Intraperitoneal delivery of human natural killer cells for treatment of ovarian cancer in a mouse xenograft model

NK cell line modified to express a potent, DR5 specific variant of TRAIL, show enhanced cytotoxicity in ovarian cancer models

Objective

Ovarian cancer is a lethal gynaecological malignancy with unsatisfactory 5 year survival rates of 30-50 %. Cell immunotherapy is a promising new cancer treatment where immune cells, such as Natural Killer (NK) cells, are administered to enable the patient to fight cancer through direct cytotoxicity. NK cells orchestrate an adaptive immune response by enabling the release of tumour antigens. NK cell cytotoxicity and effector responses are largely driven by TRAIL engagement. In this study we investigated the cytotoxic potential of a human NK cell line that were modified to express a potent DR5 specific TRAIL variant. We hypothesised that this modification would enhance NK cell cytotoxicity against TRAIL sensitive and resistant ovarian cancer cell lines in vitro.

Methods

KHYG-1 human NK cells were modified with a TRAIL variant targeting DR5 (TRAILv-KHYG-1). Human ovarian cancer cell lines, OVCAR-3 and SKOV-3, were cultured with modified or non-modified NK cells at different effector:target (E:T) ratios for 4 or 16 h. Apoptosis was assessed by Annexin-APC and 7-AAD and measured using flow cytometry. Apoptotic cells were defined as annexin V 7-AAD double positive. Cytokine expression was measured by multiplex ELISA, and analysed by flow cytometry.

Results

Modified and non-modified NK cells significantly reduced OVCAR-3 cell viability as compared to OVCAR-3 cells that were cultured alone after 4 and 16 h treatment. OVCAR-3 cell viability was reduced after treatment with 1:1 E:T ratio with TRAILv-KHYG-1 cells after 16 h. On the contrary, neither NK cell line had any effect of SKOV-3 cell viability despite SKOV-3 cells having more DR5 surface expression compared to OVCAR-3 cells.

Conclusions

TRAILv-KHYG-1 cells significantly reduced OVCAR-3 cell viability as compared to non-modified NK cells. However, no significant reduction in viability was observed when SKOV-3 cell were cultured with either NK cells, despite having more DR5 surface expression compared to OVCAR-3 cells. These data indicate that mechanisms other than DR5 expression drive TRAIL resistance in ovarian cancer.

Exploring the Potential of Natural Killer Cell-Based Immunotherapy in Targeting High-Grade Serous Ovarian Carcinomas

High-grade serous ovarian cancers (HGSOCs) likely consist of poorly differentiated stem-like cells (PDSLCs) and differentiated tumor cells. Conventional therapeutics are incapable of completely eradicating PDSLCs, contributing to disease progression and tumor relapse. Primary NK cells are known to effectively lyse PDSLCs, but they exhibit low or minimal cytotoxic potential against well-differentiated tumors. We have introduced and discussed the characteristics of super-charged NK (sNK) cells in this review. sNK cells, in comparison to primary NK cells, exhibit a significantly higher capability for the direct killing of both PDSLCs and well-differentiated tumors. In addition, sNK cells secrete significantly higher levels of cytokines, especially those known to induce the differentiation of tumors. In addition, we propose that a combination of sNK and chemotherapy could be one of the most effective strategies to eliminate the heterogeneous population of ovarian tumors; sNK cells can lyse both PDSLCs and well-differentiated tumors, induce the differentiation of PDSLCs, and could be used in combination with chemotherapy to target both well-differentiated and NK-induced differentiated tumors.

Multichannel-optical imaging for in vivo evaluating the safety and therapeutic efficacy of stem cells in tumor model in terms of cell tropism, proliferation and NF-κB activity

Stem cell-based cancer treatment has garnered significant attention, yet its safety and efficacy remain incompletely understood. The nuclear factor-kappa B (NF-κB) pathway, a critical signaling mechanism involved in tumor growth, angiogenesis, and invasion, serves as an essential metric for evaluating the behavior of stem cells in tumor models. Herein, we report the development of a triple-channel imaging system capable of simultaneously monitoring the tropism of stem cells towards tumors, assessing tumor proliferation, and quantifying tumor NF-κB activity. In this system, we generated a CRISPR-Cas9 gene-edited human glioblastoma cell line, GE-U87-MG, which provided a reliable readout of the proliferation and NF-κB activity of tumors by EF1α-RFLuc- and NF-κB-GLuc-based bioluminescent imaging, respectively. Additionally, near infrared-II emitting Tat-PEG-AgAuSe quantum dots were developed for tracking of stem cell tropism towards tumor. In a representative case involving human mesenchymal stem cells (hMSCs), multichannel imaging revealed no discernible effect of hMSCs on the proliferation and NF-κB activity of GE-U87-MG tumors. Moreover, hMSCs engineered to overexpress the necrosis factor-related apoptosis-inducing ligand were able to inhibit NF-κB activity and growth of GE-U87-MG in vivo. Taken together, our imaging system represents a powerful and feasible approach to evaluating the safety and therapeutic efficacy of stem cells in tumor models.

Enhancing the therapeutic efficacy of NK cells in the treatment of ovarian cancer (Review)

Ovarian cancer is a prevalent gynecological malignancy associated with a high mortality rate and a low 5‑year survival rate. Typically, >70% of patients present with an advanced stage of the disease, resulting in a high number of ovarian cancer‑associated deaths worldwide. Over the past decade, adoptive cellular immunotherapy has been investigated in clinical trials, and the results have led to the increased use in cancer treatment. Natural killer (NK) cells are cytotoxic lymphoid cells that recognize and lyse transformed cells, thereby impeding tumor growth. Thus, NK cells exhibit potential as a form of immunotherapy in the treatment of cancer. However, some patients with ovarian cancer treated with NK cells have experienced unsatisfactory outcomes. Therefore, further optimization of NK cells is required to increase the number of patients achieving long‑term remission. In the present review article, studies focusing on improving NK cell function were systematically summarized, and innovative strategies that augment the anticancer properties of NK cells were proposed.

Ovarian cancer treatment and natural killer cell-based immunotherapy

Background

Ovarian cancer (OC) is one of the malignant tumors that poses a serious threat to women's health. Natural killer (NK) cells are an integral part of the immune system and have the ability to kill tumor cells directly or participate indirectly in the anti-tumor immune response. In recent years, NK cell-based immunotherapy for OC has shown remarkable potential. However, its mechanisms and effects remain unclear when compared to standard treatment.

Methods

To explore the value of NK cell-based immunotherapy in the treatment of OC, we conducted a literature review. In comparison to standard treatment, our focus was primarily on the current anti-tumor mechanisms, the clinical effect of NK cells against OC, factors affecting the structure and function of NK cells, and strategies to enhance the effectiveness of NK cells.

Results

We found that NK cells exert their therapeutic effects in OC through mechanisms such as antibody-dependent cell cytotoxicity, perforin release, and granule enzyme secretion. They also secrete IFN-γ and TNF-α or engage in Fas/FasL and TRAIL/TRAILR pathways, mediating the death of OC cells. In clinical trials, the majority of patients experienced disease stability with mild side effects after receiving NK cell-based immunotherapy, but there is still a lack of high-quality research evidence regarding its clinical effectiveness. OC and prior experience with standard treatments have an effect on NK cells, and it may be considered to maximize NK cell effects through the modulation of the tumor microenvironment or combination with other therapies.

Conclusions

In this review, we have summarized the current evidence of NK cell applications in the treatment of OC. Furthermore, factors and strategies that influence and enhance the role of NK cell immunotherapy are discussed.

iPSC-derived natural killer cells expressing the FcγR fusion CD64/16A can be armed with antibodies for multitumor antigen targeting

BACKGROUND

Antibody therapies can direct natural killer (NK) cells to tumor cells, tumor-associated cells, and suppressive immune cells to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). This antigen-specific effector function of human NK cells is mediated by the IgG Fc receptor CD16A (FcγRIIIA). Preclinical and clinical studies indicate that increasing the binding affinity and avidity of CD16A for antibodies improves the therapeutic potential of ADCC. CD64 (FcγRI), expressed by myeloid cells but not NK cells, is the only high affinity IgG Fc receptor and is uniquely capable of stably binding to free monomeric IgG as a physiological function. We have reported on the generation of the FcγR fusion CD64/16A, consisting of the extracellular region of CD64 and the transmembrane and cytoplasmic regions from CD16A, retaining its signaling and cellular activity. Here, we generated induced pluripotent stem cell (iPSC)-derived NK (iNK) cells expressing CD64/16A as a potential adoptive NK cell therapy for increased ADCC potency.

