CD44v6 as innovative sarcoma target for CAR-redirected CIK cells

Purpose of our study was to explore a new immunotherapy for high grade soft tissue sarcomas (STS) based on cytokine-induced killer cells (CIK) redirected with a chimeric antigen receptor (CAR) against the tumor-promoting antigen CD44v6. We aimed at generating bipotential killers, combining the CAR specificity with the intrinsic tumor-killing ability of CIK cells (CAR⁺.CIK). We set a patient-derived experimental platform. CAR⁺.CIK were generated by transduction of CIK precursors with a lentiviral vector encoding for anti-CD44v6-CAR. CAR⁺.CIK were characterized and assessed in vitro against multiple histotypes of patient-derived STS. The anti-sarcoma activity of CAR⁺.CIK was confirmed in a STS xenograft model. CD44v6 was expressed by 40% (11/27) of patient-derived STS. CAR⁺.CIK were efficiently expanded from patients (n = 12) and killed multiple histotypes of STS (including autologous targets, n = 4). The killing activity was significantly higher compared with unmodified CIK, especially at low effector/target (E/T) ratios: 98% vs 82% (E/T = 10:1) and 68% vs 26% (1:4), (p<0.0001). Specificity of tumor killing was confirmed by blocking with anti-CD44v6 antibody. CAR⁺.CIK produced higher amounts of IL6 and IFN-γ compared to control CIK. CAR⁺.CIK were highly active in mice bearing subcutaneous STS xenografts, with significant delay of tumor growth (p<0.0001) without toxicities.

We report first evidence of CAR⁺.CIK's activity against high grade STS and propose CD44v6 as an innovative target in this setting. CIK are a valuable platform for the translation of CAR-based strategies to challenging field of solid tumors. Our findings support the exploration of CAR⁺.CIK in clinical trials against high grade STS.

Clinical pharmacology of CAR-T cells: Linking cellular pharmacodynamics to pharmacokinetics and antitumor effects

Adoptive cell transfer of T cells genetically modified with tumor-reactive chimeric antigen receptors (CARs) is a rapidly emerging field in oncology, which in preliminary clinical trials has already shown striking antitumor efficacy. Despite these premises, there are still a number of open issues related to CAR-T cells, spanning from their exact mechanism of action (pharmacodynamics), to the factors associated with their in vivo persistence (pharmacokinetics), and, finally, to the relative contribution of each of the two in determining the antitumor effects and accompanying toxicities. In light of the unprecedented curative potential of CAR-T cells and of their predicted wide availability in the next few years, in this review we will summarize the current knowledge on the clinical pharmacology aspects of what is anticipated to be a brand new class of biopharmaceuticals to join the therapeutic armamentarium of cancer doctors.

SCT for severe autoimmune diseases: consensus guidelines of the European Society for Blood and Marrow Transplantation for immune monitoring and biobanking

Over the past 15 years, SCT has emerged as a promising treatment option for patients with severe autoimmune diseases (ADs). Mechanistic studies recently provided the proof-of-concept that restoration of immunological tolerance can be achieved by haematopoietic SCT in chronic autoimmunity through eradication of the pathologic, immunologic memory and profound reconfiguration of the immune system, that is, immune ‘resetting'. Nevertheless, a number of areas remain unresolved and warrant further investigation to refine our understanding of the underlying mechanisms of action and to optimize clinical SCT protocols. Due to the low number of patients transplanted in each centre, it is essential to adequately collect and analyse biological samples in a larger cohort of patients under standardized conditions. The European society for blood and marrow transplantation Autoimmune Diseases and Immunobiology Working Parties have, therefore, undertaken a joint initiative to develop and implement guidelines for ‘good laboratory practice' in relation to procurement, processing, storage and analysis of biological specimens for immune reconstitution studies in AD patients before, during and after SCT. The aim of this document is to provide practical recommendations for biobanking of samples and laboratory immune monitoring in patients with ADs undergoing SCT, both for routine supportive care purposes and investigational studies.

