Fractalkine Elicits Chemotactic, Phenotypic, and Functional Effects on CX3CR1+CD27- NK Cells in Obesity-Associated Cancer

Harnessing the Power of NK Cell Receptor Engineering as a New Prospect in Cancer Immunotherapy

Natural killer (NK) cells have recently gained popularity as an alternative for cancer immunotherapy. Adoptive cell transfer employing NK cells offers a safer therapeutic option compared to T-cell-based therapies, due to their significantly lower toxicity and the availability of diverse autologous and allogeneic NK cell sources. However, several challenges are associated with NK cell therapies, including limited in vivo persistence, the immunosuppressive and hostile tumor microenvironment (TME), and the lack of effective treatments for solid tumors. To address these limitations, the modification of NK cells to stably produce cytokines has been proposed as a strategy to enhance their persistence and proliferation. Additionally, the overexpression of activating receptors and the blockade of inhibitory receptors can restore the NK cell functions hindered by the TME. To further improve tumor infiltration and the elimination of solid tumors, innovative approaches focusing on the enhancement of NK cell chemotaxis through the overexpression of chemotactic receptors have been introduced. This review highlights the latest advancements in preclinical and clinical studies investigating the engineering of activating, inhibitory, and chemotactic NK cell receptors; discusses recent progress in cytokine manipulation; and explores the potential of combining the chimeric antigen receptor (CAR) technology with NK cell receptors engineering.

Analysing the Combined Effects of Radiotherapy and Chemokine Receptor 5 Antagonism: Complementary Approaches to Promote T Cell Function and Migration in Oesophageal Adenocarcinoma

The presence of an immunosuppressive tumour microenvironment in oesophageal adenocarcinoma (OAC) is a major contributor to poor responses. Novel treatment strategies are required to supplement current regimens and improve patient survival. This study examined the immunomodulatory effects that radiation therapy and chemokine receptor antagonism impose on T cell phenotypes in OAC with a primary goal of identifying potential therapeutic targets to combine with radiation to improve anti-tumour responses. Compared with healthy controls, anti-tumour T cell function was impaired in OAC patients, demonstrated by lower IFN-γ production by CD4+ T helper cells and lower CD8+ T cell cytotoxic potential. Such diminished T cell effector functions were enhanced following treatment with clinically relevant doses of irradiation. Interestingly, CCR5+ T cells were significantly more abundant in OAC patient blood compared with healthy controls, and CCR5 surface expression by T cells was further enhanced by clinically relevant doses of irradiation. Moreover, irradiation enhanced T cell migration towards OAC patient-derived tumour-conditioned media (TCM). In vitro treatment with the CCR5 antagonist Maraviroc enhanced IFN-γ production by CD4+ T cells and increased the migration of irradiated CD8+ T cells towards irradiated TCM, suggesting its synergistic therapeutic potential in combination with irradiation. Overall, this study highlights the immunostimulatory properties of radiation in promoting anti-tumour T cell responses in OAC and increasing T cell migration towards chemotactic cues in the tumour. Importantly, the CCR5 antagonist Maraviroc holds promise to be repurposed in combination with radiotherapy to promote anti-tumour T cell responses in OAC.

Real-time ex vivo monitoring of NK cell migration toward obesity-associated oesophageal adenocarcinoma following modulation of CX3CR1

Oesophagogastric adenocarcinomas (OAC) are poor prognosis, obesity-associated cancers which may benefit from natural killer (NK) cell-based immunotherapies. Cellular immunotherapies encounter two key challenges to their success in OAC, namely recruitment to extratumoural tissues such as the omentum at the expense of the tumour and an immunosuppressive tumour microenvironment (TME) which can hamper NK cell function. Herein, we examined approaches to overcome the detrimental impact of obesity on NK cells and NK cell-based immunotherapies. We have demonstrated that NK cells migrate preferentially to the chemotactic signals of OAC patient-derived omentum over tumour in an ex vivo model of immune cell migration. We have identified CX3CR1 modulation and/or tumour chemokine profile remodelling as approaches to skew NK cell migration towards tumour. We also report targetable immunosuppressive facets of the obese OAC TME which dampen NK cell function, in particular cytotoxic capabilities. These data provide insights into approaches to therapeutically overcome key challenges presented by obesity and will inform superior design of NK cell-based immunotherapies for OAC.

Tumour microenvironment influences response to treatment in oesophageal adenocarcinoma

The poor treatment response of oesophageal adenocarcinoma (OAC) leads to low survival rates. Its increasing incidence makes finding more effective treatment a priority. Recent treatment improvements can be attributed to the inclusion of the tumour microenvironment (TME) and immune infiltrates in treatment decisions. OAC TME is largely immunosuppressed and reflects treatment resistance as patients with inflamed TME have better outcomes. Priming the tumour with the appropriate neoadjuvant chemoradiotherapy treatment could lead to higher immune infiltrations and higher expression of immune checkpoints, such as PD-1/PDL-1, CTLA4 or emerging new targets: LAG-3, TIM-3, TIGIT or ICOS. Multiple trials support the addition of immune checkpoint inhibitors to the current standard of care. However, results vary, supporting the need for better response biomarkers based on TME composition. This review explores what is known about OAC TME, the clinical significance of the various cell populations infiltrating it and the emerging therapeutical combination with a focus on immune checkpoints inhibitors.

Measuring Immune Cell Movement Toward the Soluble Microenvironment of Human Tissues Using a Boyden Chamber-Based Migration Assay

Migration assays are used to measure cell movement toward a variety of chemoattractants in a controlled environment. Here we describe a method for a Boyden chamber-based migration assay using conditioned media generated from the tumor, liver, and visceral adipose tissue of cancer patients.

