Ex vivo activation of CD56(+) immune cells that eradicate neuroblastoma

CAR NK Cell Therapy for the Treatment of Metastatic Melanoma: Potential & Prospects

Melanoma is among the most lethal forms of cancer, accounting for 80% of deaths despite comprising just 5% of skin cancer cases. Treatment options remain limited due to the genetic and epigenetic mechanisms associated with melanoma heterogeneity that underlie the rapid development of secondary drug resistance. For this reason, the development of novel treatments remains paramount to the improvement of patient outcomes. Although the advent of chimeric antigen receptor-expressing T (CAR-T) cell immunotherapies has led to many clinical successes for hematological malignancies, these treatments are limited in their utility by their immune-induced side effects and a high risk of systemic toxicities. CAR natural killer (CAR-NK) cell immunotherapies are a particularly promising alternative to CAR-T cell immunotherapies, as they offer a more favorable safety profile and have the capacity for fine-tuned cytotoxic activity. In this review, the discussion of the prospects and potential of CAR-NK cell immunotherapies touches upon the clinical contexts of melanoma, the immunobiology of NK cells, the immunosuppressive barriers preventing endogenous immune cells from eliminating tumors, and the structure and design of chimeric antigen receptors, then finishes with a series of proposed design innovations that could improve the efficacy CAR-NK cell immunotherapies in future studies.

Lymphocyte expansion in bioreactors: upgrading adoptive cell therapy

Bioreactors are essential tools for the development of efficient and high-quality cell therapy products. However, their application is far from full potential, holding several challenges when reconciling the complex biology of the cells to be expanded with the need for a manufacturing process that is able to control cell growth and functionality towards therapy affordability and opportunity. In this review, we discuss and compare current bioreactor technologies by performing a systematic analysis of the published data on automated lymphocyte expansion for adoptive cell therapy. We propose a set of requirements for bioreactor design and identify trends on the applicability of these technologies, highlighting the specific challenges and major advancements for each one of the current approaches of expansion along with the opportunities that lie in process intensification. We conclude on the necessity to develop targeted solutions specially tailored for the specific stimulation, supplementation and micro-environmental needs of lymphocytes’ cultures, and the benefit of applying knowledge-based tools for process control and predictability.

Nanoformulation of CCL21 greatly increases its effectiveness as an immunotherapy for neuroblastoma

Neuroblastoma is the most commonly diagnosed extracranial solid tumor in children. The patients with aggressive metastatic disease or refractory/relapsed neuroblastoma currently face a dismally low chance of survival. Thus, there is a great need for more effective therapies for this illness. In previous studies, we, as well as others, showed that the immune cell chemoattractant C-C motif chemokine ligand 21 (CCL21) is effective as an intratumoral therapy able to slow the growth of cancers. In this current study, we developed and tested an injectable, slow-release, uniform, and optimally loaded alginate nanoformulation of CCL21 as a means to provide prolonged intratumoral treatment. The alginate-nanoformulated CCL21, when injected intratumorally into mice bearing neuroblastoma lesions, significantly prolonged survival and decreased the tumor growth rate compared to CCL21 alone, empty nanoparticles, or buffer. Notably, we also observed complete tumor clearance and subsequent full protection against tumor rechallenge in 33% of nanoformulated CCL21-treated mice. Greater intratumoral presence of nanoformulated CCL21, compared to free CCL21, at days 1 and 2 after treatment ended was confirmed through fluorescent labeling and tracking. Nanoformulated CCL21-treated tumors exhibited a general pattern of prolonged increases in anti-tumor cytokines and relatively lower levels of pro-tumor cytokines in comparison to tumors treated with CCL21 alone or buffer only. Thus, this novel nanoformulation of CCL21 is an effective treatment for neuroblastoma, and may have potential for the delivery of CCL21 to other types of solid tumors in the future and as a slow-release delivery modality for other immunotherapies.

