NK Cell Therapeutics for Hematologic Malignancies: from Potential to Fruition.

Purpose Of Review: The current review focuses on the preclinical development and clinical advances of natural killer (NK) cell therapeutics for hematologic malignancies and offers perspective on the unmet challenges that will direct future discovery in the field.

Recent Findings: Approaches to improve or re-direct NK cell anti-tumor functions against hematologic malignancies have included transgenic expression of chimeric antigen receptors (CARs), administration of NK cell engagers including BiKEs and TriKEs that enhance antibody-dependent cellular cytotoxicity (ADCC) by co-engaging NK cell CD16 and antigens on tumors, incorporation of a non-cleavable CD16 that results in enhanced ADCC, use of induced memory-like NK cells alone or in combination with CARs, and blockade of NK immune checkpoints to enhance NK cytotoxicity. Recently reported and ongoing clinical trials support the feasibility and safety of these approaches.

Selectively targeting myeloid-derived suppressor cells through TRAIL receptor 2 to enhance the efficacy of CAR T cell therapy for treatment of breast cancer.

Background: Successful targeting of solid tumors such as breast cancer (BC) using chimeric antigen receptor (CAR) T cells has proven challenging, largely attributed to the immunosuppressive tumor microenvironment (TME). Myeloid-derived suppressor cells (MDSCs) inhibit CAR T cell function and persistence within the breast TME. To overcome this challenge, we have developed CAR T cells targeting tumor-associated mucin 1 (MUC1) with a novel chimeric costimulatory receptor that targets tumor necrosis factor-related apoptosis-inducing ligand receptor 2 (TR2) expressed on MDSCs.

Oncolytic adeno-immunotherapy modulates the immune system enabling CAR T-cells to cure pancreatic tumors.

High expression levels of human epidermal growth factor receptor 2 (HER2) have been associated with poor prognosis in patients with pancreatic adenocarcinoma (PDAC). However, HER2-targeting immunotherapies have been unsuccessful to date. Here we increase the breadth, potency, and duration of anti-PDAC HER2-specific CAR T-cell (HER2.

Design and Implementation of NK Cell-Based Immunotherapy to Overcome the Solid Tumor Microenvironment.

Natural killer (NK) cells are innate immune effectors capable of broad cytotoxicity via germline-encoded receptors and can have conferred cytotoxic potential via the addition of chimeric antigen receptors. Combined with their reduced risk of graft-versus-host disease (GvHD) and cytokine release syndrome (CRS), NK cells are an attractive therapeutic platform. While significant progress has been made in treating hematological malignancies, challenges remain in using NK cell-based therapy to combat solid tumors due to their immunosuppressive tumor microenvironments (TMEs).

Detection of response to tumor microenvironment-targeted cellular immunotherapy using nano-radiomics.

Immunotherapies, including cell-based therapies, targeting the tumor microenvironment (TME) result in variable and delayed responses. Thus, it has been difficult to gauge the efficacy of TME-directed therapies early after administration. We investigated a nano-radiomics approach (quantitative analysis of nanoparticle contrast-enhanced three-dimensional images) for detection of tumor response to cellular immunotherapy directed against myeloid-derived suppressor cells (MDSCs), a key component of TME.

Myeloid-Derived Suppressor Cells in the Tumor Microenvironment.

Myeloid-derived suppressor cells (MDSCs) represent a heterogenous population of immature myeloid cells capable of modulating immune responses. In the context of cancer, MDSCs are abnormally produced and recruited to the tumor microenvironment (TME) to aid in the establishment of an immunosuppressive TME that facilitates tumor escape. Additionally, MDSCs contribute to non-immunologic aspects of tumor biology, including tumor angiogenesis and metastasis.

NK Cells Expressing a Chimeric Activating Receptor Eliminate MDSCs and Rescue Impaired CAR-T Cell Activity against Solid Tumors.

Solid tumors are refractory to cellular immunotherapies in part because they contain suppressive immune effectors such as myeloid-derived suppressor cells (MDSCs) that inhibit cytotoxic lymphocytes. Strategies to reverse the suppressive tumor microenvironment (TME) should also attract and activate immune effectors with antitumor activity. To address this need, we developed gene-modified natural killer (NK) cells bearing a chimeric receptor in which the activating receptor NKG2D is fused to the cytotoxic ζ-chain of the T-cell receptor (NKG2D.