Sirolimus-based graft-versus-host disease prophylaxis promotes the in vivo expansion of regulatory T cells and permits peripheral blood stem cell transplantation from haploidentical donors

Hematopoietic stem cell transplantation (HSCT) from human leukocyte antigen (HLA) haploidentical family donors is a promising therapeutic option for high-risk hematologic malignancies. Here we explored in 121 patients, mostly with advanced stage diseases, a sirolimus-based, calcineurin-inhibitor-free prophylaxis of graft-versus-host disease (GvHD) to allow the infusion of unmanipulated peripheral blood stem cell (PBSC) grafts from partially HLA-matched family donors (TrRaMM study, Eudract 2007-5477-54). Conditioning regimen was based on treosulfan and fludarabine, and GvHD prophylaxis on antithymocyte globulin Fresenius (ATG-F), rituximab and oral administration of sirolimus and mycophenolate. Neutrophil and platelet engraftment occurred in median at 17 and 19 days after HSCT, respectively, and full donor chimerism was documented in patients' bone marrow since the first post-transplant evaluation. T-cell immune reconstitution was rapid, and high frequencies of circulating functional T-regulatory cells (Treg) were documented during sirolimus prophylaxis. Incidence of acute GvHD grade II-IV was 35%, and occurrence and severity correlated negatively with Treg frequency. Chronic GvHD incidence was 47%. At 3 years after HSCT, transpant-related mortality was 31%, relapse incidence 48% and overall survival 25%. In conclusion, GvHD prophylaxis with sirolimus-mycophenolate-ATG-F-rituximab promotes a rapid immune reconstitution skewed toward Tregs, allowing the infusion of unmanipulated haploidentical PBSC grafts.

Progress and prospects: graft-versus-host disease

Graft-versus-host disease (GvHD) is one of the major complications of allogeneic hematopoietic stem cell transplantation, an otherwise highly effective therapeutic modality for patients affected by hematological diseases. The main inducers of GvHD are alloreactive donor T cells, which recognize host antigens presented by recipient cells. The critical role of lymphocytes in GvHD is well documented by the observation that T-cell depletion from the graft prevents GvHD. Unfortunately, the removal of donor lymphocytes from the graft increases the incidence of disease relapse and life-threatening infectious complications. Gene transfer technologies are promising tools to manipulate donor T-cell immunity to enforce graft-versus-tumor/graft-versus-infection while preventing or controlling GvHD. For this purpose, several cell and gene transfer approaches have been investigated at the preclinical level and implemented in clinical trials.

Anti-beta2 glycoprotein I antibodies cause inflammation and recruit dendritic cells in platelet clearance

Scavenger phagocytes are mostly responsible for the in vivo clearance of activated or senescent platelets. In contrast to other particulate substrates, the phagocytosis of platelets does not incite proinflammatory responses in vivo. This study assessed the contribution of macrophages and dendritic cells (DCs) to the clearance of activated platelets. Furthermore, we verified whether antibodies against the beta2 Glycoprotein I (beta2GPI), which bind to activated platelets, influence the phenomenon. DCs did not per se intemalise activated platelets. In contrast, macrophages efficiently phagocytosed platelets. In agreement with the uneventful nature of the clearance of platelets in vivo, phagocytosing macrophages did not release IL-1beta, TNF-alpha, or IL-10, beta2GPI bound to activated platelets and was required for their recognition by anti-beta2GPI antibodies. DCs internalised platelets opsonised by anti-beta2GPI antibodies. The phagocytosis of opsonised platelets determined the release of TNF-alpha and IL-1beta by DCs and macrophages. Phagocytosing macrophages, but not DCs, secreted the antiinflammatory cytokine IL-10. We conclude that anti-beta2GPI antibodies cause inflammation during platelet clearance and shuttle platelet antigens to antigen presenting DCs.

Cytokine secretion associated with the clearance of apoptotic bodies in renal cell carcinoma patients

The factors determining the outcome of immunotherapy in metastatic renal cell carcinoma (RCC) patients remain elusive. Macrophages from normal donors that phagocytose apoptotic cells secrete the immunosuppressive cytokine IL-10 in vitro. Conversely, IL-10 genetic deletion enhances the immunogenicity of apoptotic tumor cells in vivo. Elevated pre-treatment levels of IL-10 are associated with an unfavorable outcome of RCC. We examined whether the ability to release IL-10 by macrophages from RCC patients that phagocytosed apoptotic cells correlated with the outcome of immunotherapy. To this aim, we derived macrophages from 30 patients with metastatic RCC and from 21 healthy subjects (11 sex- and age-matched healthy controls and 10 younger donors). Patients either had a clinical response after immunotherapy, with a median survival after treatment of more than 18 months (n = 16), or were beginning immunotherapy after diagnosis of metastatic disease (n = 14). Macrophages from responding patients challenged with apoptotic cells released significantly less IL-10 than controls (p = 0.0075) and recently diagnosed patients (p = 0.0198), as ascertained by a 2-sided Student's t-test. This was not because macrophages from responding patients lost the ability to secrete IL-10, because antibody opsonization of apoptotic cells rescued IL-10 secretion. In contrast, macrophages from all groups of donors released similar amounts of TNF-alpha. The failure in IL-10 secretion by engulfing macrophages of responding subjects may exalt the immunogenicity of dying tumor cells, contributing to the success of immunotherapy.

