Chimeric antigen receptor-engineered cytokine-induced killer cells overcome treatment resistance of pre-B-cell acute lymphoblastic leukemia and enhance survival.

Pre-emptive cancer immunotherapy by donor lymphocyte infusion (DLI) using cytokine-induced killer (CIK) cells may be beneficial to prevent relapse with a reduced risk of causing graft-versus-host-disease. CIK cells are a heterogeneous effector cell population including T cells (CD3(+) CD56(-) ), natural killer (NK) cells (CD3(-) CD56(+) ) and natural killer T (T-NK) cells (CD3(+) CD56(+) ) that exhibit non-major histocompatibility complex (MHC)-restricted cytotoxicity and are generated by ex vivo expansion of peripheral blood mononuclear cells in the presence of interferon (IFN)-γ, anti-CD3 antibody, interleukin-2 (IL-2) and interleukin-15 (IL-15). To facilitate selective target-cell recognition and enhance specific cytotoxicity against B-cell acute lymphoblastic leukemia (B-ALL), we transduced CIK cells with a lentiviral vector encoding a chimeric antigen receptor (CAR) that carries a composite CD28-CD3ζ domain for signaling and a CD19-specific scFv antibody fragment for cell binding (CAR 63.28.z). In vitro analysis revealed high and specific cell killing activity of CD19-targeted CIK/63.28.z cells against otherwise CIK-resistant cancer cell lines and primary B-ALL blasts, which was dependent on CD19 expression and CAR signaling. In a xenograft model in immunodeficient mice, treatment with CIK/63.28.z cells in contrast to therapy with unmodified CIK cells resulted in complete and durable molecular remissions of established primary pre-B-ALL. Our results demonstrate potent antileukemic activity of CAR-engineered CIK cells in vitro and in vivo, and suggest this strategy as a promising approach for adoptive immunotherapy of refractory pre-B-ALL.

A bispecific transmembrane antibody simultaneously targeting intra- and extracellular epitopes of the epidermal growth factor receptor inhibits receptor activation and tumor cell growth.

Epidermal growth factor receptor (EGFR) plays an important role in essential cellular processes such as proliferation, survival and migration. Aberrant activation of EGFR is frequently found in human cancers of various origins and has been implicated in cancer pathogenesis. The therapeutic antibody cetuximab (Erbitux) inhibits tumor growth by binding to the extracellular domain of EGFR, thereby preventing ligand binding and receptor activation. This activity is shared by the single chain antibody fragment scFv(225) that contains the same antigen binding domain. The unrelated EGFR-specific antibody fragment scFv(30) binds to the intracellular domain of the receptor and retains antigen binding upon expression as an intrabody in the reducing environment of the cytosol. Here, we used scFv(225) and scFv(30) domains to generate a novel type of bispecific transmembrane antibody termed 225.TM.30, that simultaneously targets intra- and extracellular EGFR epitopes. Bispecific 225.TM.30 and related membrane-anchored monospecific 225.TM and TM.30 proteins carrying extracellular scFv(225) or intracellular scFv(30) antibody fragments linked to a transmembrane domain were expressed in EGFR-overexpressing tumor cells using a doxycycline-inducible retroviral system. Induced expression of 225.TM.30 and 225.TM, but not TM.30 reduced EGFR surface levels and ligand-induced EGFR activation, while all three molecules markedly inhibited tumor cell growth. Co-localization of 225.TM with EGFR was predominantly found on the cell surface, while interaction with 225.TM.30 and TM.30 proteins resulted in the redistribution of EGFR to perinuclear compartments. Our data demonstrate functionality of this novel type of membrane-anchored intrabodies in tumor cells and suggest distinct modes of action of mono- and bispecific variants.

Tumor-derived GDF-15 blocks LFA-1 dependent T cell recruitment and suppresses responses to anti-PD-1 treatment.

Immune checkpoint blockade therapy is beneficial and even curative for some cancer patients. However, the majority don't respond to immune therapy. Across different tumor types, pre-existing T cell infiltrates predict response to checkpoint-based immunotherapy. Based on in vitro pharmacological studies, mouse models and analyses of human melanoma patients, we show that the cytokine GDF-15 impairs LFA-1/ß2-integrin-mediated adhesion of T cells to activated endothelial cells, which is a pre-requisite of T cell extravasation. In melanoma patients, GDF-15 serum levels strongly correlate with failure of PD-1-based immune checkpoint blockade therapy. Neutralization of GDF-15 improves both T cell trafficking and therapy efficiency in murine tumor models. Thus GDF-15, beside its known role in cancer-related anorexia and cachexia, emerges as a regulator of T cell extravasation into the tumor microenvironment, which provides an even stronger rationale for therapeutic anti-GDF-15 antibody development.