NK cells to cure cancer

Natural Killer (NK) cells are innate lymphocytes able to mediate immune-surveillance and clearance of viral infected and tumor-transformed cells. Growing experimental and clinical evidence highlighted a dual role of NK cells either in the control of cancer development/progression or in promoting the onset of immune-suppressant tumor microenvironments. Indeed, several mechanisms of NK cell-mediated tumor escape have been described and these includes cancer-induced aberrant expression of activating and inhibitory receptors (i.e. NK cell immune checkpoints), impairments of NK cell migration to tumor sites and altered NK cell effector-functions. These phenomena highly contribute to tumor progression and metastasis formation. In this review, we discuss the latest insights on those NK cell receptors and related molecules that are currently being implemented in clinics either as possible prognostic factors or therapeutic targets to unleash NK cell anti-tumor effector-functions in vivo. Moreover, we address here the major recent advances in regard to the genetic modification and ex vivo expansion of anti-tumor specific NK cells used in innovative adoptive cellular transfer approaches.

Dynamic suspension culture improves ex vivo expansion of cytokine-induced killer cells by upregulating cell activation and glucose consumption rate

Ex vivo expansion is an effective strategy to acquire cytokine-induced killer (CIK) cells needed for clinical trials. In this work, the effects of dynamic suspension culture, which was carried out by shake flasks on a shaker, on CIK cells were investigated by the analysis of expansion characteristics and physiological functions, with the objective to optimize the culture conditions for ex vivo expansion of CIK cells. The results showed that the expansion folds of total cells in dynamic cultures reached 69.36 ± 30.36 folds on day 14, which were significantly higher than those in static cultures (9.24 ± 1.12 folds, P < 0.05), however, the proportions of CD3⁺ cells and CD3⁺CD56⁺ cells in both cultures were similar, leading to much higher expansion of CD3⁺ cells and CD3⁺CD56⁺ cells in dynamic cultures. Additionally, expanded CIK cells in two cultures possessed comparable physiological functions. Notably, significantly higher percentages of CD25⁺ cells and CD69⁺ cells were found in dynamic cultures (P <  0.05). Besides, much higher glucose consumption rate of cells (P <  0.05) but similar Y_Lac/gluc were observed in dynamic cultures. Further, cells in dynamic cultures had better glucose utilization efficiency. Together, these results suggested that dynamic cultures improved cell activation, then accelerated glucose consumption rate, which enhanced cell expansion and promoted glucose utilization efficiency of cells.

Interleukin 8 (CXCL8)-CXC chemokine receptor 2 (CXCR2) axis contributes to MiR-4437-associated recruitment of granulocytes and natural killer cells in ischemic stroke

Granulocytes and natural killer (NK) cells have been linked to brain injury in ischemic stroke. However, their recruitment from peripheral leucocytes in stroke patients is not well understood. Here, the expression of the interleukin 8 (CXCL8) in plasma, and CXC chemokine receptor 2 (CXCR2) in peripheral leucocytes of patients with ischemic stroke were evaluated. Based on the results, CXCR2 expression positively correlated with granulocytes and NK cells, which were in turn attracted by CXCL8. The results also indicated that CXCR2 was a direct target of microRNA (miR)-4437, a negative regulator of CXCR2, which was downregulated in peripheral leucocytes from patients with ischemic stroke. Furthermore, serum CXCL8 levels were associated with the infarct volume and functional outcomes in patients with ischemic stroke. The results of the receiver operating characteristic curve analysis with an optimal cut-off value of 34 pg/mL indicated serum CXCL8 levels could be a prognostic indicator for ischemic stroke. In conclusion, these data highlighted the involvement of the CXCL8-CXCR2 chemotactic axis in the recruitment of granulocytes and NK cells in ischemic stroke. Furthermore, miR-4437 was suggested as a novel target for treating ischemic stroke, while the serum CXCL8 level could be a prognostic factor for ischemic stroke.