METHODS

iPSCs were engineered to express CD64/16A as well as an interleukin (IL)-15/IL-15Rα fusion (IL-15RF) protein and differentiated into iNK cells. iNK cells and peripheral blood NK cells were expanded using irradiated K562-mbIL21-41BBL feeder cells and examined. NK cells, ovarian tumor cell lines, and therapeutic monoclonal antibodies were used to assess ADCC in vitro, performed by a DELFIA EuTDA assay or in real-time by IncuCyte assays, and in vivo. For the latter, we developed a xenograft mouse model with high circulating levels of human IgG for more physiological relevance.

RESULTS

We demonstrate that (1) iNK-CD64/16A cells after expansion or thaw from cryopreservation can be coupled to therapeutic antibodies, creating armed iNK cells; (2) antibody-armed iNK-CD64/16A cells can be redirected by added antibodies to target new tumor antigens, highlighting additional potential of these cells; (3) cytokine-autonomous activity by iNK-CD64/16A cells engineered to express IL-15RF; and that (4) antibody-armed iNK-CD64/16A cells thawed from cryopreservation are capable of sustained and robust ADCC in vitro and in vivo, as determined by using a modified tumor xenograft model with high levels of competing human IgG.

CONCLUSIONS

iNK cells expressing CD64/16A provide an off-the-shelf multiantigen targeting platform to address tumor heterogeneity and mitigate antigen escape.

Analysis of NK-92 cytotoxicity in nasopharyngeal carcinoma cell lines and patient-derived xenografts using impedance-based growth method

Natural killer (NK) cells are innate immune cells that can remove viral-infected tumour cells without antigen priming. This characteristic offers NK cells an edge over other immune cells as a potential therapy for nasopharyngeal carcinoma (NPC). In this study, we report how cytotoxicity was evaluated in target NPC cell lines and patient-derived xenograft (PDX) cells with effector NK-92, a commercially available NK cell line, by using xCELLigence RTCA system (a real-time, label-free impedance-based monitoring platform). Cell viability, proliferation and cytotoxicity were examined by RTCA. Cell morphology, growth and cytotoxicity were also monitored by microscopy. RTCA and microscopy showed that both target and effector cells were able to proliferate normally and to maintain original morphology in co-culture medium as they were in their own respective culture medium. As target and effector (T:E) cell ratios increased, cell viability as measured by arbitrary cell index (CI) values in RTCA decreased in all cell lines and PDX cells. NPC PDX cells were more sensitive to the cytotoxicity effect of NK-92 cells, than the NPC cell lines. These data were substantiated by GFP-based microscopy. We have shown how the RTCA system can be used for a high throughput screening of the effects of NK cells in cancer studies to obtain data such as cell viability, proliferation and cytotoxicity.

Immunotherapy for Peritoneal Carcinomatosis: Challenges and Prospective Outcomes

Peritoneal metastasis, also known as peritoneal carcinomatosis (PC), is a refractory cancer that is typically resistant to conventional therapies. The typical treatment for PC is a combination of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Recently, research in this area has seen significant advances, particularly in immunotherapy as an alternative therapy for PC, which is very encouraging. Catumaxomab is a trifunctional antibody intraperitoneal (IP) immunotherapy authorized in Europe that can be used to diminish malignant ascites by targeting EpCAM. Intraperitoneal (IP) immunotherapy breaks immunological tolerance to treat peritoneal illness. Increasing T-cell responses and vaccination against tumor-associated antigens are two methods of treatment. CAR-T cells, vaccine-based therapeutics, dendritic cells (DCs) in combination with pro-inflammatory cytokines and NKs, adoptive cell transfer, and immune checkpoint inhibitors are promising treatments for PC. Carcinoembryonic antigen-expressing tumors are suppressed by IP administration of CAR-T cells. This reaction was strengthened by anti-PD-L1 or anti-Gr1. When paired with CD137 co-stimulatory signaling, CAR-T cells for folate receptor cancers made it easier for T-cell tumors to find their way to and stay alive in the body.

Natural killer cells in sepsis: Friends or foes?

Sepsis is one of the major causes of death in the hospital worldwide. The pathology of sepsis is tightly associated with dysregulation of innate immune responses. The contribution of macrophages, neutrophils, and dendritic cells to sepsis is well documented, whereas the role of natural killer (NK) cells, which are critical innate lymphoid lineage cells, remains unclear. In some studies, the activation of NK cells has been reported as a risk factor leading to severe organ damage or death. In sharp contrast, some other studies revealed that triggering NK cell activity contributes to alleviating sepsis. In all, although there are several reports on NK cells in sepsis, whether they exert detrimental or protective effects remains unclear. Here, we will review the available experimental and clinical studies about the opposing roles of NK cells in sepsis, and we will discuss the prospects for NK cell-based immunotherapeutic strategies for sepsis.

Expanded natural killer cells potentiate the antimyeloma activity of daratumumab, lenalidomide, and dexamethasone in a myeloma xenograft model

The development of new treatment agents in recent decades has significantly improved the survival of patients with multiple myeloma (MM). Nonetheless, MM remains an incurable disease; therefore, novel combination therapies are required. Natural killer (NK) cells are one of the safest immunotherapeutic options. In this study, we found that the anti-myeloma activity of expanded NK cells (eNKs) was improved by daratumumab, lenalidomide, and dexamethasone (DRd) in an MM xenograft mouse model. NK cells expanded from peripheral blood mononuclear cells collected from MM patients were highly cytotoxic against DRd pretreated tumor cells in vitro. To mimic the clinical protocol, a human MM xenograft model was developed using human RPMI8226-RFP-FLuc cells in NOD/SCID IL-2Rγnull (NSG) mice. MM bearing mice were randomly divided into six groups: no treatment, eNK, Rd, Rd + eNKs, DRd, and DRd + eNKs. DRd significantly enhanced the cytotoxicity of eNKs by upregulating NK cell activation ligands and effector function. DRd in combination with eNKs significantly reduced the serum M-protein level and prolonged mouse survival. In addition, DRd significantly increased the persistence of eNK and homing to MM sites. These results show that the anti-myeloma activity of ex vivo-expanded and activated NK cells is augmented by the immunomodulatory effect of DRd in MM-bearing mice, suggesting the therapeutic potential of this combination for MM patients.

Chemo-immune cell therapy by intratumoral injection of adoptive NK cells with capecitabine in gastric cancer xenograft model

Introduction

Gastric cancer is one of the most commonly known malignancies and is the fifth cancer-related death globally. Whereas natural killer (NK) cells play a critical role in tumor elimination; therefore, adoptive NK cell therapy has become a promising approach in cancer cytotherapy. Hence, this study investigated the chemo-immune cell therapy in MKN-45 derived xenograft gastric cancer model.

Methods

Three groups of animals have received the following treatments separately: activated NK cells, capecitabine, the combination of capecitabine and activated NK cells, and one was considered as the control group. Morphometric properties of tumor samples were evaluated at the end of the study. NK cells infiltration was evaluated by immunohistochemistry (IHC) of hCD56. Mitotic count and treatment response was assessed by hematoxylin and eosin (H&E) staining. The proliferation ratio to apoptosis was determined by IHC assessment of Ki67 and caspase 3.

Results

The results indicated that the NK cell therapy could effectively decrease the mitotic count in pathology assessment, but the tumor was not completely eradicated. In combination with metronomic chemotherapy (MC) of capecitabine, NK cell therapy demonstrated a significant difference in tumor morphometric properties compared to the control group. The proliferation ratio to apoptosis was also in line with pathology data.

Conclusion

Although NK cell therapy could effectively decrease the mitotic count in vivo, the obtained findings indicated lesser potency than MC despite ex vivo activation. In order to enhance NK cell therapy effectiveness, suppressive features of the tumor microenvironment and inhibitory immune checkpoints blockade should be considered.

