Cryopreserved Human Natural Killer Cells Exhibit Potent Antitumor Efficacy against Orthotopic Pancreatic Cancer through Efficient Tumor-Homing and Cytolytic Ability (Running Title: Cryopreserved NK Cells Exhibit Antitumor Effect)

Pretreatment with IL-15 and IL-18 rescues natural killer cells from granzyme B-mediated apoptosis after cryopreservation

Human natural killer (NK) cell-based therapies are under assessment for treating various cancers, but cryopreservation reduces both the recovery and function of NK cells, thereby limiting their therapeutic feasibility. Using cryopreservation protocols optimized for T cells, here we find that ~75% of NK cells die within 24 h post-thaw, with the remaining cells displaying reduced cytotoxicity. Using CRISPR-Cas9 gene editing and confocal microscopy, we find that cryopreserved NK cells largely die via apoptosis initiated by leakage of granzyme B from cytotoxic vesicles. Pretreatment of NK cells with a combination of Interleukins-15 (IL-15) and IL-18 prior to cryopreservation improves NK cell recovery to ~90-100% and enables equal tumour control in a xenograft model of disseminated Raji cell lymphoma compared to non-cryopreserved NK cells. The mechanism of IL-15 and IL-18-induced protection incorporates two mechanisms: a transient reduction in intracellular granzyme B levels via degranulation, and the induction of antiapoptotic genes.

Knockout of the inhibitory receptor TIGIT enhances the antitumor response of ex vivo expanded NK cells and prevents fratricide with therapeutic Fc-active TIGIT antibodies

BACKGROUND

Inhibitory receptor T-cell Immunoreceptor with Ig and ITIM domains (TIGIT) expressed by Natural Killer (NK) and T cells regulates cancer immunity and has been touted as the next frontier in the development of cancer immunotherapeutics. Although early results of anti-TIGIT and its combinations with antiprogrammed death-ligand 1 were highly exciting, results from an interim analysis of phase III trials are disappointing. With mixed results, there is a need to understand the effects of therapeutic anti-TIGIT on the TIGIT+ immune cells to support its clinical use. Most of the TIGIT antibodies in development have an Fc-active domain, which binds to Fc receptors on effector cells. In mouse models, Fc-active anti-TIGIT induced superior immunity, while Fc receptor engagement was required for its efficacy. NK-cell depletion compromised the antitumor immunity of anti-TIGIT indicating the essential role of NK cells in the efficacy of anti-TIGIT. Since NK cells express TIGIT and Fc-receptor CD16, Fc-active anti-TIGIT may deplete NK cells via fratricide, which has not been studied.

METHODS

CRISPR-Cas9-based TIGIT knockout (KO) was performed in expanded NK cells. Phenotypic and transcriptomic properties of TIGIT KO and wild-type (WT) NK cells were compared with flow cytometry, CyTOF, and RNA sequencing. The effect of TIGIT KO on NK-cell cytotoxicity was determined by calcein-AM release and live cell imaging-based cytotoxicity assays. The metabolic properties of TIGIT KO and WT NK cells were compared with a Seahorse analyzer. The effect of the Fc-component of anti-TIGIT on NK-cell fratricide was determined by co-culturing WT and TIGIT KO NK cells with Fc-active and Fc-inactive anti-TIGIT.

RESULTS

TIGIT KO increased the cytotoxicity of NK cells against multiple cancer cell lines including spheroids. TIGIT KO NK cells upregulated mTOR complex 1 (mTORC1) signaling and had better metabolic fitness with an increased basal glycolytic rate when co-cultured with cancer cells compared with WT NK cells. Importantly, TIGIT KO prevented NK-cell fratricide when combined with Fc-active anti-TIGIT.

CONCLUSIONS

TIGIT KO in ex vivo expanded NK cells increased their cytotoxicity and metabolic fitness and prevented NK-cell fratricide when combined with Fc-active anti-TIGIT antibodies. These fratricide-resistant TIGIT KO NK cells have therapeutic potential alone or in combination with Fc-active anti-TIGIT antibodies to enhance their efficacy.

