Chimeric antigen receptor (CAR) T-cell therapy has been shown to be dramatically effective in the treatment of B-cell malignancies. However, there are still substantial obstacles to overcome, before similar responses can be achieved in patients with solid tumors. We evaluated both in vitro and in a preclinical murine model the efficacy of different 2nd and 3rd generation CAR constructs targeting GD2, a disial-ganglioside expressed on the surface of neuroblastoma (NB) tumor cells. In order to address potential safety concerns regarding clinical application, an inducible safety switch, namely inducible Caspase-9 (iC9), was also included in the vector constructs. Our data indicate that a 3rd generation CAR incorporating CD28.4-1BB costimulatory domains is associated with improved anti-tumor efficacy as compared with a CAR incorporating the combination of CD28.OX40 domains. We demonstrate that the choice of 4-1BB signaling results into significant amelioration of several CAR T-cell characteristics, including: 1) T-cell exhaustion, 2) basal T-cell activation, 3) in vivo tumor control and 4) T-cell persistence. The fine-tuning of T-cell culture conditions obtained using IL7 and IL15 was found to be synergic with the CAR.GD2 design in increasing the anti-tumor activity of CAR T cells. We also demonstrate that activation of the suicide gene iC9, included in our construct without significantly impairing neither CAR expression nor anti-tumor activity, leads to a prompt induction of apoptosis of GD2.CAR T cells. Altogether, these findings are instrumental in optimizing the function of CAR T-cell products to be employed in the treatment of children with NB.

We developed an innovative and efficient, feeder-free culture method to genetically modify and expand peripheral blood-derived NK cells with high proliferative capacity, while preserving the responsiveness of their native activating receptors. Activated peripheral blood NK cells were efficiently transduced by a retroviral vector carrying a second-generation CAR targeting CD19. CAR expression was demonstrated across the different NK subsets. CAR.CD19-NK cells display higher anti-leukemic activity towards CD19 + cell lines and primary blasts obtained from patients with B-cell precursor ALL compared to unmodified NK cells. In vivo animal model data showed that the anti-leukemia activity of CAR.CD19-NK cell is superimposable to that of CAR-T cells, with a lower toxicity profile. These data support the feasibility of generating feeder-free expanded, genetically-modified peripheral blood NK cells for effective 'off-the-shelf' immuno-gene-therapy, while their innate alloreactivity can be safely harnessed to potentiate allogeneic cell therapy.

Class switch recombination (CSR) plays an important role in adaptive immune response by enabling mature B cells to switch from IgM expression to the expression of downstream isotypes. CSR is preceded by inducible germline (GL) transcription of the constant genes and is controlled by the 3′ regulatory region (3′RR) in a stimulus-dependent manner. Why the 3′RR-mediated upregulation of GL transcription is delayed to the mature B-cell stage is presently unknown. Here we show that mice devoid of an inducible CTCF binding element, located in the α constant gene, display a marked isotype-specific increase of GL transcription in developing and resting splenic B cells and altered CSR in activated B cells. Moreover, insertion of a GL promoter downstream of the CTCF insulator led to premature activation of the ectopic promoter. This study provides functional evidence that the 3′RR has a developmentally controlled potential to constitutively activate GL promoters but that this activity is delayed, at least in part, by the CTCF insulator, which borders a transcriptionally active domain established by the 3′RR in developing B cells. E xpression of complex loci is developmentally programmed or induced by specific stimuli and is often controlled by distant regulatory elements within relatively large chromatin domains. Transcriptional and architectural factors play an important role in the establishment and maintenance of these domains and facilitate long-range interactions between regulatory elements and target promoters (1, 2). The Ig heavy chain (IgH) locus is expressed in a lineage-and developmental stage-dependent manner. Various cis-acting elements including promoters, enhancers, and insulators control IgH locus expression and are engaged in multiple long-range interactions (3, 4).Factors such as YY1, PAX5, IKAROS, CTCF, and Cohesin play important roles in various aspects of long-range events at the IgH locus, including V(D)J recombination, CSR, and promoter/enhancer and enhancer/enhancer interactions (3-6). Multiple CTCF binding elements (CBEs) were reported along the IgH locus. The majority of these CBEs lie within the variable domain (7), and two CBEs were identified within the V H -D intergenic region (7-9). At the 3′ end of the locus, ∼10 CBEs were identified downstream of the 3′RR and are thought to delineate the 3′ border of the IgH locus (10). More recently, a discrete CBE was identified within the α constant gene (11), but its role in vivo is presently unknown.Upon antigen challenge, mature B cells can undergo CSR that allows B cells to change the heavy-chain constant domain of an IgM to IgG, IgE, or IgA. CSR to a particular isotype is induced by specific external stimuli, including antigens, mitogens, cytokines, and intercellular interactions. CSR is mediated by highly repetitive sequences called switch (S) sequences located upstream of the constant exons and is preceded by germline (GL) transcription of the S sequences that originates from GL promoters, named I promoters (12).The 3′RR is composed of four enhance...