Dual targeting of glioblastoma with chimeric antigen receptor-engineered natural killer cells overcomes heterogeneity of target antigen expression and enhances antitumor activity and survival.

Epidermal growth factor receptor (EGFR) and its mutant form EGFRvIII are overexpressed in a large proportion of glioblastomas (GBM). Immunotherapy with an EGFRvIII-specific vaccine has shown efficacy against GBM in clinical studies. However, immune escape by antigen-loss variants and lack of control of EGFR wild-type positive clones limit the usefulness of this approach. Chimeric antigen receptor (CAR)-engineered natural killer (NK) cells may represent an alternative immunotherapeutic strategy. For targeting to GBM, we generated variants of the clinically applicable human NK cell line NK-92 that express CARs carrying a composite CD28-CD3ζ domain for signaling, and scFv antibody fragments for cell binding either recognizing EGFR, EGFRvIII, or an epitope common to both antigens. In vitro analysis revealed high and specific cytotoxicity of EGFR-targeted NK-92 against established and primary human GBM cells, which was dependent on EGFR expression and CAR signaling. EGFRvIII-targeted NK-92 only lysed EGFRvIII-positive GBM cells, while dual-specific NK cells expressing a cetuximab-based CAR were active against both types of tumor cells. In immunodeficient mice carrying intracranial GBM xenografts either expressing EGFR, EGFRvIII or both receptors, local treatment with dual-specific NK cells was superior to treatment with the corresponding monospecific CAR NK cells. This resulted in a marked extension of survival without inducing rapid immune escape as observed upon therapy with monospecific effectors. Our results demonstrate that dual targeting of CAR NK cells reduces the risk of immune escape and suggest that EGFR/EGFRvIII-targeted dual-specific CAR NK cells may have potential for adoptive immunotherapy of glioblastoma.

ErbB2/HER2-Specific NK Cells for Targeted Therapy of Glioblastoma.

BACKGROUND: Glioblastoma (GBM) is the most common and malignant intracranial tumor in adults and currently incurable. To specifically target natural killer (NK) cell activity to GBM, we employed NK-92/5.28.z cells that are continuously expanding human NK cells expressing an ErbB2-specific chimeric antigen receptor (CAR). METHODS: ErbB2 expression in 56 primary tumors, four primary cell cultures, and seven established cell lines was assessed by immunohistochemistry and flow cytometry. Cell killing activity of NK-92/5.28.z cells was analyzed in in vitro cytotoxicity assays. In vivo antitumor activity was evaluated in NOD-SCID IL2Rγ(null) (NSG) mice carrying orthotopic human GBM xenografts (6 to 11 mice per group) and C57BL/6 mice carrying subcutaneous and orthotopic ErbB2-expressing murine GBM tumors (5 to 8 mice per group). Statistical tests were two-sided. RESULTS: We found elevated ErbB2 protein expression in 41% of primary GBM samples and in the majority of GBM cell lines investigated. In in vitro assays, NK-92/5.28.z in contrast to untargeted NK-92 cells lysed all ErbB2-positive established and primary GBM cells analyzed. Potent in vivo antitumor activity of NK-92/5.28.z was observed in orthotopic GBM xenograft models in NSG mice, leading to a marked extension of symptom-free survival upon repeated stereotactic injection of CAR NK cells into the tumor area (median survival of 200.5 days upon treatment with NK-92/5.28.z vs 73 days upon treatment with parental NK-92 cells, P < .001). In immunocompetent mice, local therapy with NK-92/5.28.z cells resulted in cures of transplanted syngeneic GBM in four of five mice carrying subcutaneous tumors and five of eight mice carrying intracranial tumors, induction of endogenous antitumor immunity, and long-term protection against tumor rechallenge at distant sites. CONCLUSIONS: Our data demonstrate the potential of ErbB2-specific NK-92/5.28.z cells for adoptive immunotherapy of glioblastoma, justifying evaluation of this approach for the treatment of ErbB2-positive GBM in clinical studies.