Combinatorial immunotherapy with gemcitabine and ex vivo-expanded NK cells induces anti-tumor effects in pancreatic cancer

Pancreatic cancer is difficult to diagnose at the initial stage and is often discovered after metastasis to nearby organs. Gemcitabine is currently used as a standard treatment for pancreatic cancer. However, since chemotherapy for pancreatic cancer has not yet reached satisfactory therapeutic results, adjuvant chemotherapy methods are attempted. It can be expected that combining immune cell therapy with existing anticancer drug combination treatment will prevent cancer recurrence and increase survival rates. We isolated natural killer (NK) cells and co-cultured them with strongly activated autologous peripheral blood mononuclear cells (PBMCs) as feeder cells, activated using CD3 antibody, IFN-r, IL-2, and γ-radiation. NK cells expanded in this method showed greater cytotoxicity than resting NK cells, when co-cultured with pancreatic cancer cell lines. Tumor growth was effectively inhibited in a pancreatic cancer mouse xenograft model. Therapeutic efficacy was increased by using gemcitabine and erlotinib in combination. These findings suggest that NK cells cultured by the method proposed here have excellent anti-tumor activity. We demonstrate that activated NK cells can efficiently inhibit pancreatic tumors when used in combination with gemcitabine-based therapy.

TIGIT Expression on Activated NK Cells Correlates with Greater Anti-Tumor Activity but Promotes Functional Decline upon Lung Cancer Exposure: Implications for Adoptive Cell Therapy and TIGIT-Targeted Therapies

Treatments targeting TIGIT have gained a lot of attention due to strong preclinical and early clinical results, particularly with anti-PD-(L)1 therapeutics. However, this combination has failed to meet progression-free survival endpoints in phase III trials. Most of our understanding of TIGIT comes from studies of T cell function. Yet, this inhibitory receptor is often upregulated to the same, or higher, extent on NK cells in cancers. Studies in murine models have demonstrated that TIGIT inhibits NK cells and promotes exhaustion, with its effects on tumor control also being dependent on NK cells. However, there are limited studies assessing the role of TIGIT on the function of human NK cells (hNK), particularly in lung cancer. Most studies used NK cell lines or tested TIGIT blockade to reactivate exhausted cells obtained from cancer patients. For therapeutic advancement, a better understanding of TIGIT in the context of activated hNK cells is crucial, which is different than exhausted NK cells, and critical in the context of adoptive NK cell therapeutics that may be combined with TIGIT blockade. In this study, the effect of TIGIT blockade on the anti-tumor activities of human ex vivo-expanded NK cells was evaluated in vitro in the context of lung cancer. TIGIT expression was higher on activated and/or expanded NK cells compared to resting NK cells. More TIGIT⁺ NK cells expressed major activating receptors and exerted anti-tumor response as compared to TIGIT^- cells, indicating that NK cells with greater anti-tumor function express more TIGIT. However, long-term TIGIT engagement upon exposure to PVR⁺ tumors downregulated the cytotoxic function of expanded NK cells while the inclusion of TIGIT blockade increased cytotoxicity, restored the effector functions against PVR-positive targets, and upregulated immune inflammation-related gene sets. These combined results indicate that TIGIT blockade can preserve the activation state of NK cells during exposure to PVR⁺ tumors. These results support the notion that a functional NK cell compartment is critical for anti-tumor response and anti-TIGIT/adoptive NK cell combinations have the potential to improve outcomes.

Cytokine-Induced Killer Cell Immunotherapy Combined With Gemcitabine Reduces Systemic Metastasis in Pancreatic Cancer: An Analysis Using Preclinical Adjuvant Therapy-Mimicking Pancreatic Cancer Xenograft Model

OBJECTIVES

To evaluate the efficacy and safety of cytokine-induced killer (CIK) cell therapy in pancreatic cancer.

METHODS

An orthotopic murine model of pancreatic cancer and adjuvant therapy-mimicking xenograft murine model that underwent splenectomy was created. Eighty mice were randomized into four groups: the control, gemcitabine alone, CIK alone, and CIK with gemcitabine groups. The tumor growth was monitored using bioluminescence imaging once weekly.