The long pentraxin PTX3 binds to apoptotic cells and regulates their clearance by antigen-presenting dendritic cells

Pentraxins are acute-phase proteins produced in vivo during inflammatory reactions. Classical short pentraxins, C-reactive protein, and serum amyloid P component are generated in the liver in response to interleukin (IL)-6. The long pentraxin PTX3 is produced in tissues under the control of primary proinflammatory signals, such as lipopolysaccharide, IL-1 beta, and tumor necrosis factor-alpha, which also promote maturation of dendritic cells (DCs). Cell death commonly occurs during inflammatory reactions. In this study, it is shown that PTX3 specifically binds to dying cells. The binding was dose dependent and saturable. Recognition was restricted to extranuclear membrane domains and to a chronological window after UV irradiation or after CD95 cross-linking-induced or spontaneous cell death in vitro. PTX3 bound to necrotic cells to a lesser extent. Human DCs failed to internalize dying cells in the presence of PTX3, while they took up normally soluble or inert particulate substrates. These results suggest that PTX3 sequesters cell remnants from antigen-presenting cells, possibly contributing to preventing the onset of autoimmune reactions in inflamed tissues. (Blood. 2000;96:4300-4306)

Anti-beta2 glycoprotein I antibodies prevent the De-activation of platelets and sustain their phagocytic clearance

Exposure to phosphatidylserine (PS) tags dying and senescent cells for removal and identifies activated platelets. In this study we followed the fate of PS-exposing platelets in the presence of antibodies purified from Systemic Lupus Erythematosus (SLE) and primary Anti-phospholipid Syndrome (APS) patients' sera by beta2GPI affinity chromatography. Thrombin-activated platelets exposed PS and associated to beta2GPI. Both events were required for recognition by antibodies. Human monocyte-derived macrophages phagocytosed activated platelets only. Each macrophage internalized an average of 3.16+/-0.2 platelets after 60 min at 37 degrees C. Phagocytosis did not increase after longer incubations (4.65+/-0.26 platelets internalized by each macrophage after 300 min). Recognition of platelets by anti-beta2GPI antibodies significantly increased phagocytosis (P< 0.01). Upon withdrawal of thrombin, platelets downregulated PS (PS exposure t(1/2): 242 min) and the ability to be recognized by macrophages. Purified beta2GPI bound to PS-exposing platelets (association t(1/2): 250 min). Phosphatidyl serine exposure and beta2GPI association had virtually identical kinetics. Antibody binding prolonged the exposure of the beta2GPI/PS complex (t(1/2): >1200 min). The ability to phagocytose opsonized platelets was accordingly sustained (5.3+/-0.2 opsonized platelets were internalized by each macrophage after 60 min and 9.4+/-0.3 after 300 min). Anti-beta2GPI antibodies therefore poise activated platelets in a PS-exposing status, preventing the recycling of their function and favoring their phagocytic clearance.

In vivo administration of GM-CSF promotes the clearance of apoptotic cells: effects on monocytes and polymorphonuclear leukocytes

The clearance of apoptotic cells is crucial to avoid chronic inflammation and autoimmunity. Little is known about the factors that regulate it in vivo. We show that granulocyte-macrophage colony-stimulating factor (GM-CSF) administration to carcinoma patients confers to their leukocytes a significantly higher ability to phagocytose apoptotic cells than before (P < 0.005). GM-CSF increased the concentration of monocytes and polymorphonuclear leukocytes in the peripheral blood and activated circulating polymorphonuclear leukocytes. Both effects abated early after treatment, whereas phagocytosis of apoptotic cells was still significantly higher after 18 days compared with basal values (P < 0.005 and P < 0.025 for monocytes and polymorphonuclear leukocytes, respectively). On in vitro phagocytosis of apoptotic cells monocytes, but not polymorphonuclear leukocytes, up-regulated MHC class II membrane expression. These findings are consistent with the possibility that GM-CSF endows both scavenger and antigen-presenting leukocytes with the ability to internalize apoptotic tumor cells.

uPA/uPAR system is active in immature dendritic cells derived from CD14+CD34+ precursors and is down-regulated upon maturation