Investigating the susceptibility of treatment-resistant oesophageal tumours to natural killer cell-mediated responses

The majority of oesophageal adenocarcinoma (OAC) patients do not respond to multimodal treatment regimens and face dismal survival rates. Natural killer (NK) cells are crucial anti-tumour immune cells, and this study investigated the susceptibility of treatment-resistant OAC cells to these potent tumour killers. Natural killer receptor (NKR) ligand expression by OE33CisP (cisplatin-sensitive) and OE33CisR (cisplatin-resistant) cells was investigated. The immunomodulatory effects of OE33CisP and OE33CisR cells on NK cell phenotype and function were assessed. Finally, the impact of chemotherapy regimens on NKR ligand shedding was examined. Our data revealed significantly less surface expression of activating ligands B7-H6, MICA/B, ULBP-3 and activating/inhibitory ligands PVRL-1 and PVRL-4 by OE33CisR cells, compared to OE33CisP cells. Co-culture with OE33CisR cells reduced the frequencies of NKp30⁺ and NKp46⁺ NK cells and increased frequencies of TIGIT⁺, FasL⁺ and TRAIL⁺ NK cells. Frequencies of IFN-γ-producing NK cells increased while frequencies of TIM-3⁺ NK cells decreased after culture with OE33CisP and OE33CisR cells. Frequencies of circulating NKp30⁺ NK cells were significantly lower in OAC patients with the poorest treatment response and in patients who received FLOT chemotherapy, while B7-H6 shedding by OAC tumour cells was induced by FLOT. Overall, OE33CisR cells express less activating NKR ligands than OE33CisP cells and have differential effects on NKR expression by NK cells. However, neither cell line significantly dampened NK cell cytokine production, death receptor expression or degranulation. In addition, our data indicate that FLOT chemotherapy may promote B7-H6 shedding and immune evasion with detrimental consequences in OAC patients.

Natural killer cell therapy: A new frontier for obesity-associated cancer

Natural killer (NK) cell infiltration of solid tumours is associated with better outcomes, placing augmentation of NK cell abundance in tumours as an attractive immunotherapeutic approach. The unique ability of NK cells to target cancer cells without antigen specificity increases their versatility and applicability as an immunotherapeutic tool. However, successful utilisation of NK cell-based therapies in solid tumours is still at an early stage. Obesity has become a global health epidemic, and the prevalence of obesity-associated cancers has significantly increased. Obesity-associated malignancies provide a unique challenge for the successful application of cell-based immunotherapies including NK cell-based therapies because significant numbers of NK and T cells are recruited to the visceral adipose tissue at the expense of successful tumour infiltration and eradication. As such, immunotherapy efficacy has been disappointing for obesity-associated malignancies such as oesophageal and gastric adenocarcinoma. Therefore, immunotherapies for obesity-associated cancers warrant our further attention. Indeed, it is becoming ever more obvious that more innovative approaches are needed to re-invigorate anti-tumour immunity and overcome immune exclusion in such tumours. In this review, we briefly summarise the dysfunctionality of NK cells in obesity-associated cancer. We outline the NK cell-based immunotherapeutic approaches which hold promise as effective treatments in this disease space, including CAR-NK cells. Furthermore, we suggest future avenues which possess the potential to transform immunotherapy and specifically NK cell therapy efficacy for obesity-associated cancer.

The Omentum in Obesity-Associated Cancer: A Hindrance to Effective Natural Killer Cell Migration towards Tumour Which Can Be Overcome by CX3CR1 Antagonism

Simple Summary

Oesophagogastric adenocarcinomas (OAC) are cancers of the food pipe and stomach which have a strong link with obesity. Natural killer (NK) cells are assassins of the immune system and are crucial for eliminating cancer. We have shown previously that NK cells are pulled into fat in OAC patients by a signalling protein called fractalkine (CX3CL1). Once in fat, NK cells die or are profoundly altered. This diminishes their ability to kill the tumour. We report that exposure to fat can reduce movement of NK cells towards the tumour. However, if a drug called a CX3CR1 antagonist is used to antagonise the receptor for fractalkine, we can restore NK cell movement towards the tumour. When we activate NK cells with a protein called IL-15, fractalkine can reduce its effect on NK cells. This provides further evidence for using CX3CR1 antagonists to reduce NK cell migration to fat and boost NK cell movement to the tumour.

Abstract

Oesophagogastric adenocarcinomas (OAC) are obesity-associated malignancies, underpinned by severe immune dysregulation. We have previously shown that natural killer (NK) cells preferentially migrate to OAC omentum, where they undergo phenotypic and functional alterations and apoptosis. Furthermore, we have identified the CX3CR1:fractalkine (CX3CL1) pathway as pivotal in their recruitment to omentum. Here, we elucidate whether exposure to the soluble microenvironment of OAC omentum, and in particular fractalkine and IL-15 affects NK cell homing capacity towards oesophageal tumour. Our data uncover diminished NK cell migration towards OAC tumour tissue conditioned media (TCM) following exposure to omental adipose tissue conditioned media (ACM) and reveal that this migration can be rescued with CX3CR1 antagonist E6130. Furthermore, we show that fractalkine has opposing effects on NK cell migration towards TCM, when used alone or in combination with IL-15 and uncover its inhibitory effects on IL-15-mediated stimulation of death receptor ligand expression. Interestingly, treatment with fractalkine and/or IL-15 do not significantly affect NK cell adhesion to MAdCAM-1, despite changes they elicit to the expression of integrin α4β7. This study provides further evidence that CX3CR1 antagonism has therapeutic utility in rescuing NK cells from the deleterious effects of the omentum and fractalkine in OAC, thus limiting their dysfunction.