Medulloblastoma is the most frequent malignant childhood brain tumor with a high morbidity.Identification of new therapeutic targets would be instrumental in improving patient outcomes. We evaluated the expression of the tumor-associated antigen PRAME in biopsies from 60 medulloblastoma patients. PRAME expression was detectable in 82% of tissues independent of molecular and histopathologic subgroups. High PRAME expression also correlated with worse overall survival. We next investigated the relevance of PRAME as a target for immunotherapy. Medulloblastoma cells were targeted using genetically modified T cells with a PRAME-specific TCR (SLL TCR T cells). SLL TCR T cells efficiently killed medulloblastoma HLA-A*02+ DAOY cells as well as primary HLA-A*02+ medulloblastoma cells. Moreover, SLL TCR T cells controlled tumor growth in an orthotopic mouse model of medulloblastoma. To prevent unexpected T cell-related toxicity, an inducible caspase 9 (iC9) gene was introduced in frame with the SLL TCR; this safety switch triggered prompt elimination of genetically-modified T cells. Altogether, these data indicate that T cells genetically modified with a high-affinity, PRAME-specific TCR and iC9 may represent a promising innovative approach for treating HLA-A*02+ medulloblastoma patients.

The costimulatory combination of CD28.OX40 is crucial for improving persistence, in vivo expansion and proliferation of CAR.CD30 T-cells upon tumor encounter. CAR.CD30 manufacturing process based on the use of IL7/IL15 is also of paramount importance to optimize the anti-lymphoma activity of CAR T cells.

Background Diffuse midline gliomas (DMG) H3K27M-mutant, including diffuse intrinsic pontine glioma (DIPG), are pediatric brain tumors associated with grim prognosis. Although GD2-CAR T-cells demonstrated significant anti-tumor activity against DMG H3K27M-mutant in vivo, a multimodal approach may be needed to more effectively treat patients. We investigated GD2 expression in DMG/DIPG and other pediatric high-grade gliomas (pHGG) and sought to identify chemical compounds that would enhance GD2-CAR T-cell anti-tumor efficacy. Methods Immunohistochemistry in tumor tissue samples and immunofluorescence in primary patient-derived cell lines were performed to study GD2 expression. We developed a high-throughput cell-based assay to screen 42 kinase inhibitors in combination with GD2-CAR T-cells. Cell viability, western blots, flow-cytometry, real time PCR experiments, DIPG 3D culture models and orthotopic xenograft model were applied to investigate the effect of selected compounds on DIPG cell death and CAR T-cell function. Results GD2 was heterogeneously, but widely, expressed in the tissue tested, while its expression was homogeneous and restricted to DMG/DIPG H3K27M-mutant cell lines. We identified dual IGF1R/IR antagonists, BMS-754807 and linsitinib, able to inhibit tumor cell viability at concentrations that do not affect CAR T-cells. Linsitinib, but not BMS-754807, decreases activation/exhaustion of GD2-CAR T-cells and increases their central memory profile. The enhanced anti-tumor activity of linsitinib/GD2-CAR T-cell combination was confirmed in DIPG models in vitro, ex vivo and in vivo. Conclusion Our study supports the development of IGF1R/IR inhibitors to be used in combination with GD2-CAR T-cells for treating patients affected by DMG/DIPG and, potentially, by pHGG.

BackgroundThe Intratumoral Microvessel Density (IMVD) is commonly used to quantify tumoral vascularization and is usually assessed by pan-endothelial markers, such as CD31. Endoglin (CD105) is a protein predominantly expressed in proliferating endothelium and the IMVD determined by this marker measures specifically the neovascularization. In this study, we investigated the CD105 expression in pediatric rhabdomyosarcoma and assessed the neovascularization by using the angiogenic ratio IMVD-CD105 to IMVD-CD31.MethodsParaffin-embedded archival tumor specimens were selected from 65 pediatric patients affected by rhabdomyosarcoma. The expression levels of CD105, CD31 and Vascular Endothelial Growth Factor (VEGF) were investigated in 30 cases (18 embryonal and 12 alveolar) available for this study. The IMVD-CD105 to IMVD-CD31 expression ratio was correlated with clinical and pathologic features of these patients.ResultsWe found a specific expression of endoglin (CD105) in endothelial cells of all the rhabdomyosarcoma specimens analyzed. We observed a significant positive correlation between the IMVD individually measured by CD105 and CD31. The CD105/CD31 expression ratio was significantly higher in patients with lower survival and embryonal histology. Indeed, patients with a CD105/CD31 expression ratio < 1.3 had a significantly increased OS (88%, 95%CI, 60%–97%) compared to patients with higher values (40%, 95%CI, 12%–67%). We did not find any statistical correlation among VEGF and EFS, OS and CD105/CD31 expression ratio.ConclusionCD105 is expressed on endothelial cells of rhabdomyosarcoma and represent a useful tool to quantify neovascularization in this tumor. If confirmed by further studies, these results will indicate that CD105 is a potential target for combined therapies in rhabdomyosarcoma.Electronic supplementary materialThe online version of this article (10.1186/s12885-017-3947-4) contains supplementary material, which is available to authorized users.

