Interleukin (IL)-15 in combination with IL-2, fms-like tyrosine kinase-3 ligand and anti-CD3 significantly enhances umbilical cord blood natural killer (NK) cell and NK-cell subset expansion and NK function

Cord blood derived NK cells activated in counter with tumor cells

NK cells are initially known for their ability to kill tumor cells with no prior sensitization. Production of mature and long lasting NK cells from Umbilical Cord Blood (UCB) by using cytokines could be a promising method for immunotherapy. NK cells were generated from cord blood cells using IL2, IL7, and IL15 cytokines and measured expression of CD57 and NKp46 markers. Afterward, their capacity in the elimination of malignant cells (Reh cell line) was evaluated by assessment of interferon-γ (as cytokine production sign) and CD107-a expression (as cytotoxic function symptom) using flow cytometry. Our results showed efficient NKp46 + , and CD57 + NK cells generated on day 14. Also, expression of CD107-a and IFN-γ following co-culture with Reh cell lines significantly increased in comparison to the control. Taken together, we have reported one of the best culture conditions for the generation of CD57 + NK cells with on feeder cells and showed appropriate capacity in counter reh cell lines as a target.

Chimeric antigen receptor-engineered NK cells: new weapons of cancer immunotherapy with great potential

Chimeric antigen receptor (CAR)-engineered T (CAR-T) cells have obtained prominent achievement in the clinical immunotherapy of hematological malignant tumors, leading to a rapid development of cellular immunotherapy in cancer treatment. Scientists are also aware of the prospective advantages of CAR engineering in cellular immunotherapy. Due to various limitations such as the serious side effects of CAR-T therapy, researchers began to investigate other immune cells for CAR modification. Natural killer (NK) cells are critical innate immune cells with the characteristic of non-specifically recognizing target cells and with the potential to become "off-the-shelf" products. In recent years, many preclinical studies on CAR-engineered NK (CAR-NK) cells have shown their remarkable efficacy in cancer therapy and their superiority over autologous CAR-T cells. In this review, we summarize the generation, mechanisms of anti-tumor activity and unique advantages of CAR-NK cells, and then analyze some challenges and recent clinical trials about CAR-NK cells therapy. We believe that CAR-NK therapy is a promising prospect for cancer immunotherapy in the future.

IL-15 and IL15RA in Osteoarthritis: Association With Symptoms and Protease Production, but Not Structural Severity

Objective: Interleukin-15 (IL-15) is a pro-inflammatory cytokine that is increased in joint fluids of early-stage osteoarthritis (OA) patients, and has been associated with expression of proteases that can damage cartilage, and the development of neuropathic pain-like symptoms (NP) after nerve injury. The objective of this study was to further explore the role of IL-15 in the pathogenesis of OA cartilage degeneration and test genetic variation in the IL-15 receptor α gene (IL15RA) for an association with OA with radiographic severity and symptoms. Methods: Cartilage samples from donors (n = 10) were analyzed for expression of the IL15 receptor α-chain using immunohistochemistry, and for responses to IL-15 in vitro using explant cultures. Data from two independent Nottinghamshire-based studies (n = 795 and n = 613) were used to test genetic variants in the IL15RA gene (rs2228059 and rs7097780) for an association with radiographic severity, symptomatic vs. asymptomatic OA and NP. Results: IL-15Rα was expressed in chondrocytes from cartilage obtained from normal and degenerative knees. IL-15 significantly increased the release of matrix metalloproteinase-1 and -3 (MMP-1 and -3), but did not affect loss of proteoglycan from the articular matrix. Genetic variants in the IL15RA gene are associated with risk of symptomatic vs. asymptomatic OA (rs7097780 OR = 1.48 95% 1.10-1.98 p < 0.01) and with the risk of NP post-total joint replacement (rs2228059 OR = 0.76 95% 0.63-0.92 p < 0.01) but not with radiographic severity. Conclusions: In two different cohorts of patients, we show an association between genetic variation at the IL15 receptor and pain. Although ex vivo cartilage explants could respond to IL-15 with increased protease production, we found no effect of IL-15 on cartilage matrix loss and no association between IL15RA variants and radiographic severity. Together, these results suggest that IL-15 signaling may be a target for pain, but may not impact structural progression, in OA.

