously found that loss of density enhanced phosphatase-1 (DEP-1, also designated PTPRJ), a transmembrane protein-tyrosine phosphatase, promotes meningioma cell motility and invasive growth in an orthotopic xenotransplantation model. We have now analyzed potential alterations of the expression of genes involved in motility control, caused by DEP-1 loss in meningioma cell lines. DEP-1 depleted cells exhibited increased expression of mRNA encoding MMP-9, and the growth factors EGF and FGF-2. The increase of MMP-9 expression in DEP-1 depleted cells was also readily detectable at the protein level by zymography. MMP-9 upregulation was sensitive to chemical inhibitors of growth factor signal transduction. Conversely, MMP-9 mRNA levels could be stimulated with growth factors (e.g. EGF) and inflammatory cytokines (e.g. TNFα). Increase of MMP-9 expression by DEP-1 depletion, or growth factor/cytokine stimulation qualitatively correlated with increased invasiveness in vitro scored as transmigration through matrigel-coated membranes. The studies suggest induction of MMP-9 expression promoted by DEP-1 deficiency, or potentially by growth factors and inflammatory cytokines, as a mechanism contributing to meningioma brain invasiveness.

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.

The neural adhesion molecule L1CAM confers chemoresistance in human glioblastomas

Glioblastoma multiforme (GBM) represents the most common and malignant brain tumor. GBM tissues exhibit elevated expression of the transforming growth factor-beta1 (TGF-β1) and the adhesion molecule L1CAM. This study investigated the mechanism of L1CAM regulation in GBM cells and its role in the mediation of chemoresistance. L1CAM expression levels varied in GBM cells being highest in A172 cells and low in T98G cells. Inhibition of TGF-β1 signaling in A172 cells reduced L1CAM expression and vice versa stimulation with exogenous TGF-β1 led to upregulation of L1CAM in T98G cells. Additionally, TGF-β1 and L1CAM expression increased during differentiation of glioma stem-like cells. L1CAM expressing GBM cells and differentiated glioma stem-like cells showed a reduced apoptotic response after treatment with the chemotherapeutic drug temozolomide. Accordingly, siRNA-mediated knock-down of L1CAM in A172 cells and differentiated glioma stem-like cells increased chemosensitivity, whereas overexpression of L1CAM in T98G cells and glioma spheroids diminished the apoptotic response. Elevated L1CAM expression caused a diminished expression of caspase-8 in GBM and differentiated glioma stem-like cells. These data show that TGF-β1 dependent upregulation of L1CAM expression in GBM cells leads to the downregulation of caspase-8 and apoptosis resistance pointing to L1CAM as potential target for improved therapy of GBM patients.

Antigen-receptor gene-modified T cells for treatment of glioma

Immunological effector cells and molecules have been shown to access intracranial tumor sites despite the existence of blood brain barrier (BBB) or immunosuppressive mechanisms associated with brain tumors. Recent progress in T-cell biology and tumor immunology made possible to develop strategies of tumor-associated antigen-specific immunotherapeutic approaches such as vaccination with defined antigens and adoptive T-cell therapy with antigen-specific T cells including gene-modified T cells for the treatment of patients with brain tumors. An array of recent reports on the trials of active and passive immunotherapy for patients with brain tumors have documented safety and some preliminary clinical efficacy, although the ultimate judgment for clinical benefits awaits rigorous evaluation in trials of later phases. Nevertheless, treatment with lymphocytes that are engineered to express tumor-specific receptor genes is a promising immunotherapy against glioma, based on the significant efficacy reported in the trials for patients with other types of malignancy. Overcoming the relative difficulty to apply immunotherapeutic approach to intracranial region, current advances in the understanding of human tumor immunology and the gene-therapy methodology will address the development of effective immunotherapy of brain tumors.

The role of tumor necrosis factor receptor superfamily members in mammalian brain development, function and homeostasis

Tumor necrosis factor receptor superfamily (TNFRSF) members were initially identified as immunological mediators, and are still commonly perceived as immunological molecules. However, our understanding of the diversity of TNFRSF members' roles in mammalian physiology has grown significantly since the first discovery of TNFRp55 (TNFRSF1) in 1975. In particular, the last decade has provided evidence for important roles in brain development, function and the emergent field of neuronal homeostasis. Recent evidence suggests that TNFRSF members are expressed in an overlapping regulated pattern during neuronal development, participating in the regulation of neuronal expansion, growth, differentiation and regional pattern development. This review examines evidence for non-immunological roles of TNFRSF members in brain development, function and maintenance under normal physiological conditions. In addition, several aspects of brain function during inflammation will also be described, when illuminating and relevant to the non-immunological role of TNFRSF members. Finally, key questions in the field will be outlined.