Peritoneal carcinomatosis with intraperitoneal immunotherapy: current treatment options and perspectives

INTRODUCTION

Peritoneal carcinomatosis (PC) is an advanced malignancy that is not sensitive to systemic conventional chemotherapy. Treatment options for PC are usually palliative rather than curative. Cytoreductive surgery and hyperthermic intraperitoneal (IP) chemotherapy are associated with limited efficacy in patients with PC. However, the peritoneum can produce effective immunity by inducing T-lymphocyte recruitment and proliferation, and the unique immune environment of the peritoneum provides the rationale for IP immunotherapy in PC.

AREAS COVERED

The authors retrieved relevant documents of IP immunotherapy for PC from PubMed and Medline. This review elaborates on the knowledge of the peritoneal immune microenvironment and IP immunotherapy for PC covering immune stimulators, radioimmunotherapy, catumaxomab, cancer vaccines, chimeric antigen receptor (CAR)-T cells, and immune checkpoint inhibitors.

EXPERT OPINION

The prognosis of PC is poor. However, the peritoneal cavity is a unique immune compartment with abundant immune cells which can produce effective immunity. IP immunotherapy may be a promising strategy in patients with PC.

The adipocyte microenvironment and cancer

Many epithelial tumors grow in the vicinity of or metastasize to adipose tissue. As tumors develop, crosstalk between adipose tissue and cancer cells leads to changes in adipocyte function and paracrine signaling, promoting a microenvironment that supports tumor growth. Over the last decade, it became clear that tumor cells co-opt adipocytes in the tumor microenvironment, converting them into cancer-associated adipocytes (CAA). As adipocytes and cancer cells engage, a metabolic symbiosis ensues that is driven by bi-directional signaling. Many cancers (colon, breast, prostate, lung, ovarian cancer, and hematologic malignancies) stimulate lipolysis in adipocytes, followed by the uptake of fatty acids (FA) from the surrounding adipose tissue. The FA enters the cancer cell through specific fatty acid receptors and binding proteins (e.g., CD36, FATP1) and are used for membrane synthesis, energy metabolism (β-oxidation), or lipid-derived cell signaling molecules (derivatives of arachidonic and linolenic acid). Therefore, blocking adipocyte-derived lipid uptake or lipid-associated metabolic pathways in cancer cells, either with a single agent or in combination with standard of care chemotherapy, might prove to be an effective strategy against cancers that grow in lipid-rich tumor microenvironments.

Anti-Tumor Activity of Expanded PBMC-Derived NK Cells by Feeder-Free Protocol in Ovarian Cancer

Natural killer (NK) cells have shown great therapeutic potential against a wide range of cancers due to their pan-specific target recognition. Numerous reports indicate that NK cell immunotherapy is an effective therapeutic approach for treating hematological malignancies, but shows limited effects against solid tumors. In this study, several models of ovarian cancer (OC) were used to test the anti-cancer effects of NK cells derived from human peripheral blood mononuclear cells and expanded using a feeder cell-free expansion system (eNKs). The results show that eNKs exhibit potent inhibitory activity on tumor growth in different ovarian cancer xenograft mice (i.e., solid tumors, abdominal metastatic tumors, and ascites), importantly, in a dose-dependent manner. Moreover, adoptive transfer of eNKs resulted in significant reduction in ascites formation in OC peritoneal tumor models, and especially in reducing intraperitoneal ascites. We found that eNKs could migrate to the tumor site, retain their activity, and proliferate to maintain high cell counts in cutaneous xenograft mice. In addition, when increased the infusion with a high dose of 12 × 107 cells/mouse, Graft-versus-host disease could be induced by eNK. These data show that eNK cell immunotherapy could be a promising treatment strategy for ovarian cancers, including solid tumors and ascites.

Stem-cell based, machine learning approach for optimizing natural killer cell-based personalized immunotherapy for high-grade ovarian cancer

Advanced high-grade serous ovarian cancer continues to be a therapeutic challenge for those affected using the current therapeutic interventions. There is an increasing interest in personalized cancer immunotherapy using activated natural killer (NK) cells. NK cells account for approximately 15% of circulating white blood cells. They are also an important element of the tumor microenvironment (TME) and the body's immune response to cancers. In the present study, DeepNEU-C2Rx, a machine learning platform, was first used to create validated artificially induced pluripotent stem cell simulations. These simulations were then used to generate wild-type artificially induced NK cells (aiNK-WT) and TME simulations. Once validated, the aiNK-WT simulations were exposed to artificially induced high-grade serous ovarian cancer represented by aiOVCAR3. Cytolytic activity of aiNK was evaluated in presence and absence of aiOVCAR3 and data were compared with the literature for validation. The TME simulations suggested 26 factors that could be evaluated based on their ability to enhance aiNK-WT cytolytic activity in the presence of aiOVCAR3. The addition of programmed cell death-1 inhibitor leads to significant reinvigoration of aiNK cytolytic activity. The combination of programmed cell death-1 and glycogen synthase kinase 3 inhibitors showed further improvement. Further addition of ascitic fluid factor inhibitors leads to optimal aiNK activation. Our data showed that NK cell simulations could be used not only to pinpoint novel immunotherapeutic targets to reinvigorate the activity of NK cells against cancers, but also to predict the outcome of targeting tumors with specific genetic expression and mutation profiles.

Expanded natural killer cells augment the antimyeloma effect of daratumumab, bortezomib, and dexamethasone in a mouse model

The use of natural killer (NK) cells is a promising and safe immunotherapeutic approach in the field of cancer immunotherapy. However, combination treatments are required to enhance the effector functions and therapeutic efficacy of NK cells. In this study, we investigated the potential of daratumumab (Dara), bortezomib, and dexamethasone (Dvd) to augment the antitumor effects of NK cells in a multiple myeloma (MM) xenograft mouse model. NK cells were expanded and activated using the K562-OX40 ligand and membrane-bound IL-18 and IL-21 in the presence of IL-2 and IL-15 from peripheral blood mononuclear cells from MM patients. A human MM xenograft model was established using human RPMI8226-RFP-FLuc cells in NOD/SCID IL-2Rγ^null (NSG) mice. Tumor-bearing mice were divided into six treatment groups: no treatment, expanded NK cells (eNKs), Dara, Dara + eNKs, Dvd, and Dvd + eNKs. Dvd treatment strongly enhanced the cytotoxicity of eNKs by upregulating expression of NK cell activation ligands, downregulating expression of NK cell inhibitory ligands, and promoting antibody-dependent cellular cytotoxicity. The combination of eNKs with Dvd significantly prolonged mouse survival and reduced the tumor burden and serum M-protein level. Furthermore, Dvd pretreatment significantly increased eNK persistence and homing to MM sites. Our findings suggest that Dvd treatment potentiates the antimyeloma effects of NK cells expanded and activated ex vivo by modulating immune responses in MM-bearing mice.

Live cell imaging of highly activated natural killer cells against human hepatocellular carcinoma in vivo

BACKGROUND AIMS

Tracking administered natural killer (NK) cells in vivo is critical for developing an effective NK cell-based immunotherapy against human hepatocellular carcinoma (HCC). Here the authors established a new molecular imaging using ex vivo-activated NK cells and investigated real-time biodistribution of administered NK cells during HCC progression.

METHODS

Ex vivo-expanded NK cells from healthy donors were labeled with a near-infrared lipophilic cytoplasmic dye, and their proliferation, surface receptor expression and cytotoxicity activity were evaluated. Human HCC HepG2 cells were implanted into the livers of NOD.Cg-Prkdc^scid IL2rg^tm1Wjl/SzJ (NSG) mice. The authors administered 1,1'-dioctadecyltetramethyl indotricarbocyanine iodide (DiR)-labeled NK cells intravenously to non-tumor-bearing and intrahepatic HCC tumor-bearing NSG mice. Fluorescent imaging was performed using a fluorescence-labeled organism bioimaging instrument. Single cell suspensions from the resected organs were analyzed using flow cytometry.

