Chimeric antigen receptor-engineered natural killer cells: a promising cancer immunotherapy

The Power of Three: Nanomaterials for Natural Killer (NK) Cell Immunoengineering Maximize Their Potency if They Exploit Multireceptor Stimulation

Many emerging cancer treatments are immunotherapies that modulate Natural Killer- (NK) or T cell activation, posing a challenge to develop immunoengineering nanomaterials that improve on the performance of molecular reagents. In physiological activation, multiple immunoreceptors signal in consort; however, current biomaterials do not replicate this. Here, NK cells are created for the first time, activating bionanomaterials that stimulate >2 immunoreceptors. Nanoclusters of monoclonal antibodies (mAb), templated by nanoscale graphene oxide sheets (NGO) (≈75 nm size), are exploited. To inform nanoreagent design, a model system of planar substrates with anchored mAb is first investigated. Combining mAb that stimulates three NK cell activating receptors (αNKP46 + αNKG2D + αDNAM-1), activated NK cells act more potently than any single receptor or pair. Applying this insight, an NGO-mAb nanocluster combining three distinct mAb: NGO-mAb(αNKP46 + αNKG2D + αDNAM-1) is created. This construct is potent and outperforms single-receptor-simulating nanoclusters, activating nearly twice as many NK cells as NGO-mAb(αNKP46) at a similar mAb dose or delivering similar activation at 10× lower dosage. Further, NGO-mAb are more potent than planar substrates for both single- and triple-mAb stimulation. These results imply a new concept for immunoengineering biomaterials: both nanoclustering and multi-receptor stimulation should be incorporated for maximum effect.

Comparable transforming growth factor beta-mediated immune suppression in ex vivo-expanded natural killer cells from cord blood and peripheral blood: implications for adoptive immunotherapy

T cell-based therapies like genetically modified immune cells expressing chimeric antigen receptors have shown robust anti-cancer activity in vivo, especially in patients with blood cancers. However, extending this approach to an "off-the-shelf" setting can be challenging, as allogeneic T cells carry a significant risk of graft-versus-host disease (GVHD). By contrast, allogeneic natural killer (NK) cells recognize malignant cells without the need for prior antigen exposure and have been used safely in multiple cancer settings without the risk of GVHD. However, similar to T cells, NK cell function is negatively impacted by tumor-induced transforming growth factor beta (TGF-β) secretion, which is a ubiquitous and potent immunosuppressive mechanism employed by most malignancies. Allogeneic NK cells for adoptive immunotherapy can be sourced from peripheral blood (PB) or cord blood (CB), and the authors' group and others have previously shown that ex vivo expansion and gene engineering can overcome CB-derived NK cells' functional immaturity and poor cytolytic activity, including in the presence of exogenous TGF-β.  However, a direct comparison of the effects of TGF-β-mediated immune suppression on ex vivo-expanded CB- versus PB-derived NK cell therapy products has not previously been performed. Here the authors show that PB- and CB-derived NK cells have distinctive gene signatures that can be overcome by ex vivo expansion. Additionally, exposure to exogenous TGF-β results in an upregulation of inhibitory receptors on NK cells, a novel immunosuppressive mechanism not previously described. Finally, the authors provide functional and genetic evidence that both PB- and CB-derived NK cells are equivalently susceptible to TGF-β-mediated immune suppression. The authors believe these results provide important mechanistic insights to consider when using ex vivo-expanded, TGF-β-resistant PB- or CB-derived NK cells as novel immunotherapy agents for cancer.

CAR T-cell Therapy in Highly-Aggressive B-Cell Lymphoma: Emerging Biological and Clinical Insights

Recently, significant progress has been made in identifying novel therapies, beyond conventional immunochemotherapy strategies, with efficacy in B-cell lymphomas. One such approach involves targeting the CD19 antigen on B-cells with autologous-derived chimeric antigen receptor (CAR) cells. This strategy is highly effective in patients with relapsed and refractory diffuse large B-cell lymphoma (DLBCL) as evidenced by recent regulatory approvals. Recent reports suggest that this is an effective strategy for high-grade B-cell. The biological underpinnings of these entities and how they overlap with each other and DLBCL continue to be areas of intense investigation. Therefore, as more experience with CAR T-cell approaches is examined, it is interesting to consider how both tumor-cell specific and microenvironment factors that define these highly aggressive subsets influence susceptibility to this approach.

Advances in CAR-T Cell Genetic Engineering Strategies to Overcome Hurdles in Solid Tumors Treatment

During this last decade, adoptive transfer of T lymphocytes genetically modified to express chimeric antigen receptors (CARs) emerged as a valuable therapeutic strategy in hematological cancers. However, this immunotherapy has demonstrated limited efficacy in solid tumors. The main obstacle encountered by CAR-T cells in solid malignancies is the immunosuppressive tumor microenvironment (TME). The TME impedes tumor trafficking and penetration of T lymphocytes and installs an immunosuppressive milieu by producing suppressive soluble factors and by overexpressing negative immune checkpoints. In order to overcome these hurdles, new CAR-T cells engineering strategies were designed, to potentiate tumor recognition and infiltration and anti-cancer activity in the hostile TME. In this review, we provide an overview of the major mechanisms used by tumor cells to evade immune defenses and we critically expose the most optimistic engineering strategies to make CAR-T cell therapy a solid option for solid tumors.

The Race of CAR Therapies: CAR-NK Cells for Fighting B-Cell Hematological Cancers

Simple Summary

Over the last few years, CAR-T cells have arisen as one of the most promising immunotherapies against relapsed or refractory hematological cancers. Despite their good results in clinical trials, there are some limitations to overcome, such as undesirable side-effects or the restraints of an autologous treatment. Therefore, CAR-NK cells have emerged as a good alternative for these kinds of treatments. This review discusses the advantages of CAR-NK cells compared to CAR-T cells, as well as the different sources and strategies in order to obtain these CAR-NK cells.

Abstract

Acute lymphoblastic leukemia (ALL) and Chronic lymphocytic leukemia (CLL) are the most common leukemias in children and elderly people, respectively. Standard therapies, such as chemotherapy, are only effective in 40% of ALL adult patients with a five-year survival rate and therefore new alternatives need to be used, such as immunotherapy targeting specific receptors of malignant cells. Among all the options, CAR (Chimeric antigen receptor)-based therapy has arisen as a new opportunity for refractory or relapsed hematological cancer patients. CARs were designed to be used along with T lymphocytes, creating CAR-T cells, but they are presenting such encouraging results that they are already in use as drugs. Nonetheless, their side-effects and the fact that it is not possible to infuse an allogenic CAR-T product without causing graft-versus-host-disease, have meant using a different cell source to solve these problems, such as Natural Killer (NK) cells. Although CAR-based treatment is a high-speed race led by CAR-T cells, CAR-NK cells are slowly (but surely) consolidating their position; their demonstrated efficacy and the lack of undesirable side-effects is opening a new door for CAR-based treatments. CAR-NKs are now in the field to stay.