Influence of Irradiated Peripheral Blood Mononuclear Cells on Both Ex Vivo Proliferation of Human Natural Killer Cells and Change in Cellular Property

Clinical studies with adoptive immunotherapy using allogeneic natural killer (NK) cells showed feasibility, but also limitation regarding the transfused absolute cell numbers. First promising results with peripheral blood mononuclear cells (PBMCs) as feeder cells to improve the final cell number need further optimization and investigation of the unknown controlling mechanism in the cross-talk to NK cells. We investigated the influence of irradiated autologous PBMCs to boost NK cell proliferation in the presence of OKT3 and IL-2. Our findings demonstrate a requirement for receptor-ligand interactions between feeders and NK cells to produce soluble factors that can sustain NK cell proliferation. Thus, both physical contact between feeder and NK cells, and soluble factors produced in consequence, are required to fully enhance NK cell ex vivo proliferation. This occurred with an indispensable role of the cross-talk between T cells, monocytes, and NK cells, while B cells had no further influence in supporting NK cell proliferation under these co-culture conditions. Moreover, gene expression analysis of highly proliferating and non-proliferating NK cells revealed important phenotypic changes on 5-day cultured NK cells. Actively proliferating NK cells have reduced Siglec-7 and -9 expression compared with non-proliferating and resting NK cells (day 0), independently of the presence of feeder cells. Interestingly, proliferating NK cells cultured with feeder cells contained increased frequencies of cells expressing RANKL, B7-H3, and HLA class II molecules, particularly HLA-DR, compared with resting NK cells or expanded with IL-2 only. A subset of HLA-DR expressing NK cells, co-expressing RANKL, and B7-H3 corresponded to the most proliferative population under the established co-culture conditions. Our results highlight the importance of the crosstalk between T cells, monocytes, and NK cells in autologous feeder cell-based ex vivo NK cell expansion protocols, and reveal the appearance of a highly proliferative subpopulation of NK cells (HLA-DR⁺RANKL⁺B7-H3⁺) with promising characteristics to extend the therapeutic potential of NK cells.

Natural killer cells as a promising tool to tackle cancer-A review of sources, methodologies, and potentials

Immune cell-based therapies are emerging as a promising tool to tackle malignancies, both solid tumors and selected hematological tumors. Vast experiences in literature have documented their safety and added survival benefits when such cell-based therapies are combined with the existing treatment options. Numerous methodologies of processing and in vitro expansion protocols of immune cells, such as the dendritic cells, natural killer (NK) cells, NKT cells, αβ T cells, so-called activated T lymphocytes, γδ T cells, cytotoxic T lymphocytes, and lymphokine-activated killer cells, have been reported for use in cell-based therapies. Among this handful of immune cells of significance, the NK cells stand apart from the rest for not only their direct cytotoxic ability against cancer cells but also their added advantage, which includes their capability of (i) action through both innate and adaptive immune mechanism, (ii) tackling viruses too, giving benefits in conditions where viral infections culminate in cancer, and (iii) destroying cancer stem cells, thereby preventing resistance to chemotherapy and radiotherapy. This review thoroughly analyses the sources of such NK cells, methods for expansion, and the future potentials of taking the in vitro expanded allogeneic NK cells with good cytotoxic ability as a drug for treating cancer and/or viral infection and even as a prophylactic tool for prevention of cancer after initial remission.