RESULTS

The fluorescent DiR dye was nontoxic and did not affect the proliferation or surface receptor expression levels of the NK cells, even at high doses. The administered DiR-labeled NK cells immediately migrated to the lungs of the non-tumor-bearing NSG mice, with increased NK cell signals evident in the liver and spleen after 4 h. NK cells migrated to the intrahepatic tumor-bearing livers of both early- and late-stage HCC mice within 1 h of injection. In early-stage intrahepatic tumor-bearing mice, the fluorescence signal increased in the liver until 48 h post-injection and decreased 7 days after NK injection. In late-stage HCC, the NK cell fluorescence signal was the highest in the liver for 7 days after NK injection and persisted for 14 days. The purity of long-term persistent CD45⁺CD56⁺CD3^- NK cells was highest in early- and late-stage HepG2-bearing liver compared with normal liver 2 weeks after NK injection, whereas highest purity was still observed in the lungs of non-tumor-bearing mice. In addition, Ki-67 expression was detected in migrated human NK cells in the liver and lung up to 72 h after administration. With HepG2 tumor progression, NK cells reduced the expression of NKp30 and NKG2D.

CONCLUSIONS

Administered NK cells were successfully tracked in vivo by labeling the NK cells with near-infrared DiR dye. Highly expanded, activated NK cells migrated rapidly to the tumor-bearing liver, where they persisted for 14 days after administration, with high purity of CD45⁺CD56⁺CD3^- NK cells. Liver biodistribution and persistence of administered NK cells showed significantly different accumulation patterns during HCC progression.

Development of humanized mouse with patient-derived xenografts for cancer immunotherapy studies: A comprehensive review

Immunotherapy has revolutionized cancer treatment, however, not all tumor types and patients are completely responsive to this approach. Establishing predictive pre-clinical models would allow for more accurate and practical immunotherapeutic drug development. Mouse models are extensively used as in vivo system for biomedical research. However, due to the significant differences between rodents and human, it is impossible to translate most of the findings from mouse models to human. Pharmacological development and advancing personalized medicine using patient-derived xenografts relies on producing mouse models in which murine cells and genes are substituted with their human equivalent. Humanized mice (HM) provide a suitable platform to evaluate xenograft growth in the context of a human immune system. In this review, we discussed recent advances in the generation and application of HM models. We also reviewed new insights into the basic mechanisms, pre-clinical evaluation of onco-immunotherapies, current limitations in the application of these models as well as available improvement strategies. Finally, we pointed out some issues for future studies.

NK cell-based cancer immunotherapy: from basic biology to clinical development

Natural killer (NK) cell is a specialized immune effector cell type that plays a critical role in immune activation against abnormal cells. Different from events required for T cell activation, NK cell activation is governed by the interaction of NK receptors with target cells, independent of antigen processing and presentation. Due to relatively unsophisticated cues for activation, NK cell has gained significant attention in the field of cancer immunotherapy. Many efforts are emerging for developing and engineering NK cell-based cancer immunotherapy. In this review, we provide our current understandings of NK cell biology, ongoing pre-clinical and clinical development of NK cell-based therapies and discuss the progress, challenges, and future perspectives.

TIGIT blockade enhances functionality of peritoneal NK cells with altered expression of DNAM-1/TIGIT/CD96 checkpoint molecules in ovarian cancer

Advanced ovarian cancer (OC) patients have a poor 5-year survival of only 28%, emphasizing the medical need for improved therapies. Adjuvant immunotherapy could be an attractive approach since OC is an immunogenic disease and the presence of tumor-infiltrating lymphocytes has shown to positively correlate with patient survival. Among these infiltrating lymphocytes are natural killer (NK) cells, key players involved in tumor targeting, initiated by signaling via activating and inhibitory receptors. Here, we investigated the role of the DNAM-1/TIGIT/CD96 axis in the anti-tumor response of NK cells toward OC. Ascites-derived NK cells from advanced OC patients showed lower expression of activating receptor DNAM-1 compared to healthy donor peripheral blood NK cells, while inhibitory receptor TIGIT and CD96 expression was equal or higher, respectively. This shift to a more inhibitory phenotype could also be induced in vitro by co-culturing healthy donor NK cells with OC tumor spheroids, and in vivo on intraperitoneally infused NK cells in SKOV-3 OC bearing NOD/SCID-IL2Rγnull (NSG) mice. Interestingly, TIGIT blockade enhanced degranulation and interferon gamma (IFNγ) production of healthy donor CD56^dim NK cells in response to OC tumor cells, especially when DNAM-1/CD155 interactions were in place. Importantly, TIGIT blockade boosted functional responsiveness of CD56^dim NK cells of OC patients with a baseline reactivity against SKOV-3 cells. Overall, our data show for the first time that checkpoint molecules TIGIT/DNAM-1/CD96 play an important role in NK cell responsiveness against OC, and provides rationale for incorporating TIGIT interference in NK cell-based immunotherapy in OC patients.

Enhancing delivery of small molecule and cell-based therapies for ovarian cancer using advanced delivery strategies

Ovarian cancer is the most lethal gynecological malignancy with a global five-year survival rate of 30-50%. First-line treatment involves cytoreductive surgery and administration of platinum-based small molecules and paclitaxel. These therapies were traditionally administered via intravenous infusion, although intraperitoneal delivery has also been investigated. Initial clinical trials of intraperitoneal administration for ovarian cancer indicated significant improvements in overall survival compared to intravenous delivery, but this result is not consistent across all studies performed. Recently cell-based immunotherapy has been of interest for ovarian cancer. Direct intraperitoneal delivery of cell-based immunotherapies might prompt local immunoregulatory mechanisms to act synergistically with the delivered immunotherapy. Based on this theory, pre-clinical in vivo studies have delivered these cell-based immunotherapies via the intraperitoneal route, with promising results. However, successful intraperitoneal delivery of cell-based immunotherapy and clinical adoption of this technique will depend on overcoming challenges of intraperitoneal delivery and finding the optimal combinations of dose, therapeutic and delivery route. We review the potential advantages and disadvantages of intraperitoneal delivery of cell-based immunotherapy for ovarian cancer and the pre-clinical and clinical work performed so far. Potential advanced delivery strategies, which might improve the efficacy and adoption of intraperitoneal delivery of therapy for ovarian cancer, are also outlined.

Harnessing natural killer cells for the treatment of ovarian cancer

INTRODUCTION

Adoptive cellular immunotherapy could be an interesting new treatment option for ovarian carcinoma (OC), as research has demonstrated that OC is an immunogenic disease. In particular, natural killer (NK) cells have attracted attention due to their ability to kill tumor cells without prior sensitization. The therapeutic value of allogeneic NK cells has been first observed in hematological cancers and is increasingly being explored in solid tumors.

METHODS

To substantiate the rationale for NK cell therapy in OC we performed a literature search in the Pubmed database and in the international trial register clinicaltrials.gov with attention for the effect of OC on NK cell function, the effect of current treatment on NK cell biology and the evidence on the therapeutic value of NK cell therapy against OC.

RESULTS

In six clinical trials only 31 OC patients have been reported that received NK cell adoptive transfer. The majority of patients reached stable disease after NK cell therapy, with a mild pattern of side effects. In patients who received repeated infusions, more complete responses are described. All reported studies investigated the intravenous infusion of NK cells. Whereas the studies that are currently recruiting, investigate intraperitoneal infusion of allogeneic NK cells.

CONCLUSION

In this review the pre-clinical evidence and current trials on NK cell immunotherapy in OC patients are summarized. Furthermore, challenges that have to be overcome for NK cell adoptive therapy to have a significant impact on disease outcome are discussed.

CXCR1 Expression to Improve Anti-Cancer Efficacy of Intravenously Injected CAR-NK Cells in Mice with Peritoneal Xenografts

One reason underlying the failure of current chimeric antigen receptor (CAR) immune therapy to treat solid tumors adequately is insufficient tumor infiltration of CAR immune cells. To address the issue, we electroporated natural killer (NK) cells with two mRNA constructs encoding the chemokine receptor CXCR1 and a CAR targeting tumor-associated NKG2D ligands. The CXCR1-modified NK cells displayed increased migration toward tumor supernatants in vitro and augmented infiltration into human tumors in vivo in subcutaneous and intraperitoneal xenograft models. Most importantly, the cytotoxicity of the CAR-NK cells was not affected by CXCR1 transgene expression, and the enhanced tumor trafficking following intravenous injection resulted in significantly increased antitumor responses in mice carrying established peritoneal ovarian cancer xenografts. Collectively, our findings suggest that the coexpression of CXCR1 and a CAR may provide a novel strategy to enhance therapeutic efficacy of NK cells against solid cancers.