RESULTS

In the orthotopic murine model, the treatment groups showed a significantly longer survival than the control group (median: not reached vs 125.0 days; 95% confidence interval, 119.87-130.13; P = 0.04); however, the overall survival did not differ significantly among the treatment groups (P = 0.779). The metastatic recurrence rate and overall survival were also not significantly different among the groups in the adjuvant therapy-mimicking xenograft murine model (P = 0.497). However, the CIK and gemcitabine combination suppressed the metastatic recurrence effectively, with recurrence-free survival being significantly longer in the CIK with gemcitabine group than in the control group (median, 54 days; 95% confidence interval, 25.00-102.00; P = 0.013).

CONCLUSIONS

The combination of CIK and gemcitabine suppressed systemic metastatic recurrence, with promising efficacy and good tolerability in an adjuvant setting of pancreatic cancer.

Cryopreserved PM21-Particle-Expanded Natural Killer Cells Maintain Cytotoxicity and Effector Functions In Vitro and In Vivo

There is a great interest in developing natural killer (NK) cells as adoptive cancer immunotherapy. For off-the-shelf approaches and to conduct multicenter clinical trials, cryopreserved NK cells are the preferred product. However, recent studies reported that cryopreservation of NK cells results in loss of cell motility and, as a consequence, cytotoxicity which limits the clinical utility of such products. This study assessed the impact of cryopreservation on the recovery and function of PM21-particle expanded NK cells (PM21-NK cells) as well as their antitumor activity in vitro using 2D and 3D cancer models and in vivo in ovarian cancer models, including patient-derived xenografts (PDX). Viable PM21-NK cells were consistently recovered from cryopreservation and overnight rest with a mean recovery of 73 ± 22% (N = 19). Thawed and rested NK cells maintained the expression of activating receptors when compared to expansion-matched fresh NK cells. Cryopreserved NK cells that were thawed and rested showed no decrease in cytotoxicity when co-incubated with tumor cells at varying effector-to-target (NK:T) ratios compared to expansion-matched fresh NK cells. Moreover, no differences in cytotoxicity were observed between expansion-matched cryopreserved and fresh NK cells in 3D models of tumor killing. These were analyzed by kinetic, live-cell imaging assays co-incubating NK cells with tumor spheroids. When exposed to tumor cells, or upon cytokine stimulation, cryopreserved NK cells that were thawed and rested showed no significant differences in surface expression of degranulation marker CD107a or intracellular expression of TNFα and IFNγ. In vivo antitumor activity was also assessed by measuring the extension of survival of SKOV-3-bearing NSG mice treated with fresh vs. cryopreserved NK cells. Cryopreserved NK cells caused a statistically significant survival extension of SKOV-3-bearing NSG mice that was comparable to that observed with fresh NK cells. Additionally, treatment of NSG mice bearing PDX tumor with cryopreserved PM21-NK cells resulted in nearly doubling of survival compared to untreated mice. These data suggest that PM21-NK cells can be cryopreserved and recovered efficiently without appreciable loss of viability or activity while retaining effector function both in vitro and in vivo. These findings support the use of cryopreserved PM21-NK cells as a cancer immunotherapy treatment.

Horses for Courses in the Era of CARs: Advancing CAR T and CAR NK Cell Therapies

The adoptive transfer of allogeneic CAR NK cells holds great promise as an anticancer modality due to the relative ease of manufacturing and genetic modification of NK cells, which translates into affordable pricing. Compared to the pronounced efficacy of CAR T cell therapy in the treatment of B cell malignancies, rigorous clinical and preclinical assessment of the antitumor properties of CAR NK cells has been lagging behind. In this brief review, we summarize the biological features of NK cells that may help define the therapeutic niche of CAR NK cells as well as create more potent NK cell-based anticancer products. In addition, we compare T cells and NK cells as the carriers of CARs using the data of single-cell transcriptomic analysis.