Shaping of Natural Killer Cell Antitumor Activity by Ex Vivo Cultivation

Natural killer (NK) cells are a promising tool for the use in adoptive immunotherapy, since they efficiently recognize and kill tumor cells. In this context, ex vivo cultivation is an attractive option to increase NK cells in numbers and to improve their antitumor potential prior to clinical applications. Consequently, various strategies to generate NK cells for adoptive immunotherapy have been developed. Here, we give an overview of different NK cell cultivation approaches and their impact on shaping the NK cell antitumor activity. So far, the cytokines interleukin (IL)-2, IL-12, IL-15, IL-18, and IL-21 are used to culture and expand NK cells. The selection of the respective cytokine combination is an important factor that directly affects NK cell maturation, proliferation, survival, distribution of NK cell subpopulations, activation, and function in terms of cytokine production and cytotoxic potential. Importantly, cytokines can upregulate the expression of certain activating receptors on NK cells, thereby increasing their responsiveness against tumor cells that express the corresponding ligands. Apart from using cytokines, cocultivation with autologous accessory non-NK cells or addition of growth-inactivated feeder cells are approaches for NK cell cultivation with pronounced effects on NK cell activation and expansion. Furthermore, ex vivo cultivation was reported to prime NK cells for the killing of tumor cells that were previously resistant to NK cell attack. In general, NK cells become frequently dysfunctional in cancer patients, for instance, by downregulation of NK cell activating receptors, disabling them in their antitumor response. In such scenario, ex vivo cultivation can be helpful to arm NK cells with enhanced antitumor properties to overcome immunosuppression. In this review, we summarize the current knowledge on NK cell modulation by different ex vivo cultivation strategies focused on increasing NK cytotoxicity for clinical application in malignant diseases. Moreover, we critically discuss the technical and regulatory aspects and challenges underlying NK cell based therapeutic approaches in the clinics.

Involvement of IL-10 and TGF-β in HLA-E-mediated neuroblastoma migration and invasion

Human leukocyte antigen (HLA)-E is highly expressed in a variety of tumors and, in addition to immune escape, may promote tumor growth via other mechanisms. However, the role of HLA-E in neuroblastoma (NB) migration and invasion is unknown. In the present study, HLA-E expression in human NB tumors was measured by immunohistochemistry. The effect of HLA-E on NB cell migration and invasion was studied in vitro and in vivo, as well as the effect of HLA-E on natural killer (NK)-cell cytotoxicity. HLA-E was expressed in 70.2% of the NB tumor tissues examined. HLA-E expression by NB cells inhibited NK-cell cytotoxicity and induced the release of interleukin (IL)-10 and transforming growth factor (TGF)-β1. HLA-E and the released cytokines enhanced the ability of NB cells migration and invasion. NK cell infusion did not inhibit the growth of NB cells with high HLA-E expression but instead increased the number of metastatic cells in the bone marrow. Taken together, the results indicate that IL-10 and TGF-β are involved in HLA-E-mediated NB migration and invasion. Thus, HLA-E may be a new treatment target in NB.

KIR-HLA profiling shows presence of higher frequencies of strong inhibitory KIR-ligands among prognostically poor risk AML patients

The expression and interaction between killer cell immunoglobulin-like receptors (KIRs) and HLA are known to be associated with pathogenesis of diseases, including hematological malignancies. Presence of B haplotype KIR in donors is associated with a lower relapse risk for acute myeloid leukemia (AML) after hematopoietic stem cell transplants (HSCT). However, the association of KIR and HLA repertoire with disease development and other clinical features is not well studied for AML. In this study, 206 Chinese patients with AML were analyzed for their FAB subtypes, risk groups, and chemo-responsiveness to assess possible association with their KIR and HLA profile. The results revealed that a B-content score of 2 was significantly more prevalent in AML patients when compared to normal controls. Notably, there is also a differential frequency in the distribution of B haplotype KIR across distinct FAB subtypes, where the M3 subtype had significantly lower frequencies of B haplotype KIR compared to the M5 subtype (p < 0.05). In addition, the stronger inhibitory KIR ligands HLA-C2 and HLA-Bw4-80I were present in significantly higher frequencies in the prognostically "poor" risk group compared to those with "favourable" risk (p < 0.01). Taken together, these associations with clinical features of AML suggest a role of the KIR-HLA repertoire in the development and biological behavior of AML.