Evaluation of serum-free media formulations in feeder cell-stimulated expansion of natural killer cells

BACKGROUND

Optimal expansion of therapeutic natural killer (NK) cell products has required media supplementation with human or fetal bovine serum, which raises safety and regulatory concerns for clinical manufacturing. Serum-free media (SFM) have been optimized for T-cell expansion, but few SFM systems have been developed for NK cells. Here, we compare six commercial clinical-grade SFM with our standard fetal bovine serum-containing medium for their ability to support NK cell expansion and function.

METHODS

Human peripheral blood NK cells were expanded in selected media by recursive weekly stimulation with K562-based feeder cells expressing membrane-bound interleukin-21 and CD137L. Expansion was the primary readout, and the best-performing SFM was then compared with standard medium for cytotoxicity, phenotype, degranulation and cytokine secretion. Multiple lots were compared for consistency, and media was analyzed throughout for nutrient consumption and metabolic byproducts.

RESULTS

TexMACS, OpTmizer, SCGM, ABS-001 and StemXVivo demonstrated equal or inferior NK cell expansion kinetics compared with standard medium, but expansion was markedly superior with AIM V + 5% Immune Cell Serum Replacement (ICSR; mean 5448 vs. 2621-fold expansion in 14 days). Surprisingly, NK cells expanded in AIM V + ICSR also showed increased cytotoxicity, tumor necrosis factor α secretion and DNAM-1, NKG2D, NKp30, FasL, granzyme B and perforin expression. Lot-to-lot variability was minimal. Glucose and glutamine consumption were inversely related to lactate and ammonia production.

DISCUSSION

The AIM V + ICSR SFM system supports excellent ex vivo expansion of clinical-grade NK cells with the phenotype and function needed for adoptive immunotherapy.

Cord blood stem cell derived CD16+ NK cells eradicated acute lymphoblastic leukemia cells using with anti-CD47 antibody

Acute lymphoblastic leukemia (ALL) is an aggressive cancer in children and adults which possess higher CD47 expression than normal cells. ALL chemotherapy has a lot of side effects and in most cases is ineffective. However arrival of Natural killer (NK) cell immunotherapy raised hopes for successful treatment of cancers, tailoring NK cells to meet clinical requirements is still under investigation. Of note, CD16⁺ (FCγIIIa) NK cells eliminate tumor cells with antibody dependent cell cytotoxicity (ADCC) mechanism. Therefore, we evaluated ADCC effect of cord blood stem cell derived CD16⁺ NK cells with using anti CD47 blocking antibody. CD16⁺ NK cells generated efficiently from CD34 positive cord blood cells in vitro using IL-2, IL-15 and IL-21 cytokines, although it was not dose dependent. CD16⁺ cells derived from CD34⁺ cells in day 14 of culture efficiently increased apoptosis in ALL cells, produced INFγ and increased CD107-a expression when used anti CD47 antibody (increased around 30-40%). Interestingly, CD16⁺ NK cell cytotoxicity slightly increased in combination with macrophages against ALL cells (around 10%). Taken together, our findings induced this hope that cord blood stem cell derived CD16⁺ NK cells exploit antitumor immune response in cancer therapy with using anti-CD47 antibody.

Umbilical Cord Blood-Derived Natural Killer Cells Combined with Bevacizumab for Colorectal Cancer Treatment