Immune modulator CD70 as a potential cisplatin resistance predictive marker in ovarian cancer

OBJECTIVE

We have used mass-spectrometry (MS) based proteomics platform to identify cell surface proteins over-expressed on a cisplatin resistant derivative of an ovarian cancer cell line A2780.

METHODS

Membrane associated glycoproteins from A2780 and its cisplatin resistant derivative cell line, A2780cis, were processed for liquid chromatography (LC)-MS based analysis. The expression of proteins found at elevated levels in A2780cis cell line was confirmed using flow cytometry and Taqman analysis. The expression of these proteins was further evaluated in unrelated ovarian cancer cell lines using MS analysis and flow cytometry. Immunohistochemical (IHC) analysis was performed using ovarian tumor tissues to evaluate the protein density on the cell surface. Monoclonal antibodies were used in an alamar blue proliferation assay to examine the cytotoxic effects on cell proliferation in resistant cell lines.

RESULTS

Six proteins were identified by LC-MS as being over-expressed on cell surface of A2780cis cell line. Mass spectrometry and flow cytometry confirmed the over-expression of CD49f, CD70 and Her-2/neu in other cisplatin resistant ovarian cancer cell lines. Immunohistochemical analysis revealed that only CD70 was expressed at moderate levels in ovarian tumors. When cisplatin resistant ovarian cell lines A2780cis and SKOV-3 were treated with antibody against CD70, there was a significant decrease in cell proliferation.

CONCLUSION

Using a MS based proteomics approach we have shown that expression of CD70 is associated with cisplatin resistance in ovarian cancer cell lines. Follow-up examination of these tumor cell line findings in clinical tumor specimens with available pathology staging and cisplatin treatment history is warranted.

Preclinical characterization of SGN-70, a humanized antibody directed against CD70

PURPOSE

CD70 (CD27L) is a member of the tumor necrosis factor family aberrantly expressed on a number of hematologic malignancies and some carcinomas. CD70 expression on malignant cells coupled with its highly restricted expression on normal cells makes CD70 an attractive target for monoclonal antibody (mAb)-based therapies. We developed a humanized anti-CD70 antibody, SGN-70, and herein describe the antitumor activities of this mAb.

EXPERIMENTAL DESIGN

CD70 expression on primary tumors was evaluated by immunohistochemical staining of Hodgkin lymphoma, non-Hodgkin lymphoma, multiple myeloma, and renal cell carcinoma tissue microarrays. The CD70-binding and cytotoxic activities of SGN-70 were tested in vitro using a number of cell-based assays. The in vivo antitumor properties of SGN-70 were tested in severe combined immunodeficient mice bearing disseminated lymphoma and multiple myeloma xenografts. Mechanism-of-action studies were conducted using SGN-70v, a variant mAb with equivalent target-binding activity but impaired Fcgamma receptor binding compared with SGN-70.

RESULTS

Immunohistochemical analysis identified CD70 expression on approximately 40% of multiple myeloma isolates and confirmed CD70 expression on a high percentage of Hodgkin lymphoma Reed-Sternberg cells, non-Hodgkin lymphoma, and renal cell carcinoma tumors. SGN-70 lysed CD70+ tumor cells via Fc-dependent functions, including antibody-dependent cellular cytotoxicity and phagocytosis and complement fixation. In vivo, SGN-70 treatment significantly decreased tumor burden and prolonged survival of tumor-bearing mice.

CONCLUSIONS

SGN-70 is a novel humanized IgG1 mAb undergoing clinical development for the treatment of CD70+ cancers. SGN-70 possesses Fc-dependent antibody effector functions and mediates antitumor activity in vivo.

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.