Human macrophages and innate lymphoid cells: Tissue-resident innate immunity in humanized mice

Macrophages and innate lymphoid cells (ILCs) are tissue-resident cells that play important roles in organ homeostasis and tissue immunity. Their intricate relationship with the organs they reside in allows them to quickly respond to perturbations of organ homeostasis and environmental challenges, such as infection and tissue injury. Macrophages and ILCs have been extensively studied in mice, yet important species-specific differences exist regarding innate immunity between humans and mice. Complementary to ex-vivo studies with human cells, humanized mice (i.e. mice with a human immune system) offer the opportunity to study human macrophages and ILCs in vivo within their surrounding tissue microenvironments. In this review, we will discuss how humanized mice have helped gain new knowledge about the basic biology of these cells, as well as their function in infectious and malignant conditions. Furthermore, we will highlight active areas of investigation related to human macrophages and ILCs, such as their cellular heterogeneity, ontogeny, tissue residency, and plasticity. In the near future, we expect more fundamental discoveries in these areas through the combined use of improved humanized mouse models together with state-of-the-art technologies, such as single-cell RNA-sequencing and CRISPR/Cas9 genome editing.

EGFR-Specific Tyrosine Kinase Inhibitor Modifies NK Cell-Mediated Antitumoral Activity against Ovarian Cancer Cells

The adverse prognosis of most patients with ovarian cancer is related to recurrent disease caused by resistance to chemotherapeutic and targeted therapeutics. Besides their direct activity against tumor cells, monoclonal antibodies and tyrosine kinase inhibitors (TKIs) also influence the antitumoral activity of immune cells, which has important implications for the design of immunotherapies. In this preclinical study, we treated different ovarian cancer cell lines with anti-epidermal growth factor receptor (EGFR) TKIs and co-incubated them with natural killer (NK) cells. We studied treatment-related structural and functional changes on tumor and immune cells in the presence of the anti-EGFR antibody cetuximab and investigated NK-mediated antitumoral activity. We show that long-term exposure of ovarian cancer cells to TKIs leads to reduced responsiveness of intrinsically sensitive cancer cells over time. Inversely, neither long-term treatment with TKIs nor cetuximab could overcome the intrinsic resistance of certain ovarian cancer cells to anti-EGFR agents. Remarkably, tumor cells pretreated with anti-EGFR TKIs showed increased sensitivity towards NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC). In contrast, the cytokine secretion of NK cells was reduced by TKI sensitization. Our data suggest that sensitization of tumor cells by anti-EGFR TKIs differentially modulates interactions with NK cells. These data have important implications for the design of chemo-immuno combination therapies in this tumor entity.

Cellular Therapies for the Treatment of Hematological Malignancies; Swine Are an Ideal Preclinical Model

The absence of clinically relevant large animal tumor models has historically forced experimental cellular therapies for hematological malignancies to translate directly from murine models to clinical trials. However, recent advances highlight swine as an ideal large animal model to demonstrate the safety of murine proof of concept studies prior to their implementation clinically. The availability of the MHC defined MGH miniature swine herd has been key for the development of novel approaches for hematopoietic cell and solid organ transplantation. New spontaneously arising hematological malignancies in these swine, specifically myeloid leukemias and B cell lymphomas, resemble human malignancies, which has allowed for development of immortalized tumor cell lines and has implications for the development of a large animal transplantable tumor model. The novel development of a SCID swine model has further advanced the field of large animal cancer models, allowing for engraftment of human tumor cells in a large animal model. Here, we will highlight the advantages of the swine pre-clinical model for the study of hematological malignancies. Further, we will discuss our experience utilizing spontaneously arising tumors in MGH swine to create a transplantable tumor model, describe the potential of the immunodeficient swine model, and highlight several novel cellular and biological therapies for the treatment of hematological malignancies in swine as a large animal pre-clinical bridge.

Cytokine-induced memory-like natural killer cells have enhanced function, proliferation, and in vivo expansion against ovarian cancer cells

OBJECTIVE

Natural killer (NK) cells are lymphocytes well suited for adoptive immunotherapy. Attempts with adoptive NK cell immunotherapy against ovarian cancer have proven unsuccessful, with the main limitations including failure to expand and diminished effector function. We investigated if incubation of NK cells with interleukin (IL)-12, IL-15, and IL-18 for 16h could produce cytokine-induced memory-like (CIML) NK cells capable of enhanced function against ovarian cancer.

METHODS

NK cells were preactivated briefly with IL-12, IL-15, and IL-18, rested, then placed against ovarian cancer targets to assess phenotype and function via flow cytometry. Real-time NK-cell-mediated tumor-killing was evaluated. Using ascites cells and cell-free ascites fluid, NK cell proliferation and function within the immunosuppressive microenvironment was evaluated in vitro. Finally, CIML NK cells were injected intraperitoneal (IP) into an in vivo xenogeneic mouse model of ovarian cancer.

RESULTS

CIML NK cells demonstrate enhanced cytokine (IFN-γ) production and NK-cell-mediated killing of ovarian cancer. NK cells treated overnight with cytokines led to robust activation characterized by temporal shedding of CD16, induction of CD25, and enhanced proliferation. CIML NK cells proliferate more with enhanced effector function compared to controls in an immunosuppressive microenvironment. Finally, human CIML NK cells exhibited potent antitumor effects within a xenogeneic mouse model of ovarian cancer.

CONCLUSIONS

CIML NK cells have enhanced functionality and persistence against ovarian cancer in vitro and in vivo, even when exposed to ascites fluid. These findings provide a strategy for NK cell-based immunotherapy to circumvent the immunosuppressive nature of ovarian cancer.

Humanized Mouse Models for the Preclinical Assessment of Cancer Immunotherapy

Immunotherapy is one of the most exciting recent breakthroughs in the field of cancer treatment. Many different approaches are being developed and a number have already gained regulatory approval or are under investigation in clinical trials. However, learning from the past, preclinical animal models often insufficiently reflect the physiological situation in humans, which subsequently causes treatment failures in clinical trials. Due to species-specific differences in most parts of the immune system, the transfer of knowledge from preclinical studies to clinical trials is eminently challenging. Human tumor cell line-based or patient-derived xenografts in immunocompromised mice have been successfully applied in the preclinical testing of cytotoxic or molecularly targeted agents, but naturally these systems lack the human immune system counterpart. The co-transplantation of human peripheral blood mononuclear cells or hematopoietic stem cells is employed to overcome this limitation. This review summarizes some important aspects of the different available tumor xenograft mouse models, their history, and their implementation in drug development and personalized therapy. Moreover, recent progress, opportunities and limitations of different humanized mouse models will be discussed.

Peritoneal NK cells are responsive to IL-15 and percentages are correlated with outcome in advanced ovarian cancer patients

The demonstration that ovarian carcinoma (OC) is an immunogenic disease, opens opportunities to explore immunotherapeutic interventions to improve clinical outcome. In this regard, NK cell based immunotherapy could be promising as it has been demonstrated that OC cells are susceptible to killing by cytokine-stimulated NK cells. Here, we evaluated whether percentage, phenotype, function and IL-15 responsiveness of ascites-derived natural killer (NK) cells is related to progression-free survival (PFS) and overall survival (OS) of advanced stage OC patients. Generally, a lower percentage of NK cells within the lymphocyte fraction was seen in OC ascites (mean 17.4 ± 2.7%) versus benign peritoneal fluids (48.1 ± 6.8%; p < 0.0001). Importantly, a higher CD56+ NK cell percentage in ascites was associated with a better PFS (p = 0.01) and OS (p = 0.002) in OC patients. Furthermore, the functionality of ascites-derived NK cells in terms of CD107a/IFN-γ activity was comparable to that of healthy donor peripheral blood NK cells, and stimulation with monomeric IL-15 or IL-15 superagonist ALT-803 potently improved their reactivity towards tumor cells. By showing that a higher NK cell percentage is related to better outcome in OC patients and NK cell functionality can be boosted by IL-15 receptor stimulation, a part of NK cell immunity in OC is further deciphered to exploit NK cell based immunotherapy.