Chimeric Antigen Receptor Signaling Domains Differentially Regulate Proliferation and Native T Cell Receptor Function in Virus-Specific T Cells.

The efficacy of T cells expressing chimeric antigen receptors (CARs) for solid tumors has been limited by insufficient CAR T cell expansion and persistence. The use of virus-specific T cells (VSTs) as carriers for CARs may overcome this limitation since CAR-VSTs can be boosted by viral vaccines or oncolytic viruses. However, there is limited understanding of the optimal combination of endodomains and their influence on the native T cell receptor (TCR) in VSTs.

TGF-β1 programmed myeloid-derived suppressor cells (MDSC) acquire immune-stimulating and tumor killing activity capable of rejecting established tumors in combination with radiotherapy.

Cancer-induced myeloid-derived suppressor cells (MDSC) play an important role in tumor immune evasion. MDSC programming or polarization has been proposed as a strategy for leveraging the developmental plasticity of myeloid cells to reverse MDSC immune suppressive functions, or cause them to acquire anti-tumor activity. While MDSC derived from murine bone marrow precursor cells with tumor-conditioned medium efficiently suppressed T cell proliferation, MDSC derived from conditioned medium in presence of TGF-β1 (TGFβ-MDSC) acquired a novel immune-stimulatory phenotype, losing the ability to inhibit T cell proliferation and acquiring enhanced antigen-presenting capability.

Constitutive Signaling from an Engineered IL7 Receptor Promotes Durable Tumor Elimination by Tumor-Redirected T Cells.

Successful adoptive T-cell immunotherapy of solid tumors will require improved expansion and cytotoxicity of tumor-directed T cells within tumors. Providing recombinant or transgenic cytokines may produce the desired benefits but is associated with significant toxicities, constraining clinical use. To circumvent this limitation, we constructed a constitutively signaling cytokine receptor, C7R, which potently triggers the IL7 signaling axis but is unresponsive to extracellular cytokine.

MICA-Expressing Monocytes Enhance Natural Killer Cell Fc Receptor-Mediated Antitumor Functions.

Natural killer (NK) cells are large granular lymphocytes that promote the antitumor response via communication with other cell types in the tumor microenvironment. Previously, we have shown that NK cells secrete a profile of immune stimulatory factors (e.g.

Large-Scale Culture and Genetic Modification of Human Natural Killer Cells for Cellular Therapy.

Recent advances in methods for the ex vivo expansion of human natural killer (NK) cells have facilitated the use of these powerful immune cells in clinical protocols. Further, the ability to genetically modify primary human NK cells following rapid expansion allows targeting and enhancement of their immune function. We have successfully adapted an expansion method for primary NK cells from peripheral blood mononuclear cells or from apheresis products in gas permeable rapid expansion devices (G-Rexes).

Gene expression profiling of the human natural killer cell response to Fc receptor activation: unique enhancement in the presence of interleukin-12.

Background: Traditionally, the CD56(dim)CD16(+) subset of Natural Killer (NK) cells has been thought to mediate cellular cytotoxicity with modest cytokine secretion capacity. However, studies have suggested that this subset may exert a more diverse array of immunological functions. There exists a lack of well-developed functional models to describe the behavior of activated NK cells, and the interactions between signaling pathways that facilitate effector functions are not well understood.

Colocalization of the IL-12 receptor and FcgammaRIIIa to natural killer cell lipid rafts leads to activation of ERK and enhanced production of interferon-gamma.

Natural killer (NK) cells express an activating receptor for the Fc portion of IgG (FcgammaRIIIa) that mediates interferon (IFN)-gamma production in response to antibody (Ab)-coated targets. We have previously demonstrated that NK cells activated with interleukin-12 (IL-12) in the presence of immobilized IgG secrete 10-fold or more higher levels of IFN-gamma as compared with stimulation with either agent alone. We examined the intracellular signaling pathways responsible for this synergistic IFN-gamma production.

Interleukin-21 enhances NK cell activation in response to antibody-coated targets.

NK cells express an activating FcR (FcgammaRIIIa) that mediates Ab-dependent cellular cytotoxicity and the production of immune modulatory cytokines in response to Ab-coated targets. IL-21 has antitumor activity in murine models that depends in part on its ability to promote NK cell cytotoxicity and IFN-gamma secretion. We hypothesized that the NK cell response to FcR stimulation would be enhanced by the administration of IL-21.