Potent anticarcinoma activity of the humanized anti-CD70 antibody h1F6 conjugated to the tubulin inhibitor auristatin via an uncleavable linker

PURPOSE

The antitubulin agent monomethyl auristatin F (MMAF) induces potent antitumor effects when conjugated via protease cleavable linkers to antibodies targeting internalizing, tumor-specific cell surface antigens. Humanized 1F6 (h1F6) is a humanized monoclonal antibody targeting CD70, a member of the tumor necrosis factor family that is expressed on hematologic malignancies and carcinomas. Here, we tested h1F6-maleimidocaproyl (mc) MMAF conjugates, consisting of an uncleavable mc linker, for their ability to interfere with the growth of CD70-positive carcinomas.

EXPERIMENTAL DESIGN

To evaluate the optimal drug per antibody ratio, we conjugated either four or eight MMAF molecules to the cysteines that comprise the interchain disulfides of h1F6 and determined antitumor activities in vitro and in xenografted mice. The tumor types tested included glioblastoma, patient-derived renal cell carcinoma (RCC) cell isolates, and standard RCC tumor cell lines.

RESULTS

All h1F6-mcMMAF conjugates potently interfered with the growth of all carcinomas in vitro and resulted in complete responses of RCC tumors implanted orthotopically or s.c. in mice. In vitro, h1F6-mcMMAF(8) was generally more potent than h1F6-mcMMAF(4). However, h1F6-mcMMAF(4) displayed equal or better efficacy than h1F6-mcMMAF(8) when administered to tumor-bearing mice.

CONCLUSIONS

We showed that h1F6-mcMMAF conjugates inhibited the growth of human carcinomas and that increased drug loading, while improving potency in vitro, did not substantially affect the pharmacodynamic and pharmacokinetic properties in vivo. Based on these findings, h1F6-mcMMAF(4), designated SGN-75, has been identified as a potential antibody-drug conjugate for clinical development.

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.

Minor groove binder antibody conjugates employing a water soluble beta-glucuronide linker

The minor groove binder beta-glucuronide drug-linker 3 was constructed from amino CBI 1 and determined to be a substrate for Escherichia coli beta-glucuronidase (EC 3.2.1.31), resulting in facile drug release. Compound 3 was conjugated to mAbs cAC10 (anti-CD30) and h1F6 (anti-CD70) to give antibody-drug conjugates (ADCs) with potencies comparable to that of free drug 1. The ADCs were largely monomeric at intermediate loading levels (4-5drug/mAb), in contrast to highly aggregated p-aminobenzylcarbamate dipeptide-based ADCs of 1 previously reported. Significant levels of immunologic specificity were observed with cAC10-3 by comparing antigen positive versus negative cell lines and binding versus non-binding control ADCs. The water soluble beta-glucuronide linker is stable in plasma and effectively delivers drugs to target cells leading to potent cytotoxic activities.

CD70 (TNFSF7) is expressed at high prevalence in renal cell carcinomas and is rapidly internalised on antibody binding

In order to identify potential markers of renal cancer, the plasma membrane protein content of renal cell carcinoma (RCC)-derived cell lines was annotated using a proteomics process. One unusual protein identified at high levels in A498 and 786-O cells was CD70 (TNFSF7), a type II transmembrane receptor normally expressed on a subset of B, T and NK cells, where it plays a costimulatory role in immune cell activation. Immunohistochemical analysis of CD70 expression in multiple carcinoma types demonstrated strong CD70 staining in RCC tissues. Metastatic tissues from eight of 11 patients with clear cell RCC were positive for CD70 expression. Immunocytochemical analysis demonstrated that binding of an anti-CD70 antibody to CD70 endogenously expressed on the surface of A498 and 786-O cell lines resulted in the rapid internalisation of the antibody-receptor complex. Coincubation of the internalising anti-CD70 antibody with a saporin-conjugated secondary antibody before addition to A498 cells resulted in 50% cell killing. These data indicate that CD70 represents a potential target antigen for toxin-conjugated therapeutic antibody treatment of RCC.