PD-L1 blockade enhances anti-tumor efficacy of NK cells

Anti-PD-1/anti-PD-L1 therapies have shown success in cancer treatment but responses are limited to ~ 15% of patients with lymphocyte infiltrated, PD-L1 positive tumors. Hence, strategies that increase PD-L1 expression and tumor infiltration should make more patients eligible for PD-1/PD-L1 blockade therapy, thus improving overall outcomes. PD-L1 expression on tumors is induced by IFNγ, a cytokine secreted by NK cells. Therefore, we tested if PM21-particle expanded NK cells (PM21-NK cells) induced expression of PD-L1 on tumors and if anti-PD-L1 treatment enhanced NK cell anti-tumor efficacy in an ovarian cancer model. Studies here showed that PM21-NK cells secrete high amounts of IFNγ and that adoptively transferred PM21-NK cells induce PD-L1 expression on SKOV-3 cells in vivo. The induction of PD-L1 expression on SKOV-3 cells coincided with the presence of regulatory T cells (Tregs) in the abdominal cavity and within tumors. In in vitro experiments, anti-PD-L1 treatment had no direct effect on cytotoxicity or cytokine secretion by predominantly PD-1 negative PM21-NK cells in response to PD-L1⁺ targets. However, significant improvement of NK cell anti-tumor efficacy was observed in vivo when combined with anti-PD-L1. PD-L1 blockade also resulted in increased in vivo NK cell persistence and retention of their cytotoxic phenotype. These results support the use of anti-PD-L1 in combination with NK cell therapy regardless of initial tumor PD-L1 status and indicate that NK cell therapy would likely augment the applicability of anti-PD-L1 treatment.

Early Investigations and Recent Advances in Intraperitoneal Immunotherapy for Peritoneal Metastasis

Peritoneal metastasis (PM) is an advanced stage malignancy largely refractory to modern therapy. Intraperitoneal (IP) immunotherapy offers a novel approach for the control of regional disease of the peritoneal cavity by breaking immune tolerance. These strategies include heightening T-cell response and vaccine induction of anti-cancer memory against tumor-associated antigens. Early investigations with chimeric antigen receptor T cells (CAR-T cells), vaccine-based therapies, dendritic cells (DCs) in combination with pro-inflammatory cytokines and natural killer cells (NKs), adoptive cell transfer, and immune checkpoint inhibitors represent significant advances in the treatment of PM. IP delivery of CAR-T cells has shown demonstrable suppression of tumors expressing carcinoembryonic antigen. This response was enhanced when IP injected CAR-T cells were combined with anti-PD-L1 or anti-Gr1. Similarly, CAR-T cells against folate receptor α expressing tumors improved T-cell tumor localization and survival when combined with CD137 co-stimulatory signaling. Moreover, IP immunotherapy with catumaxomab, a trifunctional antibody approved in Europe, targets epithelial cell adhesion molecule (EpCAM) and has shown considerable promise with control of malignant ascites. Herein, we discuss immunologic approaches under investigation for treatment of PM.

Universal Chimeric Antigen Receptors for Multiplexed and Logical Control of T Cell Responses

T cells expressing chimeric antigen receptors (CARs) are promising cancer therapeutic agents, with the prospect of becoming the ultimate smart cancer therapeutics. To expand the capability of CAR T cells, here, we present a split, universal, and programmable (SUPRA) CAR system that simultaneously encompasses multiple critical "upgrades," such as the ability to switch targets without re-engineering the T cells, finely tune T cell activation strength, and sense and logically respond to multiple antigens. These features are useful to combat relapse, mitigate over-activation, and enhance specificity. We test our SUPRA system against two different tumor models to demonstrate its broad utility and humanize its components to minimize potential immunogenicity concerns. Furthermore, we extend the orthogonal SUPRA CAR system to regulate different T cell subsets independently, demonstrating a dually inducible CAR system. Together, these SUPRA CARs illustrate that multiple advanced logic and control features can be implemented into a single, integrated system.

Ex vivo-expanded NK cells from blood and ascites of ovarian cancer patients are cytotoxic against autologous primary ovarian cancer cells

Ovarian cancer (OC) is the leading cause of gynecological cancer-related death in North America. Most ovarian cancer patients (OCPs) experience disease recurrence after first-line surgery and chemotherapy; thus, there is a need for novel second-line treatments to improve the prognosis of OC. Although peripheral blood-derived NK cells are known for their ability to spontaneously lyse tumour cells without prior sensitization, ascites-derived NK cells (ascites-NK cells) isolated from OCPs exhibit inhibitory phenotypes, impaired cytotoxicity and may play a pro-tumourigenic role in cancer progression. Therefore, it is of interest to improve the cytotoxic effector function of impaired OCP ascites-NK cells at the tumour environment. We investigated the efficacy of using an artificial APC-based ex vivo expansion technique to generate cytotoxic, expanded NK cells from previously impaired OCP ascites-NK cells, for use in an autologous model of NK cell immunotherapy. We are the first to obtain a log-scale expansion of OCP ascites-NK cells that upregulate the surface expression of activating receptors NKG2D, NKp30, NKp44, produce robust amounts of anti-tumour cytokines in the presence of OC cells and mediate direct tumour cytotoxicity against ascites-derived, primary OC cells obtained from autologous patients. Our findings demonstrate that it is possible to generate cytotoxic OCP ascites-NK cells from previously impaired OCP ascites-NK cells, which presents a promising immunotherapeutic target for the second-line treatment of OC. Future work should focus on evaluating the in vivo efficacy of autologous NK cell immunotherapy through the intraperitoneal delivery of NK cell expansion factors to a preclinical xenograft mouse model of human OC.

Sestrin2 and sestrin3 suppress NK-92 cell-mediated cytotoxic activity on ovarian cancer cells through AMPK and mTORC1 signaling

Ovarian cancer is one of the major cancer types. NK-92 cell line, which has consistently and reproducibly high anti-tumor cytotoxicity, may be used for immunotherapy against ovarian cancer. Understanding the mechanisms that regulate the anti-tumor activity of NK-92 cells is important for developing novel therapeutic strategies. In the current study, using an ovarian cancer xenograft mouse model, we identified the up-regulation of sestrin2 (SESN2) and sestrin3 (SESN3) in intratumoral NK-92 cells. Lentivirus-transduced NK-92 cells, which overexpressed SESN2 or SESN3 after doxycycline treatment, exhibited less expression of activating receptors, perforin and granzyme B. Overexpression of SESN2 and SESN3 impaired tumoricidal effect of NK-92 cells both in vitro and in vivo. Furthermore, overexpression of SESN2 and SESN3 inhibited mTORC1 signaling while promoting AMPK signaling in NK-92 cells. Taken together, our data highlights the crucial effects of SESN2 and SESN3 on NK-92 cell-mediated anti-ovarian cancer activity. This study might be valuable for designing a novel therapeutic strategy for ovarian cancer.

Ex Vivo Expanded Human NK Cells Survive and Proliferate in Humanized Mice with Autologous Human Immune Cells

Adoptive immune cell therapy is emerging as a promising immunotherapy for cancer. Particularly, the adoptive transfer of NK cells has garnered attention due to their natural cytotoxicity against tumor cells and safety upon adoptive transfer to patients. Although strategies exist to efficiently generate large quantities of expanded NK cells ex vivo, it remains unknown whether these expanded NK cells can persist and/or proliferate in vivo in the absence of exogenous human cytokines. Here, we have examined the adoptive transfer of ex vivo expanded human cord blood-derived NK cells into humanized mice reconstituted with autologous human cord blood immune cells. We report that ex vivo expanded NK cells are able to survive and possibly proliferate in vivo in humanized mice without exogenous cytokine administration, but not in control mice that lack human immune cells. These findings demonstrate that the presence of autologous human immune cells supports the in vivo survival of ex vivo expanded human NK cells. These results support the application of ex vivo expanded NK cells in cancer immunotherapy and provide a translational humanized mouse model to test the lifespan, safety, and functionality of adoptively transferred cells in the presence of autologous human immune cells prior to clinical use.