Colorectal cancer (CRC) is among the cancers with the highest incidence globally, and it currently ranks as the fourth leading cause of cancer-related deaths worldwide. Novel strategies for the treatment of advanced CRC are urgently needed, and adoptive transfer of allogeneic natural killer (NK) cells represents an attractive option. In this study, we successfully expanded NK cells from umbilical cord blood (UCB) with membrane-bound interleukin (IL)-21, termed eUCB-NK cells. eUCB-NK cells efficiently lysed CRC cell lines in vitro and secreted significantly higher levels of interferon-γ, tumor necrosis factor-α, granulocyte-macrophage colony stimulating factor, and chemokine ligand 3 compared with IL-2-stimulated NK cells. Adoptive transfer of these NK cells significantly inhibited the growth of HT29 xenografts, whereas LoVo tumors were not effectively controlled with eUCB-NK cells. Higher numbers of NK cells inside HT29 tumors, not seen in LoVo tumors, might contribute to the differences in response to eUCB-NK cells. Bevacizumab increased extravasation of adoptively transferred NK cells into LoVo tumors and improved the therapeutic activity of eUCB-NK cells. These results justify clinical translation of UCB-derived NK cell-based therapeutics, used alone or in combination with bevacizumab, as a novel treatment option for patients with CRC.

NK cell therapy after hematopoietic stem cell transplantation: can we improve anti-tumor effect?

After decades since the discovery of natural killer (NK) cells as potential effector cells fighting malignantly transformed and virally infected cells, little progress has been made in their clinical application. This yet unrealized therapeutic effect is presumably, at least in part, due to low numbers of functional NK cells that could be obtained from the peripheral blood relative to tumor burden. Our group hypothesized that a relatively small NK cell number to targeted malignant cells is the cause of a lack of clinical effect. We pursued obtaining large numbers of NK cells via ex vivo expansion using feeder cells that express membrane-bound IL-21. Early clinical studies demonstrate safety of administration of ex vivo expanded NK cells after transplantation using this method and suggest a therapeutic benefit in terms on decreasing relapse rate and possible control of viral infections post-transplant can be achieved. Successful application of NK cells after hematopoietic stem cell transplantation opens the possibility to effectively enhance the anti-tumor effect and decrease relapse rate post-transplant. Moreover, high doses of NK cells could prove more efficacious in enhancing anti-tumor effects, not only in hematological malignancies, with our without transplantation, but also in solid tumor oncology.

Umbilical Cord Blood Natural Killer Cells, Their Characteristics, and Potential Clinical Applications

Natural killer (NK) cells are lymphocytes of the innate immune system able to kill different targets such as cancer cells and virally infected cells without prior activation making then attractive candidates for cancer immunotherapy. Umbilical cord blood (UCB) has become a source of hematopoietic stem cells for transplantation but as we gain a better understanding of the characteristics of each immune cell that UCB contains, we will also be able to develop new cell therapies for cancer. In this review, we present what is currently known of the phenotype and functions of UCB NK cells and how these cells could be used in the future for cancer immunotherapy.

Natural killer cells in malignant hematology: A primer for the non-immunologist

Natural killer cells were first described over 40years ago, but the last 15years has shown tremendous progress in our understanding of their biology and our ability to manipulate them for clinical therapeutic effect. Despite the increased understanding by clinicians and scientists investigating these cells, their biology remains a confusing subject for many because of the wide array of receptors, complex interactions, multiple models of predicting function, and contradictory data in the literature. While they are microscopically indistinguishable from T cells and share many of the same effector functions, their mechanisms of target recognition are completely distinct from yet complimentary to T cells. In this review we provide a basic understanding of NK cell biology and HLA recognition as compared and contrasted to T cells using a metaphor of border patrol and passports. We conclude with a summary of the evidence for NK cell effects in hematologic malignancies and describe new advances in NK cell immunotherapy aimed at improving these effects.

Expanded and armed natural killer cells for cancer treatment

The capacity of natural killer (NK) cells to recognize and kill transformed cells suggests that their infusion could be used to treat cancer. It is difficult to obtain large numbers of NK cells ex vivo by exposure to cytokines alone but the addition of stimulatory cells to the cultures can induce NK cell proliferation and long-term expansion. Some of these methods have been validated for clinical-grade application and support clinical trials testing feasibility and safety of NK cell administration. Early data indicate that ex vivo expansion of NK cells from healthy donors or from patients with cancer is robust, allowing multiple infusions from a single apheresis. NK cells can transiently expand in vivo after infusion. Allogeneic NK cells are not direct effectors of graft-versus-host disease but this may occur if donor NK cells are infused after allogeneic hematopoietic stem cell transplant, which may activate T cell alloreactivity. NK cells can be directed with antibodies, or engineered using either transient modification by electroporation of mRNA or prolonged gene expression by viral transduction. Thus, expanded NK cells can be armed with activating receptors that enhance their natural anti-tumor capacity or with chimeric antigen receptors that can redirect them towards specific tumor targets. They can also be induced to express cytokines that promote their autonomous growth, further supporting their in vivo expansion. With the implementation of these approaches, expanded and armed NK cells should ultimately become a powerful component of immunotherapy of cancer.