Engineered anti-CD70 antibody with multiple effector functions exhibits in vitro and in vivo antitumor activities

Antigens expressed on malignant cells in the absence of significant expression on normal tissues are highly desirable targets for therapeutic antibodies. CD70 is a TNF superfamily member whose normal expression is highly restricted but is aberrantly expressed in hematologic malignancies including non-Hodgkin lymphoma (NHL), Hodgkin disease, and multiple myeloma. In addition, solid tumors such as renal cell carcinoma, nasopharyngeal carcinoma, thymic carcinoma, meduloblastoma, and glioblastoma express high levels of this antigen. To functionally target CD70-expressing cancers, a murine anti-CD70 monoclonal antibody was engineered to contain human IgG1 constant domains. The engineered antibody retained the binding specificity of the murine parent monoclonal antibody and was shown to induce Fc-mediated effector functions including antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis in vitro. Further, administration of this antibody significantly prolonged survival of severe combined immunodeficient (SCID) mice bearing CD70+ disseminated human NHL xenografts. Survival of these mice was dependent upon the activity of resident effector cells including neutrophils, macrophages, and natural killer (NK) cells. These data suggest that an anti-CD70 antibody, when engineered to contain human IgG1 constant domains, possesses effector cell–mediated antitumor activity and has potential utility for anticancer therapy.

Individualized markers optimize class prediction of microarray data

Background

Identification of molecular markers for the classification of microarray data is a challenging task. Despite the evident dissimilarity in various characteristics of biological samples belonging to the same category, most of the marker – selection and classification methods do not consider this variability. In general, feature selection methods aim at identifying a common set of genes whose combined expression profiles can accurately predict the category of all samples. Here, we argue that this simplified approach is often unable to capture the complexity of a disease phenotype and we propose an alternative method that takes into account the individuality of each patient-sample.

Results

Instead of using the same features for the classification of all samples, the proposed technique starts by creating a pool of informative gene-features. For each sample, the method selects a subset of these features whose expression profiles are most likely to accurately predict the sample's category. Different subsets are utilized for different samples and the outcomes are combined in a hierarchical framework for the classification of all samples. Moreover, this approach can innately identify subgroups of samples within a given class which share common feature sets thus highlighting the effect of individuality on gene expression.

Conclusion

In addition to high classification accuracy, the proposed method offers a more individualized approach for the identification of biological markers, which may help in better understanding the molecular background of a disease and emphasize the need for more flexible medical interventions.

Development and Properties of β-Glucuronide Linkers for Monoclonal Antibody−Drug Conjugates

A beta-glucuronide-based linker for attaching cytotoxic agents to monoclonal antibodies (mAbs) was designed and evaluated. We employed the cytotoxic auristatin derivatives MMAE (1a) and MMAF (1b) and doxorubicin propyloxazoline (DPO, 2) to give the beta-glucuronide drug-linkers 9a, 9b, and 17, respectively. Cysteine-quenched derivatives of 9b and 17 were determined to be substrates for E. coli beta-glucuronidase, resulting in facile drug release. The beta-glucuronide MMAF drug-linker 9b was highly stable in rat plasma with an extrapolated half-life of 81 days. Each drug-linker when conjugated to mAbs c1F6 (anti-CD70) and cAC10 (anti-CD30) gave monomeric antibody-drug conjugates (ADCs) with as many as eight drugs per mAb and had high levels of immunologically specific cytotoxic activity on cancer cell lines. cAC10-9a displayed pronounced antitumor activity in a subcutaneous Karpas 299 lymphoma tumor model. A single dose treatment led to cures in all animals at the 0.5 mg/kg dose level and above, and the conjugate was well tolerated at 100 mg/kg. In mice with subcutaneous renal cell carcinoma xenografts, the MMAF conjugate c1F6-9b was tolerated at 25 mg/kg and efficacious at 0.75 mg/kg. These results demonstrate that the beta-glucuronide linker system is an effective strategy for targeting cytotoxic agents providing ADCs with high degrees of efficacy at well-tolerated doses.

Anti-CD70 antibodies: a potential treatment for EBV+ CD70-expressing lymphomas

A monoclonal antibody (Rituximab) directed against the B-cell surface antigen, CD20, is increasingly used as a therapy for B-cell lymphomas. However, CD20 is expressed on all normal mature B cells and hence is not a specific tumor target. In contrast, CD70 is expressed on highly activated lymphocytes as well as on many B-cell and T-cell lymphomas but is not expressed on the great majority of B cells and T cells. In this report, we have explored the potential utility of anti-CD70 monoclonal antibodies for treatment of CD70+ EBV+ B-cell lymphomas. Using two Burkitt's lymphoma lines (Raji and Jijoye) that express surface CD70 and a CD70- Burkitt's lymphoma line (Akata), we show that two different monoclonal antibodies directed against human CD70 allow rabbit and human complement to kill EBV+ B cells in a CD70-dependent manner in vitro. In the absence of complement, neither anti-CD70 antibody induced in vitro killing of CD70+ cell lines. Importantly, i.p. injection of anti-CD70 antibodies also inhibited the growth of CD70+ Burkitt's lymphoma cells in severe combined immunodeficient mice but did not inhibit the growth of CD70- Burkitt's lymphoma cells. These results suggest that anti-CD70 antibodies may be useful for the treatment of CD70+ B-cell lymphomas.