Based on the clinical success observed in acute lymphoblastic leukemia (ALL) with chimeric antigen receptor engineered T (CAR T), we hypothesized that combining the specificity of a CAR with the innate allo-reactivity of KIR-mismatched NK cells might provide a powerful tool for adoptive cell therapy. The use of a third-party bank of CAR-NK cells offers the advantage of an immediate availability to be exploited in the allogenic setting and could be associated with a lower toxicity profile than CAR-T cells. In order to overcome regulatory and manufacturing hurdles associated with generation of CAR-NK cells, we developed a feeder-free culture resulting in a 3.2-log expansion after 20 days of culture. Specifically, natural cytotoxicity receptors (NCR) expressed on NK cells are stimulated in the presence of pleiotropic cytokines and expanded in GMP grade bioreactors. Expanded NK cells from healthy donors preserve a high percentage of CD56+ CD57- cells (85±13%), associated with high proliferative capability, and maintain the surface expression and the responsiveness of NCR and CD16. We proved that NK cells generated from 10 different healthy donors have high ability to recognize and eliminate different tumor types, including acute myeloid leukemia (AML) and ALL. After genetic modification with a retroviral vector encoding a CAR specific for CD19 antigen, transduction of activated NK cells averaged 38%±15% and the CAR.CD19 expression was stable over extended in vitro culture (60 days). Detailed phenotypic characterization of CAR-NK cells showed that CAR expression was not limited to the more mature NKG2A-/KIR+ cells, but rather was distributed across different NK subsets. We also demonstrated that NK and CAR-NK cells display significant anti-leukemia activity towards CD19+ leukemia and lymphoma cell lines (LCL 721.221, DAUDI and BV173) and primary blasts obtained from patients with B-cell precursor ALL (Bcp-ALL). Co-culture experiments using a 1:5 E/T ratio, showed that, while the anti-tumor activity was already remarkable with non-modified effector NK cells (60±30%, 71±33% and 54±23% of residual LCL 721.221, DAUDI and BV173 cells, respectively; p<0.05 vs T cells), it reached the highest level when CAR-NK cells were used as effectors (7±9%, 16±30% and 22±16% of residual LCL 721.221, DAUDI and BV173 cells, respectively; p<0.05 vs non-transduced NK cells). Importantly, INF-g production was significantly lower upon CAR-NK activation compared to CAR-T cells (DAUDI 384±194 ng/ml vs 1860±678 ng/ml, p=0.002). Functional analysis on primary Bcp-ALL blasts, demonstrate that CAR-NK cells exert high degree of leukemia control (on average 2.1±2% vs 5.4±1.6% with non-modified NK cells as effectors; p=0.04). An in vivo model of leukemia xenograft immunodeficient mice was used to evaluate whether CAR-NK cells are associated with a lower toxicity profile compared to CAR-T cells. While the in vivo antileukemia activity was superimposable between CAR-T and CAR-NK cells (mouse bioluminenscence at 20 days, 4.9x105 vs 6.6x105 photons/second, respectively; p=n.s. Figure A), mice treated with two i.v. infusions (day 0 and day 15) of 10x106 CAR.CD19 NK cells had a 100% overall survival (OS of 5 out of 5 mice) at 50 days compared to 20% of mice (1 out of 5) receiving 10x106 CAR.CD19 T cells (Figure B; p=0.01). Cytokine plasma level monitoring, performed on day +7 and +30 after effector cell infusion in the absence of leukemia persistence (as evidenced by a lack of bioluminescence signal), showed that mice engrafted with CD19+ leukemia and treated with CAR.CD19-NK cells have lower levels of circulating hIFN-g cytokine compared to mice treated with CAR.CD19-T cells at both day 7 (42±82 vs 330±346 ng/ml; p=0.05) and day 30 (0.9±0.7 vs 4148±667 ng/ml; p=0.05). These in vitro and in vivo data demonstrate the feasibility of clinical scale feeder-free expansion of non-modified NK cells and stably transduced CAR-NK cells. Both non-modified and gene-modified cells were capable of significant tumor killing, suggesting a multi-modal adoptive cell approach to treatment of leukemia. Since NK cells have been shown to be safely used in third-party setting (St. Jude Children's Research Hospital, USA; NCT00640796), we suggest that ex-vivo expanded, feeder-free NK cells can be universally applied for 'off-the-shelf' immuno-gene-therapy, and that their innate allo-reactivity can be safely harnessed to potentiate allogeneic cell therapy. Figure. Figure. Disclosures Locatelli: Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; bluebird bio: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Miltenyi: Honoraria; Bellicum: Consultancy, Membership on an entity's Board of Directors or advisory committees.