We recently described a subset of peripheral CD14+CD34+ cells able to migrate across endothelial cell monolayers and differentiate into immunostimulatory dendritic cells (DC). In this paper we show that immature DC derived from CD14+CD34+ precursors are also capable of reverse transendothelial migration and extracellular matrix (ECM) invasion using the urokinase plasminogen activator receptor (uPAR). We found that these cells respond to macrophage-inflammatory protein (MIP)-1alpha, enhancing their ability to invade ECM and supporting the idea that immature DC are selectively recruited at the site of inflammation to expand the pool of APCs. Interestingly, MIP-1alpha was also capable of preventing the decreased matrix invasion observed by blocking uPAR, suggesting that the uPA/uPAR system and MIP-1alpha cooperate in driving immature DC migration through the subendothelial matrix. Upon exposure to maturating stimuli, such as TNF-alpha, CD14+CD34+-derived DC enhance their APC function and decrease the capacity of invading ECM; these changes are accompanied by altered expression and function of uPAR. Moreover, mature DC shift their sensitivity from MIP-1alpha to MIP-3beta, enhancing their transendothelial migration capability in response to the latter chemokine. Our data support the hypothesis that bloodborne DC can move through ECM toward the site of pathogen entry where they differentiate into fully mature APCs with their motility and function regulated by microenvironmental stimuli, including MIP-1alpha, MIP-3beta, and TNF-alpha.

Delayed clearance of apoptotic lymphoma cells allows cross-presentation of intracellular antigens by mature dendritic cells

Single cells are deleted from the midst of living tissue during normal turnover and embryogenesis. This event is not associated with inflammation or autoimmunity. Little is known of the clearance of apoptotic cells during dangerous situations, accompanied by extensive cell death and tissue damage: when macrophages are overwhelmed by apoptotic cells, other phagocytes, including immature dendritic cells (DCs), may become involved. DCs efficiently present antigens derived from the processing of internalized apoptotic bodies to class I- and class II-restricted T cells. Antigen presentation results either in T cell activation or in their functional blockade. The outcome is influenced by pro-inflammatory maturative signals: efficient T cell cross-priming requires fully mature DCs. Here we discuss in vitro data suggesting that the number of apoptotic cells that die at a given time influences DC maturation and therefore their ability to uptake antigens from apoptotic cells and cross-activate T lymphocytes.

Bystander apoptosis triggers dendritic cell maturation and antigen-presenting function

Physiologic cell death via apoptosis occurs without inflammation or autoimmunity. Here, we investigated the outcome of the interaction of apoptotic cells with dendritic cells (DCs), which are potent professional APCs. DCs internalized apoptotic cells and processed them for presentation to both MHC class I- and class II-restricted T cells with an efficiency that was dependent upon the number of apoptotic cells. The latter event was accompanied by the autocrine/paracrine secretion of IL-1beta and TNF-alpha, with eventual DC maturation. High numbers of apoptotic cells, mimicking a failure of their in vivo clearance, are therefore sufficient to trigger DC maturation and the presentation of intracellular Ags from apoptotic cells, even in the absence of exogenous "danger" signals.

CD14+ CD34+ peripheral blood mononuclear cells migrate across endothelium and give rise to immunostimulatory dendritic cells

We describe a subset of peripheral CD14+ cells, coexpressing the CD34 progenitor marker and able to migrate across endothelial cell monolayers. On culture with granulocyte-macrophage-CSF, this population differentiated into dendritic cells expressing CD83, CD80, HLA-DR(bright), CD86, and CD54. These dendritic cells were immunostimulatory, in that they induced proliferation of allogenic and tetanus toxoid-specific T lymphocytes. The CD14+ CD34+ population expressed higher levels of platelet endothelial cell adhesion molecule-1 (PECAM-1) and alpha4beta1 integrin than the CD14+ CD34- counterpart, being dull positive for other integrins. Using stably transfected PECAM-1+, VCAM-1+, or ICAM-1+ cells, we found that PECAM-1 and, to a lesser extent, VCAM-1, could support transmigration of CD14+ CD34+ cells, whereas the alphaL-ICAM-1 interaction was involved in cell adhesion. PECAM-1-driven transmigration was conceivably dependent on a haptotactic gradient, as it was reduced by 80% across NIH3T3 cells transfected with the PECAM-1-delta cyto deletion mutant. This mutant lacks the cytoplasmic tail and displays a reduced tendency to localize at the intercellular junctions, thus failing to form a molecular junctional gradient. Once differentiated, dendritic cells derived from CD14+ CD34+ precursors retained their transendothelial migratory capability, using both PECAM-1 and ICAM-1 for transmigration. We suggest that a subset of CD14+ CD34+ circulating leukocytes can localize to peripheral tissues and differentiate into functional dendritic cells, thus representing a functional reservoir of potential APC. PECAM-1, constitutively expressed on vascular endothelium, is likely to play a relevant role in the egress of this population from the bloodstream.