Dipeptide-based highly potent doxorubicin antibody conjugates

Highly potent and novel derivatives of doxorubicin were linked to monoclonal antibodies (mAbs) for site-specific drug delivery. Drug linker 5 consisted of a dipeptide linker attached directly to the daunosamine nitrogen of the n-butyldiacetate doxorubicin derivative 2a. Upon hydrolysis of the peptide linker and acetate groups, the free daunosamine nitrogen is able to form the highly potent 2-pyrrolinodoxorubicin (3a). The second approach involved the use of an oxazolidine carbamate (13) to mask an activating aldehyde group until proteolytic hydrolysis releases 3a. Both drug linkers were shown to be substrates for the lysosomal enzyme cathepsin B. Each molecule was conjugated to the mAbs c1F6 (anti-CD70) and cAC10 (anti-CD30) to give potent drug conjugates against renal cell carcinoma and anaplastic large cell lymphoma cell lines, respectively. The activities were immunologically selective, since antigen negative cell lines were much less sensitive to treatment with the drug conjugates. The approaches described here for attaching highly potent doxorubicin derivatives to mAbs are novel and allow for control of drug stability while covalently bound to the delivery agent.

Matrix-degrading proteases ADAMTS4 and ADAMTS5 (disintegrins and metalloproteinases with thrombospondin motifs 4 and 5) are expressed in human glioblastomas

Brain tumors, in particular glioblastomas, have a high morbidity and mortality, mainly due to their invasive nature. A prerequisite for this invasiveness is cell migration based on increased expression of proteases digesting the extracellular matrix. Brevican, an important extracellular proteoglycan that is upregulated in glioblastomas, can be degraded by certain proteases. We demonstrate that in human glioblastomas secretory proteases like ADAMTS4 and ADAMTS5 (aggrecanases 1 and 2; ADAMTS = a disintegrin and metalloproteinase with thrombospondin motifs) are expressed on the mRNA and protein levels in considerable amounts. Real-time RT-PCR shows a higher levels of ADAMTS4 and 5 expressions in glioblastomas in situ, compared to cultured human glioblastoma cells. The upregulation of these proteases in vivo by cytokines may explain this difference. In vitro, transforming growth factor-beta induces ADAMTS4, but less ADAMTS5, and interleukin-1beta ADAMTS5, but not ADAMTS4. As demonstrated by immunohistochemistry and confocal microscopy in situ, ADAMTS5 expression is confined to proliferating glioblastoma cells of surgical tumor sections and with lower intensity to astroglial cells in normal brain sections, as opposed to brevican. In vitro, glioblastoma-derived ADAMTS5 degrades recombinant human brevican to several smaller fragments. Our results show that ADAMTS4 and 5 are upregulated on proliferating glioblastoma cells and these proteases may contribute to their invasive potential.

CD70: a new tumor specific biomarker for renal cell carcinoma

PURPOSE

To date there have been no specific tumor markers available for the differential diagnosis of renal cell carcinoma (RCC). In an earlier study we identified high RNA expression of CD70 in clear cell RCC. CD70 is a type II transmembrane protein belonging to the tumor necrosis factor family. It represents the ligand for CD27, a glycosylated transmembrane protein of the tumor necrosis factor receptor family. To our knowledge the function of CD70 in solid tumors is not known. In the current study we analyzed CD70 protein expression in different RCC subtypes.

MATERIALS AND METHODS

A total of 68 tumor samples of different histopathological subtypes were investigated by immunochemistry, including 41 clear cell, 19 papillary and 5 chromophobe RCCs, and 3 oncocytomas as well as their normal tissue counterparts. Immunochemistry was performed on frozen tissue samples using monoclonal antibody against CD70.