A novel method to expand large numbers of CD56(+) natural killer cells from a minute fraction of selectively accessed cryopreserved cord blood for immunotherapy after transplantation

BACKGROUND AIMS

Umbilical cord blood transplantation (UCBT) is increasingly used to treat acute leukemias. UCB units are thawed and infused in their entirety at transplant, precluding later use as immunotherapy to prevent or treat leukemia relapse.

METHODS

We developed a device that selectively thaws only 1 mL of the UCB unit, leaving the remaining UCB unit cryopreserved for subsequent transplantation. We also show that large numbers of CD56(+) natural killer (NK) cells can be expanded from these 1-mL fractions of selectively accessed UCB. Immunomagnetic depletion of CD3(+) cells of the 1-mL fraction was performed, and the cells were subsequently stimulated with irradiated Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCLs) and set to culture in media containing interleukin (IL)-2.

RESULTS

When a 1:20 ratio of total nucleated cells to EBV-LCL feeder cells was used, day-21 and day-35 NK cell cultures initiated from 1 mL of UCB contained a median of 430 × 10(6) (range: 44-4321 × 10(6)) and 6092 × 10(6) (range: 165-20947 × 10(6)) CD3(-)CD56(+) NK cells. These cells expressed high levels of CD161, LFA-1, CD69, NKG2D, NKp30, NKp44, NKp80 and NKp46. UCB-derived NK cells were highly cytotoxic against K562 leukemia cells, although cytotoxicity was slightly lower than in expanded PBMC-derived NK cells.

CONCLUSIONS

We have developed and optimized a strategy to selectively access a small fraction from cryopreserved UCB and show that large numbers of CD56(+) cells can be expanded from this selectively accessed fraction. This strategy presents a method to explore whether early adoptive transfer of NK cells expanded from the same UCB unit used for transplantation can prevent leukemic relapse and decrease graft-versus-host disease after UCBT.

Cellular engineering and therapy in combination with cord blood allografting in pediatric recipients

Cord blood (CB) transplantation is an alternate source of human hematopoietic progenitor cells for allogeneic stem cell transplantation in children and adolescents with both malignant and nonmalignant diseases. Current limitations included delay in hematopoietic reconstitution, increased incidence of primary graft failure and slow cellular immunoreconstitution. These limitations lead to a significant increase in primary graft failure, infectious complications and increased transplant-related mortality. There is a number of experimental approaches currently under investigation including cellular engineering to circumvent these limitations. In this review, we summarize the recent findings of utilizing ex vivo CB expansion with Notch1 ligand Delta 1, mesenchymal progenitor cells, the use of human placenta-derived stem cells and CB-derived natural killer cells. Early and preliminary results suggest some of these experimental cellular strategies may in part ameliorate the incidence of primary graft failure, delays in hematopoietic reconstitution and/or slowness in cellular immune reconstitution following unrelated CB transplantation.

Umbilical cord blood-derived cellular products for cancer immunotherapy

Although the vast majority of experience with umbilical cord blood (CB) centers on hematopoietic reconstitution, a recent surge in the knowledge of CB cell subpopulations as well as advances in ex vivo culture technology have expanded the potential of this rich resource. Because CB has the capacity to generate the entire hematopoietic system, we now have a new source for natural killer, dendritic and T cells for therapeutic use against malignancies. This Review will focus on cellular immunotherapies derived from CB. Expansion techniques, ongoing clinical trials and future directions for this new dimension of CB application are also discussed.