Natural killer cell-mediated immunosurveillance of human cancer

The contribution of natural killer (NK) cells to immunosurveillance of human cancer remains debatable. Here, we discuss advances in several areas of human NK cell research, many of which support the ability of NK cells to prevent cancer development and avoid relapse following adoptive immunotherapy. We describe the molecular basis for NK cell recognition of human tumor cells and provide evidence for NK cell-mediated killing of human primary tumor cells ex vivo. Subsequently, we highlight studies demonstrating the ability of NK cells to migrate to, and reside in, the human tumor microenvironment where selection of tumor escape variants from NK cells can occur. Indirect evidence for NK cell immunosurveillance against human malignancies is provided by the reduced incidence of cancer in individuals with high levels of NK cell cytotoxicity, and the significant clinical responses observed following infusion of human NK cells into cancer patients. Finally, we describe studies showing enhanced tumor progression, or increased cancer incidence, in patients with inherited and acquired defects in cellular cytotoxicity. All these observations have in common that they, either indirectly or directly, suggest a role for NK cells in mediating immunosurveillance against human cancer. This opens up for exciting possibilities with respect to further exploring NK cells in settings of adoptive immunotherapy in human cancer.

Umbilical cord blood CD34+ progenitor-derived NK cells efficiently kill ovarian cancer spheroids and intraperitoneal tumors in NOD/SCID/IL2Rgnull mice

Adoptive transfer of allogeneic natural killer (NK) cells is an attractive therapy approach against ovarian carcinoma. Here, we evaluated the potency of highly active NK cells derived from human CD34+ haematopoietic stem and progenitor cells (HSPC) to infiltrate and mediate killing of human ovarian cancer spheroids using an in vivo-like model system and mouse xenograft model. These CD56+Perforin+ HSPC-NK cells were generated under stroma-free conditions in the presence of StemRegenin-1, IL-15, and IL-12, and exerted efficient cytolytic activity and IFNγ production toward ovarian cancer monolayer cultures. Live-imaging confocal microscopy demonstrated that these HSPC-NK cells actively migrate, infiltrate, and mediate tumor cell killing in a three-dimensional multicellular ovarian cancer spheroid. Infiltration of up to 30% of total HSPC-NK cells within 8 h resulted in robust tumor spheroid destruction. Furthermore, intraperitoneal HSPC-NK cell infusions in NOD/SCID-IL2Rγ^null (NSG) mice bearing ovarian carcinoma significantly reduced tumor progression. These findings demonstrate that highly functional HSPC-NK cells efficiently destruct ovarian carcinoma spheroids in vitro and kill intraperitoneal ovarian tumors in vivo, providing great promise for effective immunotherapy through intraperitoneal HSPC-NK cell adoptive transfer in ovarian carcinoma patients.

SCID pigs: An emerging large animal NK model

Severe Combined ImmunoDeficiency (SCID) is defined as the lack or impairment of an adaptive immune system. Although SCID phenotypes are characteristically absent of T and B cells, many such SCID cellular profiles include the presence of NK cells. In human SCID patients, functional NK cells may impact the engraftment success of life saving procedures such as bone marrow transplantation. However, in animal models, a T cell-, B cell-, NK cell+ environment provides a valuable tool for asking specific questions about the extent of the innate immune system function as well as emerging NK targeted therapies against cancer. Physiologically and immunologically the pig is more similar to the human than common rodent research animals. This review discusses why the T- B- NK+ SCID pig may offer a more relevant model for development of human SCID patient therapies as well as provide an opportunity for systematic exploration of the role of NK cells in artiodactyl immunity.

Modeling Natural Killer Cell Targeted Immunotherapies

Animal models have extensively contributed to our understanding of human immunobiology and to uncover the underlying pathological mechanisms occurring in the development of diseases. However, mouse models do not reproduce the genetic and molecular complexity inherent in human disease conditions. Human immune system (HIS) mouse models that are susceptible to human pathogens and can recapitulate human hematopoiesis and tumor immunobiology provide one means to bridge the interspecies gap. Natural killer cells are the founding member of the innate lymphoid cell family. They exert a rapid and strong immune response against tumor and pathogen-infected cells. Their antitumor features have long been exploited for therapeutic purposes in the context of cancer. In this review, we detail the development of highly immunodeficient mouse strains and the models currently used in cancer research. We summarize the latest improvements in adoptive natural killer (NK) cell therapies and the development of novel NK cell sources. Finally, we discuss the advantages of HIS mice to study the interactions between human NK cells and human cancers and to develop new therapeutic strategies.

IL-15 super-agonist (ALT-803) enhances natural killer (NK) cell function against ovarian cancer

OBJECTIVE

Natural killer (NK) cells represent a powerful immunotherapeutic target as they lyse tumors directly, do not require differentiation, and can elicit potent inflammatory responses. The objective of these studies was to use an IL-15 super-agonist complex, ALT-803 (Altor BioScience Corporation), to enhance the function of both normal and ovarian cancer patient derived NK cells by increasing cytotoxicity and cytokine production.

METHODS

NK cell function from normal donor peripheral blood mononuclear cells (PBMCs) and ovarian cancer patient ascites was assessed using flow cytometry and chromium release assays ±ALT-803 stimulation. To evaluate the ability of ALT-803 to enhance NK cell function in vivo against ovarian cancer, we used a MA148-luc ovarian cancer NOD scid gamma (NSG) xenogeneic mouse model with transferred human NK cells.

RESULTS

ALT-803 potently enhanced functionality of NK cells against all ovarian cancer cell lines with significant increases seen in CD107a, IFNγ and TNFα expression depending on target cell line. Function was also rescued in NK cells derived from ovarian cancer patient ascites. Finally, only animals treated with intraperitoneal ALT-803 displayed an NK dependent significant decrease in tumor.

CONCLUSIONS

ALT-803 enhances NK cell cytotoxicity against ovarian cancer in vitro and in vivo and is able to rescue functionality of NK cells derived from ovarian cancer patient ascites. These findings suggest that ALT-803 has the potential to enhance NK cell-based immunotherapeutic approaches for the treatment of ovarian cancer.

Anti-ovarian tumor response of donor peripheral blood mononuclear cells is due to infiltrating cytotoxic NK cells

Treatment of ovarian cancer, a leading cause of gynecological malignancy, has good initial efficacy with surgery and platinum/taxane-based chemotherapy, but poor long-term survival in patients. Inferior long-term prognosis is attributed to intraperitoneal spreading, relapse and ineffective alternate therapies. Adoptive cell therapy is promising for tumor remission, although logistical concerns impede widespread implementation. In this study, healthy PBMCs were used to examine the immune response in a mouse model with human ovarian cancer, where natural killer (NK) cells were found to be the effector cells that elicited an anti-tumor response. Presence of tumor was found to stimulate NK cell expansion in mice treated intraperitoneally with PBMC+Interleukin-2 (IL-2), as compared to no expansion in non-tumor-bearing mice given the same treatment. PBMC+IL-2 treated mice exhibiting NK cell expansion had complete tumor remission. To validate NK cell mediated anti-tumor response, the intratumoral presence of NK cells and their cytotoxicity was confirmed by immunohistochemistry and granzyme activity of NK cells recovered from the tumor. Collectively, this study highlights the significance of NK cell-cytotoxic response to tumor, which may be attributed to interacting immune cell types in the PBMC population, as opposed to clinically used isolated NK cells showing lack of anti-tumor efficacy in ovarian cancer patients.

Natural killer cells stimulated with PM21 particles expand and biodistribute in vivo: Clinical implications for cancer treatment

BACKGROUND AIMS

Natural killer (NK) cell immunotherapy for treatment of cancer is promising, but requires methods that expand cytotoxic NK cells that persist in circulation and home to disease site.

METHODS

We developed a particle-based method that is simple, effective and specifically expands cytotoxic NK cells from peripheral blood mononuclear cells (PBMCs) both ex vivo and in vivo. This method uses particles prepared from plasma membranes of K562-mb21-41BBL cells, expressing 41BBL and membrane bound interleukin-21 (PM21 particles).

RESULTS

Ex vivo, PM21 particles caused specific NK-cell expansion from PBMCs from healthy donors (mean 825-fold, range 163-2216, n = 13 in 14 days) and acute myeloid leukemia patients. The PM21 particles also stimulated in vivo NK cell expansion in NSG mice. Ex vivo pre-activation of PBMCs with PM21 particles (PM21-PBMC) before intraperitoneal (i.p.) injection resulted in 66-fold higher amounts of hNK cells in peripheral blood (PB) of mice compared with unactivated PBMCs on day 12 after injection. In vivo administration of PM21 particles resulted in a dose-dependent increase of PB hNK cells in mice injected i.p. with 2.0 × 10(6) PM21-PBMCs (11% NK cells). Optimal dose of 800 µg/injection of PM21 particles (twice weekly) with low-dose interleukin 2 (1000 U/thrice weekly) resulted in 470 ± 40 hNK/µL and 95 ± 2% of total hCD45(+) cells by day 12 in PB. Furthermore, hNK cells were found in marrow, spleen, lung, liver and brain (day 16 after i.p. PM21/PBMC injection), and mice injected with PM21 particles had higher amounts.