RESULTS

None of the normal kidney tissues showed CD70 expression. In contrast, all clear cell RCCs expressed CD70 at a high level. Positive immunostaining was observed in 1 papillary (5%) and in 1 chromophobe (20%) RCC. Five papillary tumor samples (26%) showed focal staining in less than 5% of cells. All other samples were negative for CD70.

CONCLUSIONS

Our study identified CD70 as a new specific tumor marker for clear cell RCC. This new marker can be used for differential diagnosis in cases of uncertain histological classification. The function of this protein in tumorigenesis and its use as a diagnostic marker in serum and urine or as a therapeutic tool must be investigated in further studies.

CD27 and CD70 in T cell and B cell activation

In vitro work has defined the TNF receptor family member CD27 as a T and B cell co-stimulatory molecule. Its activity is governed by the transient availability of its TNF-like ligand CD70 on lymphocytes and dendritic cells. Recent studies, enforcing or abrogating CD27 function by genetic or protein intervention in mouse models have revealed key contributions of the CD27-CD70 system to effector and memory T cell formation, which is probably based on improved cell survival. The stimulatory effects of CD27 on B cell function appear to oppose those of CD70, which also has a signaling role. Targeting CD27-CD70 for therapy is attractive but should take into account the fact that constitutive CD27 stimulation culminates in lethal immunodeficiency.

Design, synthesis, and in vitro evaluation of dipeptide-based antibody minor groove binder conjugates

Antibody-drug conjugates (ADCs) were prepared consisting of DNA minor groove binder drugs (MGBs) attached to monoclonal antibodies (mAbs) through peptide linkers designed to release drugs inside the lysosomes of target cells. The site of linker attachment on the MGB was at the 5-position on the B-ring, since model studies showed that attachment of an electron-withdrawing group (i.e., acyl, carbamoyl) at this position increased the stability of the molecule. Because of the hydrophobic nature of the MGBs, several measures were required to overcome their tendencies to induce mAb aggregation upon conjugation. This is exemplified in the series of ADCs containing the amino-CBI drug 1. Initial adducts were prepared using the peptide sequence valine-citrulline, attached to a self-immolative para-aminobenzyl carbamate spacer. The resulting ADCs were completely aggregated. Removal of the self-immolative spacer, introduction of a more hydrophilic valine-lysine sequence, and incorporation of a tetraethyleneglycol unit between the mAb and the peptide resulted in conjugates that were nonaggregated, even with as many as eight drugs per mAb. These results were extended to include the hydroxy aza-CBI drug 2, which was linked to the valine-lysine sequence through a para-aminobenzyl ether self-immolative spacer. The resulting mAb conjugates were monomeric and released the hydroxy aza-CBI drug upon treatment with human cathepsin B. In vitro cytotoxicity assays established that the mAb-MGB drug conjugates were highly cytotoxic and effected immunologically specific cell kill at subsaturating doses. The results provide a general strategy for MGB prodrug design and illustrate the importance of linker hydrophilicity in making nonaggregated, active mAb-MGB conjugates.

Signaling through CD70 regulates B cell activation and IgG production

CD70, the cellular ligand of the TNF receptor family member CD27, is expressed transiently on activated T and B cells and constitutively on a subset of B cell chronic lymphocytic leukemia and large B cell lymphomas. In the present study, we used B cells constitutively expressing CD70 to study the functional consequences of signaling through CD70. In vitro, CD70 ligation with anti-CD70 mAbs strongly supported proliferation and cell cycle entry of B cells submitogenically stimulated with either anti-CD40 mAb, LPS, or IL-4. In this process, the cell surface receptors CD25, CD44, CD69, CD95, and GL7 were up-regulated, whereas the expression of CD21, CD62L, surface IgM (sIgM), and sIgD was decreased. Addition of CD70 mAb to low dose LPS-stimulated CD70-positive B cells strongly diminished IgG secretion and enhanced production of IgM. Signaling through CD70 on B cells was dependent on the initiation of both PI3K and MEK pathways. In vivo exposure to either CD70 mAb or the CD70 counterreceptor CD27 down-regulated CD62L and sIgM on CD70-positive B cells. CD70 signaling during T cell-dependent immune responses also decreased IgG-specific Ab titers. Together, the in vitro and in vivo data demonstrate that CD70 has potent reverse signaling properties in B cells, initiating a signaling cascade that regulates expansion and differentiation.