Natural killer cells produce T cell-recruiting chemokines in response to antibody-coated tumor cells.

In the current report, we have examined the ability of natural killer (NK) cells to produce T cell-recruiting chemokines following dual stimulation with interleukin (IL)-2 or IL-12 and human breast cancer cells coated with an antitumor antibody (trastuzumab). NK cells stimulated in this manner secreted an array of T cell-recruiting chemotactic factors, including IL-8, macrophage-derived chemokine, macrophage inflammatory protein 1alpha (MIP-1alpha), monocyte chemoattractant protein 1, and regulated on activation, normal T-cell expressed and secreted (RANTES), whereas stimulation of NK cells with either agent alone had minimal effect. Furthermore, these factors were functional for T-cell chemotaxis as culture supernatants derived from costimulated NK cells induced migration of both naïve and activated T cells in an in vitro chemotaxis assay.

Phase I study of the sequential combination of interleukin-12 and interferon alfa-2b in advanced cancer: evidence for modulation of interferon signaling pathways by interleukin-12.

Purpose: To evaluate the safety of sequentially administered recombinant (r) human (h) interleukin-12 (IL-12) and interferon alfa-2b (IFN-alpha-2b) in patients with advanced cancer and to determine the effects of endogenously produced IFN-gamma on Janus kinase-signal transducer and activator of transcription (Jak-STAT) signal transduction in patient peripheral-blood mononuclear cells (PBMCs).

Patients And Methods: Forty-nine patients with metastatic cancer received rhIL-12 on day 1 and IFN-alpha-2b on days 2 to 6 of either a 14-day (n = 43) or a 7-day treatment cycle (n = 6). rhIL-12 was initially administered subcutaneously at a dose of 100 ng/kg, whereas IFN-alpha-2b was escalated from 1 to 10 million units (MU) in cohorts of three patients (1, 3, 5, 7, or 10 MU).

Src homology 2-containing inositol 5'-phosphatase 1 negatively regulates IFN-gamma production by natural killer cells stimulated with antibody-coated tumor cells and interleukin-12.

We have previously shown that natural killer (NK) cells secrete a distinct profile of immunomodulatory cytokines in response to dual stimulation with antibody-coated tumor cells and interleukin-12 (IL-12). This NK cell cytokine response is dependent on synergistic signals mediated by the activating receptor for the Fc portion of IgG (FcgammaRIIIa) and the IL-12 receptor (IL-12R), both constitutively expressed on NK cells. The phosphatase Src homology 2-containing inositol 5'-phosphatase 1 (SHIP1) is known to exert inhibitory effects on Fc receptor (FcR) signaling via its enzymatic activity on phosphatidylinositol 3-kinase (PI3-K) products within many cells of the immune system, most notably mast cells, B cells, and monocytes.

CpG-containing oligodeoxynucleotides act through TLR9 to enhance the NK cell cytokine response to antibody-coated tumor cells.

Bacterial DNA contains a high frequency of unmethylated CpG motifs that stimulate immune cells via TLR9. NK cells express a low-affinity activating receptor for the Fc portion of IgG (FcgammaRIIIa), but were not thought to express TLR9 protein. The direct response of NK cells to CpG oligodeoxynucleotides (ODN) in the presence of FcR stimulation was investigated.

Prolonged culture of vaccine-primed lymphocytes results in decreased antitumor killing and change in cytokine secretion.

Adoptive transfer of effector T cells has been used successfully to eliminate metastases in animal models. Because antitumor activity depends on the number of effector cells transferred, some human trials have used in vitro-repetitive activation and expansion techniques to increase cell number. We hypothesized that the prolonged culture period might contribute to the lack of human trial success by decreasing the potency of the effector T cells.

Differential expression of SHIP1 in CD56bright and CD56dim NK cells provides a molecular basis for distinct functional responses to monokine costimulation.

Monocyte cytokines (ie, monokines) induce natural killer (NK) cells to produce interferon-gamma (IFN-gamma), which is critical for monocyte clearance of infectious pathogens and tumor surveillance. Human CD56bright NK cells produce far more IFN-gamma in response to monokines than do CD56dim NK cells. The kinases and phosphatases involved in regulating IFN-gamma production by monokine-activated NK cells are not clearly identified.