Natural killer cell therapy in children with relapsed leukemia

BACKGROUND

Novel therapies are needed for children with relapsed or refractory leukemia. We therefore tested the safety and feasibility of haploidentical natural killer cell therapy in this patient population.

PROCEDURE

Twenty-nine children who had relapsed or refractory leukemia were treated with chemotherapy followed by the infusion of haploidentical NK cells. Cohort 1 included 14 children who had not undergone prior allogeneic hematopoietic cell transplantation (HCT), whereas Cohort 2 included 15 children with leukemia that had relapsed after HCT.

RESULTS

Twenty-six (90%) NK donors were KIR mismatched (14 with one KIR and 12 with 2 KIRs). The peak NK chimerism levels were >10% donor in 87% of the evaluable recipients. In Cohort 1, 10 had responsive disease and 12 proceeded to HCT thereafter. Currently, 5 (36%) are alive without leukemia. In Cohort 2, 10 had responsive disease after NK therapy and successfully proceeded to second HCT. At present, 4 (27%) are alive and leukemia-free. The NK cell infusions and the IL-2 injections were well-tolerated.

CONCLUSIONS

NK cell therapy is safe, feasible, and should be further investigated in patients with chemotherapy-resistant leukemia.

NK cell-based immunotherapies in Pediatric Oncology

The past decade has seen several anticancer immunotherapeutic strategies transition from "promising preclinical models" to treatments with proven clinical activity or benefit. In 2013, the journal Science selected the field of Cancer Immunotherapy as the overall number-1 breakthrough for the year in all of scientific research. In the setting of cancer immunotherapy for adult malignancies, many of these immunotherapy strategies have relied on the cancer patient's endogenous antitumor T-cell response. Although much promising research in pediatric oncology is similarly focused on T-cell reactivity, several pediatric malignancies themselves, or the chemo-radiotherapy used to achieve initial responses, can be associated with profound immune suppression, particularly of the T-cell system. A separate component of the immune system, also able to mediate antitumor effects and less suppressed by conventional cancer treatment, is the NK-cell system. In recent years, several distinct immunotherapeutic approaches that rely on the activity of NK cells have moved from preclinical development into clinical testing, and some have shown clear antitumor benefit. This review provides an overview of NK cell-based immunotherapy efforts that are directed toward childhood malignancies, with an emphasis on protocols that are already in clinical testing.

Infusions of allogeneic natural killer cells as cancer therapy

Natural killer (NK) cells are normal white blood cells capable of killing malignant cells without prior sensitization. Allogeneic NK cell infusions are attractive for cancer therapy because of non-cross-resistant mechanisms of action and minimal overlapping toxicities with standard cancer treatments. Although NK therapy is promising, many obstacles will need to be overcome, including insufficient cell numbers, failure of homing to tumor sites, effector dysfunction, exhaustion, and tumor cell evasion. Capitalizing on the wealth of knowledge generated by recent NK cell biology studies and the advancements in biotechnology, substantial progress has been made recently in improving therapeutic efficiency and reducing side effects. A multipronged strategy is essential, including immunogenetic-based donor selection, refined NK cell bioprocessing, and novel augmentation techniques, to improve NK function and to reduce tumor resistance. Although data from clinical trials are currently limited primarily to hematologic malignancies, broader applications to a wide spectrum of adult and pediatric cancers are under way. The unique properties of human NK cells open up a new arena of novel cell-based immunotherapy against cancers that are resistant to contemporary therapies.