Differential activation of cord blood and peripheral blood natural killer cells by cytokines

BACKGROUND AIMS

Natural killer (NK) cells play important roles in the clearance of infection and transformed cells. Cord blood (CB) is currently used as a source of hematopoietic stem cells for transplantation and is a potential source of NK cells for immunotherapy. We previously showed that CB NK cells are immature and less cytotoxic as compared with peripheral blood (PB) NK cells. We aimed to identify which cytokines, among interleukin (IL)-2, IL-12, IL-15 and IL-18 and their combinations, could fully activate CB NK cells as compared with PB NK cells.

METHODS

We performed a comprehensive analysis of phenotype and functionality of cytokine-activated NK cells.

RESULTS

Our results show that the lower responsiveness of CB NK cells to IL-2 is associated with lower levels of expression of IL-2 receptors and decreased phosphorylation of STAT5 as compared with PB NK cells. Activation of CB NK cells with IL-15+18 led to the most robust proliferative response and higher interferon-γ and tumor necrosis factor-α secretion, whereas activation with IL-15+2 promoted enhanced cytotoxicity. PB NK cells responded significantly better to IL-2 than to CB NK cells but were also fully activated with other cytokine treatments including IL-15, IL-15+2 or IL-15+18. It was also possible to use cytokines to generate memory-like NK cells, with sustained ability to produce interferon-γ, from both CB and PB.

CONCLUSIONS

CB NK cells are fully functional on activation with IL-15+2 or IL-15+18 rather than IL-2 alone as observed for PB NK cells. These cytokines should be considered in the future to activate CB NK cells for therapeutic purposes.

Upregulation of NKG2D ligands in acute lymphoblastic leukemia and non-Hodgkin lymphoma cells by romidepsin and enhanced in vitro and in vivo natural killer cell cytotoxicity

BACKGROUND AIMS

There is a critical need to prevent and/or treat hematological relapse after allogeneic hematopoietic stem cell transplantation. The activating NKG2D receptor expressed on natural killer (NK) cells, when engaged by its corresponding ligands (MIC A/B), activates NK cells to become cytotoxic against malignant cells.

METHODS

We incubated acute lymphoblastic leukemia and non-Hodgkin lymphoma cells for 24 h with 10 ng/mL of romidepsin. Flow cytometry was performed to demonstrate changes in surface expression of NKG2D ligands MIC A/B. In vitro and in vivo cytotoxicity was measured by means of modified Europium assay, and non-obese diabetic/severe combined immunodeficiency mice were xenografted with RS 4:11 cells.

RESULTS

We demonstrated an approximately 50, 200, 1300 and 180-fold increase in the number of cells positive for the surface expression of MIC A/B in RS 4:11 (P < 0.001), REH (P < 0.001), Ramos (P < 0.001) and Jurkat cells (P < 0.001), respectively. We further demonstrated a significant increase in NK cell-mediated in vitro cytotoxicity against RS 4:11 (P < 0.004), Ramos (P < 0.05), Jurkat (P < 0.001) and REH cells (P < 0.01), respectively. Romidepsin-mediated NK cytotoxicity was blocked by pre-incubating NK cells with anti-NKG2D-Fc in RS 4:11 (P < 0.03) and Ramos cells (P < 0.01), respectively. Finally, non-obese diabetic/severe combined immunodeficiency mice xenografted with RS 4:11 cells had a significant increase in survival (P < 0.02) in mice treated with romidepsin and interleukin-2-activated NK cells compared with each of these other treatment groups.

CONCLUSIONS

Romidepsin significantly enhanced in vitro and in vivo NK cell cytotoxicity mediated in part by increased MIC A/B expression on malignant cells. This translational approach of the use of romidepsin and interleukin-2-activated NK cells should be considered in patients with relapsed/refractory leukemia or lymphoma.

Umbilical cord blood immunology: relevance to stem cell transplantation

Because of its easier accessibility and less severe graft-versus-host disease, umbilical cord blood (UCB) has been increasingly used as an alternative to bone marrow for hematopoietic stem cell transplantation. Naiveté of UCB lymphocytes, however, results in delayed immune reconstitution and infection-related mortality in transplant recipients. This review updates the phenotypic and functional deficiencies of various immune cell populations in UCB compared with their adult counterparts and discusses clinical implications and possible therapeutic strategies to improve the outcome of stem cell transplantation.