Secretion of cytokines and growth factors as a general cause of constitutive NFkappaB activation in cancer

The constitutive activation of nuclear factor kappaB (NFkappaB) helps a variety of tumors to resist apoptosis and desensitizes them to chemotherapy, but the causes are still largely unknown. We have analysed this phenomenon in eight mutant cell lines derived from human 293 cells, selected for NFkappaB-dependent expression of a marker gene, and also in seven tumor-derived cell lines. Conditioned media from all of these cells stimulated the activation of NFkappaB (up to 30-fold) in indicator cells carrying an NFkappaB-responsive reporter. Therefore, secretion of extracellular factors as the cause of constitutive activation seems to be general. The mRNAs encoding several different cytokines and growth factors were greatly overexpressed in the tumor and mutant cells. The pattern of overexpression was distinct in each cell line, indicating that the phenomenon is complex. Two secreted factors whose roles in the constitutive activation of NFkappaB are not well defined were investigated further as pure proteins: transforming growth factor beta2 (TGFbeta2) and fibroblast growth factor 5 (FGF5) were both highly expressed in some mutant clones and tumor cell lines, each activated NFkappaB alone, and the combination was synergistic. Our data indicate that a group of different factors, expressed at abnormally high levels, can contribute singly and synergistically to the constitutive activation of NFkappaB in all of the mutant and tumor cell lines we studied. Since several NFkappaB target genes encode secreted proteins that induce NFkappaB, autocrine loops are likely to be ubiquitously important in the constitutive activation of NFkappaB in cancer. We provide the first evidence of the general, complex, and synergistic activation of NFkappaB in tumor and mutant cell lines through the action of secreted factors and suggest that the same explanation is likely for the constitutive activation of NFkappaB in cancers.

T-cell immune responses in the brain and their relevance for cerebral malignancies

In order that cellular immune responses afford protection without risk to sensitive normal tissue, they must be adapted to individual tissues of the body. Nowhere is this more critical than for the brain, where various passive and active mechanisms maintain a state of immune privilege that can limit high magnitude immune responses. Nevertheless, it is now clear that immune responses are induced to antigens in the brain, including those expressed by cerebral malignancies. We discuss hypotheses of how this can occur, although details such as which antigen presenting cells are involved remain to be clarified. Antitumor responses induced spontaneously are insufficient to eradicate malignant astrocytomas; many studies suggest that this can be explained by a combination of low level immune response induction and tumor mediated immunosuppression. A clinical objective currently pursued is to use immunotherapy to ameliorate antitumour immunity. This will necessitate a high level immune response to ensure sufficient effector cells reach the tumor bed, focused cytotoxicity to eradicate malignant cells with little collateral damage to critical normal cells, and minimal inflammation. To achieve these aims, priority should be given to identifying more target antigens in astrocytoma and defining those cells present in the brain parenchyma that are essential to maintain antitumour effector function without exacerbating inflammation. If we are armed with better understanding of immune interactions with brain tumor cells, we can realistically envisage that immunotherapy will one day offer hope to patients with currently untreatable neoplastic diseases of the CNS.

Impaired voltage-gated K+ channel expression in brain during experimental cancer cachexia

Cancer-induced cachexia affects most advanced cancer patients. It is characterized by anorexia, profound metabolic dysfunctions, and severe neurological disorders. Here we show that voltage-gated potassium channel (Kv) expression is impaired in the brain of tumor-bearing animals. Expression of both delayed rectifier (Kv1.1, Kv1.2, Kv1.3, Kv1.5, Kv1.6, Kv2.1, Kv3.1, Kv4.2) and A-type potassium channels (Kv1.4, Kv3.3, Kv3.4) was greatly down-regulated in brain from animals bearing a Yoshida AH-130 ascites hepatoma. The possible compensatory mechanisms (Kv1.4/Kv4.2), expression of redundant genes (Kv3.1/Kv3.3) and heteromultimeric channel formation (Kv2.1/Kv9.3) were also affected. The high circulating levels of TNFalpha and the reduced expression of the anti-apoptotic protein Bcl-XL found in the brain of tumor-bearing animals indicate that this response could be mediated by an increase in brain cell death due to apoptosis. The results suggest that brain function is impaired during cancer cachexia, and may account for the cancer-induced anorectic response and other neurological alterations.