Enhanced cytotoxic function of natural killer and CD3+CD56+ cells in cord blood after culture

Rate of immune reconstitution directly correlates with the number of hematopoietic stem cells infused and is particularly delayed in patients undergoing cord blood (CB) transplantation (CBT). Methods to increase the number of CB natural killer (NK) cells have the potential to improve immune reconstitution after CBT. NK cells are the first lymphocyte population to recover after hematopoietic stem cells transplantation and are central to preventing early relapse and infection. CB NK cells are low in number and are known to be incomplete in maturation and require activation for effective function. Here, we report a clinically relevant ex vivo expansion method that increases the number of activated CB NK cells. We report a multilog increase in NK cell number when CB mononuclear cells are cocultured with IL-2 and IL-15. Furthermore, NK cells expressing activating receptors and adhesion molecules responsible for cytotoxicity increased throughout culture, whereas inhibitory receptor expression remained low. Additionally, cytotoxic function against various malignancies was significantly enhanced in cultured NK cells but not CD3(+)CD56(+) cells. These data suggest that ex vivo expansion and activation of CB NK cells is a clinically feasible and relevant approach to prevent early infection and relapse after CBT.

Natural killer cells and neuroblastoma: tumor recognition, escape mechanisms, and possible novel immunotherapeutic approaches

Neuroblastoma (NB) is the most common extra-cranial solid tumor of childhood and arises from developing sympathetic nervous system. Most primary tumors localize in the abdomen, the adrenal gland, or lumbar sympathetic ganglia. Amplification in tumor cells of MYCN, the major oncogenic driver, patients' age over 18 months, and the presence at diagnosis of a metastatic disease (stage IV, M) identify NB at high risk of treatment failure. Conventional therapies did not significantly improve the overall survival of these patients. Moreover, the limited landscape of somatic mutations detected in NB is hampering the development of novel pharmacological approaches. Major efforts aim to identify novel NB-associated surface molecules that activate immune responses and/or direct drugs to tumor cells and tumor-associated vessels. PVR (Poliovirus Receptor) and B7-H3 are promising targets, since they are expressed by most high-risk NB, are upregulated in tumor vasculature and are essential for tumor survival/invasiveness. PVR is a ligand of DNAM-1 activating receptor that triggers the cytolytic activity of natural killer (NK) cells against NB. In animal models, targeting of PVR with an attenuated oncolytic poliovirus induced tumor regression and elimination. Also B7-H3 was successfully targeted in preclinical studies and is now being tested in phase I/II clinical trials. B7-H3 down-regulates NK cytotoxicity, providing NB with a mechanism of escape from immune response. The immunosuppressive potential of NB can be enhanced by the release of soluble factors that impair NK cell function and/or recruitment. Among these, TGF-β1 modulates the cytotoxicity receptors and the chemokine receptor repertoire of NK cells. Here, we summarize the current knowledge on the main cell surface molecules and soluble mediators that modulate the function of NK cells in NB, considering the pros and cons that must be taken into account in the design of novel NK cell-based immunotherapeutic approaches.

Modulation of NKG2D ligand expression and metastasis in tumors by spironolactone via RXRγ activation

The diuretic drug spironolactone up-regulates NKG2D ligand expression in colon cancer cells via activation of the ATM–Chk2–mediated checkpoint pathway to enhance the antitumor function of NK cells.

Tumor metastasis and lack of NKG2D ligand (NKG2DL) expression are associated with poor prognosis in patients with colon cancer. Here, we found that spironolactone (SPIR), an FDA-approved diuretic drug with a long-term safety profile, can up-regulate NKG2DL expression in multiple colon cancer cell lines by activating the ATM–Chk2-mediated checkpoint pathway, which in turn enhances tumor elimination by natural killer cells. SPIR can also up-regulate the expression of metastasis-suppressor genes TIMP2 and TIMP3, thereby reducing tumor cell invasiveness. Although SPIR is an aldosterone antagonist, its antitumor effects are independent of the mineralocorticoid receptor pathway. By screening the human nuclear hormone receptor siRNA library, we identified retinoid X receptor γ (RXRγ) instead as being indispensable for the antitumor functions of SPIR. Collectively, our results strongly support the use of SPIR or other RXRγ agonists with minimal side effects for colon cancer prevention and therapy.