Comparison of the cytotoxic response against ovarian cancer by immune effector cells isolated and expanded from normal donors and ovarian cancer patients

BACKGROUND/AIMS

The aim of this study was to compare the cytotoxic response against ovarian cancer (OC) cells elicited by different immune effector cells in combination with the cytokines interleukin (IL)-2 and interferon (IFN) α-2b.

METHODS

OC cells were co-cultured with peripheral blood mononuclear cells (PBMC) from normal donors or OC patients and IL-2 or IFN α-2b alone or in combination, in order to determine the cytotoxicity. T cells were isolated from healthy donors to determine T cell cytotoxic activity. PBMC from healthy donors and OC patients were expanded in an IL-2/IL-7/IL-12 cocktail with and without anti-CD3 antibody, and the cytotoxic activity measured. Flow cytometry was performed on primary, selected and expanded cells to determine T, B, and natural killer- (NK) cell percentages.

RESULTS

Healthy donor PBMC elicited a significant cytotoxic response (59%) compared with OC patient PBMC (7%). T cells enriched from normal donors elicited a significant cytotoxic response (18%) compared with controls lacking effector cells (1.4%); however, the cytotoxicity observed was significantly less compared with unselected PBMC. Expanded effector cells consisted primarily of T cells (98%) and the fold-expansion was significantly higher in the presence of anti-CD3 (19- versus 132-fold). No significant difference in the expansion (either fold-expansion or cell type) was observed between OC patients and healthy donors. Expanded cells from both healthy donors and OC patients elicited a significant cytotoxic response in the presence of IL-2 (19% and 22%) compared with controls.

CONCLUSIONS

PBMC from OC patients do not elicit a significant cytotoxic response; however, ex vivo-expanded cells from OC patients are capable of cytotoxic killing similar to unexpanded T cells isolated from normal donors. These data provide the groundwork for further development of cellular therapy against OC.

Membrane-bound IL-21 promotes sustained ex vivo proliferation of human natural killer cells

NK cells have therapeutic potential for a wide variety of human malignancies. However, because NK cells expand poorly in vitro, have limited life spans in vivo, and represent a small fraction of peripheral white blood cells, obtaining sufficient cell numbers is the major obstacle for NK-cell immunotherapy. Genetically-engineered artificial antigen-presenting cells (aAPCs) expressing membrane-bound IL-15 (mbIL15) have been used to propagate clinical-grade NK cells for human trials of adoptive immunotherapy, but ex vivo proliferation has been limited by telomere shortening. We developed K562-based aAPCs with membrane-bound IL-21 (mbIL21) and assessed their ability to support human NK-cell proliferation. In contrast to mbIL15, mbIL21-expressing aAPCs promoted log-phase NK cell expansion without evidence of senescence for up to 6 weeks of culture. By day 21, parallel expansion of NK cells from 22 donors demonstrated a mean 47,967-fold expansion (median 31,747) when co-cultured with aAPCs expressing mbIL21 compared to 825-fold expansion (median 325) with mbIL15. Despite the significant increase in proliferation, mbIL21-expanded NK cells also showed a significant increase in telomere length compared to freshly obtained NK cells, suggesting a possible mechanism for their sustained proliferation. NK cells expanded with mbIL21 were similar in phenotype and cytotoxicity to those expanded with mbIL15, with retained donor KIR repertoires and high expression of NCRs, CD16, and NKG2D, but had superior cytokine secretion. The mbIL21-expanded NK cells showed increased transcription of the activating receptor CD160, but otherwise had remarkably similar mRNA expression profiles of the 96 genes assessed. mbIL21-expanded NK cells had significant cytotoxicity against all tumor cell lines tested, retained responsiveness to inhibitory KIR ligands, and demonstrated enhanced killing via antibody-dependent cell cytotoxicity. Thus, aAPCs expressing mbIL21 promote improved proliferation of human NK cells with longer telomeres and less senescence, supporting their clinical use in propagating NK cells for adoptive immunotherapy.