Targeting CD33 in Chemoresistant AML Patient-Derived Xenografts by CAR-CIK Cells Modified with an Improved SB Transposon System.

The successful implementation of chimeric antigen receptor (CAR)-T cell therapy in the clinical context of B cell malignancies has paved the way for further development in the more critical setting of acute myeloid leukemia (AML). Among the potentially targetable AML antigens, CD33 is insofar one of the main validated molecules. Here, we describe the feasibility of engineering cytokine-induced killer (CIK) cells with a CD33.CAR by using the latest optimized version of the non-viral Sleeping Beauty (SB) transposon system "SB100X-pT4." This offers the advantage of improving CAR expression on CIK cells, while reducing the amount of DNA transposase as compared to the previously employed "SB11-pT" version. SB-modified CD33.CAR-CIK cells exhibited significant antileukemic activity in vitro and in vivo in patient-derived AML xenograft models, reducing AML development when administered as an "early treatment" and delaying AML progression in mice with established disease. Notably, by exploiting an already optimized xenograft chemotherapy model that mimics human induction therapy in mice, we demonstrated for the first time that CD33.CAR-CIK cells are also effective toward chemotherapy resistant/residual AML cells, further supporting its future clinical development and implementation within the current standard regimens.

Balance of Anti-CD123 Chimeric Antigen Receptor Binding Affinity and Density for the Targeting of Acute Myeloid Leukemia.

Chimeric antigen receptor (CAR)-redirected T lymphocytes are a promising immunotherapeutic approach and object of pre-clinical evaluation for the treatment of acute myeloid leukemia (AML). We developed a CAR against CD123, overexpressed on AML blasts and leukemic stem cells. However, potential recognition of low CD123-positive healthy tissues, through the on-target, off-tumor effect, limits safe clinical employment of CAR-redirected T cells. Therefore, we evaluated the effect of context-dependent variables capable of modulating CAR T cell functional profiles, such as CAR binding affinity, CAR expression, and target antigen density. Computational structural biology tools allowed for the design of rational mutations in the anti-CD123 CAR antigen binding domain that altered CAR expression and CAR binding affinity without affecting the overall CAR design. We defined both lytic and activation antigen thresholds, with early cytotoxic activity unaffected by either CAR expression or CAR affinity tuning but later effector functions impaired by low CAR expression. Moreover, the anti-CD123 CAR safety profile was confirmed by lowering CAR binding affinity, corroborating CD123 is a good therapeutic target antigen. Overall, full dissection of these variables offers suitable anti-CD123 CAR design optimization for the treatment of AML.

Donor-derived CD19-targeted T cells in allogeneic transplants.

PURPOSE OF REVIEW: Allogeneic hematopoietic stem cell transplantation (HSCT) is still partially ineffective in curing high-risk hematological malignancies, with estimates of relapse rates ranging from 40 to 50%. The purpose of this review is to discuss the emerging therapeutic options for patients with relapsed disease following HSCT based on adoptive immunotherapy using donor-derived T cells genetically engineered to express CD19-specific chimeric antigen receptors (CARs). RECENT FINDINGS: Adoptive cell therapy (ACT) with CAR-modified T cells represents an attractive therapeutic option for further enhancing the graft-versus-leukemia effect. However, CAR-modified T cells are often obtained using apheresis products collected from the patient's own blood, a procedure that has hindered the application of CAR-based therapies into the clinic. Alternative approaches rely on CAR T cells derived from donors rather than the patient's own blood. Therefore, it appears that overcoming the practical limitation of allogeneic T cell-induced graft versus-host-disease is a key to providing access to CAR immunotherapy to all eligible patients. SUMMARY: Donor-derived CD19-CAR T cells may advance the field of CAR immunotherapy by controlling relapse in leukemic patients and improving the range of applications of ACT protocols.

Acute myeloid leukemia and novel biological treatments: monoclonal antibodies and cell-based gene-modified immune effectors.

In the context of acute myeloid leukemia (AML) treatment, the interface between chemotherapy and immunotherapy is at present getting closer as never before. Scientific research is oriented in overcoming the main limits of actual chemotherapeutic regimens against AML, which still accounts for a considerable number of relapsed or resistant forms. A lot of investments have been done in the use of monoclonal antibodies (mAbs) and recently gene-modified immune cells have been considered as an alternative approach whenever chemotherapy fails to eradicate the disease. In this sense, AML is a potential suitable target for immunotherapeutic approaches, due to overexpression of several tumor antigens. Here we describe the state of the art of mAbs and cellular therapies employing engineered immune effectors, developed against specific AML antigens, in a window embracing preclinical research and translational studies to the clinical setting.

Differentiation of type 1 T regulatory cells (Tr1) by tolerogenic DC-10 requires the IL-10-dependent ILT4/HLA-G pathway.

Type 1 T regulatory (Tr1) cells suppress immune responses in vivo and in vitro and play a key role in maintaining tolerance to self- and non-self-antigens. Interleukin-10 (IL-10) is the crucial driving factor for Tr1 cell differentiation, but the molecular mechanisms underlying this induction remain unknown. We identified and characterized a subset of IL-10-producing human dendritic cells (DCs), termed DC-10, which are present in vivo and can be induced in vitro in the presence of IL-10. DC-10 are CD14(+), CD16(+), CD11c(+), CD11b(+), HLA-DR(+), CD83(+), CD1a(-), CD1c(-), express the Ig-like transcripts (ILTs) ILT2, ILT3, ILT4, and HLA-G antigen, display high levels of CD40 and CD86, and up-regulate CD80 after differentiation in vitro. DC-10 isolated from peripheral blood or generated in vitro are potent inducers of antigen-specific IL-10-producing Tr1 cells. Induction of Tr1 cells by DC-10 is IL-10-dependent and requires the ILT4/HLA-G signaling pathway. Our data indicate that DC-10 represents a novel subset of tolerogenic DCs, which secrete high levels of IL-10, express ILT4 and HLA-G, and have the specific function to induce Tr1 cells.

Role of human leukocyte antigen-G in the induction of adaptive type 1 regulatory T cells.

Adaptive type 1 regulatory T (Tr1) cells are suppressor cells characterized by the production of interleukin (IL)-10 in the absence of IL-4. IL-10 is essential not only for suppression of effector cells by Tr1 cells, but also for their differentiation in vitro and in vivo. However, little is known on the molecular mechanisms underneath the IL-10-mediated induction of Tr1 cells. Human Leukocyte Antigen (HLA)-G, a non-classical HLA class I molecule, has both direct inhibitory effects on natural killer cells, dendritic cells (DC), and T cells and long-term tolerogenic indirect effects by inducing regulatory T (Tr) cells. In the present review, we discuss current findings on Tr-cell induction by the different isoforms of HLA-G, focusing on the relationship among HLA-G, its ligands, and IL-10. We recently described a subset of human DC, termed DC-10, that express high levels of HLA-G and ILT4, secrete high amounts of IL-10, and induce allospecific Tr1 cells in vitro via an IL-10-dependent ILT4/HLA-G pathway. IL-10, HLA-G, and ILT4 may also be involved in Tr1-cell induction in vivo. Overall, these data demonstrate that cross-regulation between IL-10 and HLA-G may be instrumental for Tr1-cell induction and tolerance.