CONCLUSIONS

The extent of NK cells observed in PB, their persistence and the biodistribution would be relevant for cancer treatment.

Intraperitoneal immunotherapy: historical perspectives and modern therapy

Intraperitoneal immunotherapy represents a novel strategy for the management of peritoneal metastases (PM). Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) has remained the gold standard of treatment for patients with PM, yet despite optimal treatment, recurrence rates remain high and long-term survival poor. From Coley's toxins to immune checkpoint inhibitors, the wide variety of anticancer immunotherapeutic strategies are now garnering attention for control of regional disease of the peritoneal cavity. Early studies with vaccine-based therapies, adoptive cell transfer, immune checkpoint inhibitors, and chimeric T cells with tumor-specific antigen receptors (CAR-T cells) are being performed, showing promise for control of peritoneal spread and induction of lasting anticancer immunity. In addition, catumaxomab, a trifunctional antibody, has been approved for intraperitoneal immunotherapy in Europe for the control of malignant ascites in patients with epithelial cell adhesion molecule positive cancers. We review a brief history of immunotherapy and current modalities under investigation for intraperitoneal use in the treatment of PM.

Mouse Xenograft Model for Intraperitoneal Administration of NK Cell Immunotherapy for Ovarian Cancer

Natural killer (NK) cells are an attractive cell population for immunotherapy. Adoptive transfer of NK cells has been tested in multiple clinical trials including acute myeloid leukemia (AML) and ovarian cancer, although limitations do exist especially for treatment of solid tumors. In order to overcome these limitations, mouse xenograft models are needed for evaluation of various NK cell populations, as well as routes of NK cell administration. Here, we describe the methods used for the establishment of an intraperitoneal (ip) ovarian cancer mouse xenograft model with ip delivery of NK cells. This model has been successfully employed with multiple ovarian cell lines and could be applied to other tumor models where the tumor's primary location is in the peritoneal cavity. It is also compatible with multiple routes of NK cell administration. Bioluminescent imaging for monitoring tumor formation and response provides for easy visualization of NK cell tumor inhibition. This xenograft model is superior to other models because the tumor is implanted into the same physiological space where ovarian cancer is found, which allows for improved mimicking of actual disease.

Induced Pluripotent Stem Cell-Derived Natural Killer Cells for Treatment of Ovarian Cancer

Natural killer (NK) cells can provide effective immunotherapy for ovarian cancer. Here, we evaluated the ability of NK cells isolated from peripheral blood (PB) and NK cells derived from induced pluripotent stem cell (iPSC) to mediate killing of ovarian cancer cells in a mouse xenograft model. A mouse xenograft model was used to evaluate the intraperitoneal delivery of three different NK cell populations: iPSC-derived NK cells, PB-NK cells that had been activated and expanded in long-term culture, and overnight activated PB-NK cells that were isolated through CD3/CD19 depletion of PB B and T cells. Bioluminescent imaging was used to monitor tumor burden of luciferase expressing tumor lines. Tumors were allowed to establish prior to administering NK cells via intraperitoneal injection. These studies demonstrate a single dose of any of the three NK cell populations significantly reduced tumor burden. When mice were given three doses of either iPSC-NK cells or expanded PB-NK cells, the median survival improved from 73 days in mice untreated to 98 and 97 days for treated mice, respectively. From these studies, we conclude iPSC-derived NK cells mediate antiovarian cancer killing at least as well as PB-NK cells, making these cells a viable resource for immunotherapy for ovarian cancer. Due to their ability to be easily differentiated into NK cells and their long-term expansion potential, iPSCs can be used to produce large numbers of well-defined NK cells that can be banked and used to treat a large number of patients including treatment with multiple doses if necessary.

Preservation of tumor-host immune interactions with luciferase-tagged imaging in a murine model of ovarian cancer

BACKGROUND

Ovarian cancer is immunogenic and residual tumor volume after surgery is known to be prognostic. Ovarian cancer often follows a recurring-remitting course and microscopic disease states may present ideal opportunities for immune therapies. We sought to establish the immune profile of a murine model of ovarian cancer that allows in vivo tumor imaging and the quantitation of microscopic disease.

RESULTS AND DISCUSSION

Baseline imaging and weight measurements were taken within 1 and 2 weeks after intraperitoneal tumor injection, respectively. Significantly higher photons per second from baseline imaging were first observed 5 weeks after tumor cell injection (p < 0.05) and continued to be significant through 8 weeks after injection (p < 0.01), whereas a significant increase in weight above baseline was not observed until day 56 (p < 0.0001). Expression of luc2 in ID8 cells did not alter the cellular immune microenvironment of the tumor. FOXP3+ T cells were more likely to be detected in the intraepithelial compartment and CD4+ T cells in the stroma as compared to CD3+ T cells, which were found equally in stroma and intraepithelial compartments.

CONCLUSIONS

Use of an intraperitoneal tumor expressing a codon-optimized firefly luciferase in an immunocompetent mouse model allows tumor quantitation in vivo and detection of microscopic tumor burdens. Expression of this foreign protein does not significantly effect tumor engraftment or the immune microenvironment of the ID8 cells in vivo and may allow novel immunotherapies to be assessed in a murine model for their translational potential to ovarian cancers in remission or minimal disease after primary cytoreductive surgery or chemotherapy.

METHODS

Mouse ovarian surface epithelial cells from C57BL6 mice transformed after serial passage in vitro were transduced with a lentiviral vector expressing a codon optimized firefly luciferase (luc2). Cell lines were selected and luc2 expression functionally confirmed in vitro. Cell lines were intraperitoneally (IP) implanted in albino C57BL/6/BrdCrHsd-Tyrc mice and albino B6(Cg)-Tyrc-2 J/J mice for serial imaging. D-luciferin substrate was injected IP and tumors were serially imaged in vivo using a Xenogen IVIS. Tumor take, weights, and luminescent intensities were measured. Immunohistochemistry was performed on tumors and assessed for immune infiltrates in stromal and intraepithelial compartments.

Splenic B cells from Hymenolepis diminuta-infected mice ameliorate colitis independent of T cells and via cooperation with macrophages

Helminth parasites provoke multicellular immune responses in their hosts that can suppress concomitant disease. The gut lumen-dwelling tapeworm Hymenolepis diminuta, unlike other parasites assessed as helminth therapy, causes no host tissue damage while potently suppressing murine colitis. With the goal of harnessing the immunomodulatory capacity of infection with H. diminuta, we assessed the putative generation of anti-colitic regulatory B cells following H. diminuta infection. Splenic CD19(+) B cells isolated from mice infected 7 [HdBc(7(d))] and 14 d (but not 3 d) previously with H. diminuta and transferred to naive mice significantly reduced the severity of dinitrobenzene sulfonic acid (DNBS)-, oxazolone-, and dextran-sodium sulfate-induced colitis. Mechanistic studies with the DNBS model, revealed the anti-colitic HdBc(7(d)) was within the follicular B cell population and its phenotype was not dependent on IL-4 or IL-10. The HdBc(7(d)) were not characterized by increased expression of CD1d, CD5, CD23, or IL-10 production, but did spontaneously, and upon LPS plus anti-CD40 stimulation, produce more TGF-β than CD19(+) B cells from controls. DNBS-induced colitis in RAG1(-/-) mice was inhibited by administration of HdBc(7(d)), indicating a lack of a requirement for T and B cells in the recipient; however, depletion of macrophages in recipient mice abrogated the anti-colitic effect of HdBc(7(d)). Thus, in response to H. diminuta, a putatively unique splenic CD19(+) B cell with a functional immunoregulatory program is generated that promotes the suppression of colitis dominated by TH1, TH2, or TH1-plus-TH2 events, and may do so via the synthesis of TGF-β and the generation of, or cooperation with, a regulatory macrophage.