The Clinical Application of Neoantigens in Esophageal Cancer

Esophageal cancer (EC) is a common malignant tumor with poor prognosis, and current treatments for patients with advanced EC remain unsatisfactory. Recently, immunotherapy has been recognized as a new and promising approach for various tumors. EC cells present a high tumor mutation burden and harbor abundant tumor antigens, including tumor-associated antigens and tumor-specific antigens. The latter, also referred to as neoantigens, are immunogenic mutated peptides presented by major histocompatibility complex class I molecules. While current genomics and bioinformatics technologies have greatly facilitated the identification of tumor neoantigens, identifying individual neoantigens systematically for successful therapies remains a challenging problem. Owing to the initiation of strong, specific tumor-killing cytotoxic T cell responses, neoantigens are emerging as promising targets to develop personalized treatment and have triggered the development of cancer vaccines, adoptive T cell therapies, and combination therapies. This review aims to give a current understanding of the clinical application of neoantigens in EC and provide direction for future investigation.

Fc Receptor is Involved in Nk Cell Functional Anergy Induced by Miapaca2 Tumor Cell Line

Impaired NK cytotoxicity has been linked to poor cancer prognosis, but its mechanisms are not clearly established. Increasing data demonstrate that NK cells lose cytotoxicity after interaction with NK cell-sensitive tumor cells. In this paper, we provide evidence that the human adenocarcinoma cell line MiaPaCa2 and TNFα and TGFβ-treated MiaPaCa2 cultures (MiaPaCa2-TT) induced functional anergy of NK cells via FGL2 protein. MiaPaCa2-TT cultures decreased expression of IFNγ, CD107a, DNAM-1, and stimulated expression of PD1 by NK cells, as well as inhibited their cytotoxic activity in a greater manner compared to the parental culture. More importantly, we found that co-cultivation with anergized NK cells decreased expression of IFNγ and CD107a by naïve NK cells, which supports the hypothesis of NK cell functional anergy transmission. The obtained results suggest a mechanism by which tumor cells may inhibit cytotoxic functions of tumor-infiltrating and circulating NK cells in cancer.

ABBREVIATIONS

CFSE: Carboxyfluorescein diacetate succinimidyl ester; CSCs: Cancer stem cells; FGL2: Fibrinogen-like protein 2; mAbs: Monoclonal antibodies; MiaPaCa2: Human adenocarcinoma cell line; MiaPaCa2-ТТ: Adenocarcinoma cell line MiaPaCa2 cells stimulated with TNFα and TGFβ-1; PI: Propidium iodide; TGFβ: Transforming growth factor beta; TME: Tumor microenvironment; TNFα: Tumor necrosis factor alfa.

Analysis of ex vivo expanded and activated clinical-grade human NK cells after cryopreservation

BACKGROUND AIMS

Several methods to expand and activate (EA) NK cells ex vivo have been developed for the treatment of relapsed or refractory cancers. Infusion of fresh NK cells is generally preferred to the infusion of cryopreserved/thawed (C/T) NK cells because of concern that cryopreservation diminishes NK cell activity. However, there has been little head-to-head comparison of the functionality of fresh versus C/T NK cell products.

METHODS

We evaluated activity of fresh and C/T EA NK cells generated by interleukin (IL)-15, IL-2 and CD137L expansion.

RESULTS

Analysis of C/T NK cell products demonstrated decreased recovery of viable CD56⁺ cells, but the proportion of NK cells in the C/T EA NK cell product did not decrease compared with the fresh EA NK cell product. Fresh and C/T EA NK cells demonstrated increased granzyme B compared with NK cells pre-expansion, but only fresh EA NK cells showed increased NKG2D. Compared with fresh EA NK cells, cytotoxic ability of C/T EA NK cells was reduced, but C/T EA NK cells remained potently cytotoxic against tumor cells via both antibody-independent and antibody-dependent mechanisms within 4 h post-thaw. Fresh EA NK cells generated high levels of gamma interferon (IFN-γ), which was abrogated by JAK1/JAK2 inhibition with ruxolitinib, but C/T EA NK cells showed lower IFN-γ unaffected by JAK1/JAK2 inhibition.

DISCUSSION

Usage of C/T EA NK cells may be an option to provide serial "boost" NK cell infusions from a single apheresis to maximize NK cell persistence and potentially improve NK-induced responses to refractory cancer.