IL-1R8 silencing improves the anti-tumor function of freshly isolated human NK cells

TLR2/4 are novel activating receptors for SARS-CoV-2 spike protein on NK cells

Background

In early infected or severe coronavirus disease 2019 (COVID-19) patients, circulating NK cells are consistently reduced, despite being highly activated or exhausted. The aim of this paper was to establish whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein (SP) may directly trigger NK cells and through which receptor(s).

Methods

SP-stimulated human NK cells have been evaluated for the expression of activation markers, cytokine release, and cytotoxic activity, as well as for gene expression profiles and NF-kB phosphorylation, and they have been silenced with specific small interfering RNAs.

Results

SPs from the Wuhan strain and other variants of concern (VOCs) directly bind and stimulate purified NK cells by increasing activation marker expression, cytokine release, and cytolytic activity, prevalently in the CD56brightNK cell subset. VOC-SPs differ in their ability to activate NK cells, G614, and Delta-Plus strains providing the strongest activity in the majority of donors. While VOC-SPs do not trigger ACE2, which is not expressed on NK cells, or other activating receptors, they directly and variably bind to both Toll-like receptor 2 (TLR2) and TLR4. Moreover, SP-driven NK cell functions are inhibited upon masking such receptors or silencing the relative genes. Lastly, VOC-SPs upregulate CD56dimNK cell functions in COVID-19 recovered, but not in non-infected, individuals.

Conclusions

TLR2 and TLR4 are novel activating receptors for SP in NK cells, suggesting a new role of these cells in orchestrating the pathophysiology of SARS-CoV-2 infection. The pathogenic relevance of this finding is highlighted by the fact that free SP providing NK cell activation is frequently detected in a SARS-CoV-2 inflamed environment and in plasma of infected and long-COVID-19 subjects.

Immune checkpoint molecule DNAM-1/CD112 axis is a novel target for natural killer-cell therapy in acute myeloid leukemia

Acute myeloid leukemia (AML) is a hematologic malignancy that frequently relapses, even if remission can be achieved with intensive chemotherapy. One known relapse mechanism is the escape of leukemic cells from immune surveillance. Currently, there is no effective immunotherapy for AML because of the lack of specific antigens. Here, we aimed to elucidate the association between CD155 and CD112 in AML cell lines and primary AML samples and determine the therapeutic response. Briefly, we generated NK-92 cell lines (NK-92) with modified DNAX-associated molecule 1 (DNAM-1) and T-cell immunoglobulin and ITIM domain (TIGIT), which are receptors of CD155 and CD112, respectively. Analysis of 200 cases of AML indicated that the survival of patients with high expression of CD112 was shorter than that of patients with low expression. NK-92 DNAM-1 exhibited enhanced cytotoxic activity against AML cell lines and primary cells derived from patients with AML. DNAM-1 induction in NK-92 cells enhanced the expression of cytotoxicity-related genes, thus overcoming the inhibitory activity of TIGIT. Between CD155 and CD112, CD112 is an especially important target for natural killer (NK)-cell therapy of AML. Using a xenograft model, we confirmed the enhanced antitumor effect of NK-92 DNAM-1 compared with that of NK-92 alone. We also discovered that CD112 (Nectin-2), an immune checkpoint molecule belonging to the Nectin/Nectin-like family, functions as a novel target of immunotherapy. In conclusion, modification of the DNAM-1/CD112 axis in NK cells may be an effective novel immunotherapy for AML. Furthermore, our findings suggest that the levels of expression of these molecules are potential prognostic markers in AML.

The anti-inflammatory cytokine IL-37 improves the NK cell-mediated anti-tumor response

IL-37 is a member of the IL-1 superfamily exerting anti-inflammatory functions in a number of diseases. Extracellular IL-37 triggers the inhibitory receptor IL-1R8 that is known to regulate different NK cell pathways and functional activities including their anti-tumor effect. However, the effect of IL-37 on human NK cell functions is still to be unveiled. This study aimed to investigate the functional effect of IL-37 in human NK cells activated with IL-15. We found that IL-37 enhanced both NK cell cytotoxic activity against different tumor cell lines and cytokines production. These effects were associated with increased phosphorylation of ERK and NF-Kb. The improved NK cell activity was also strictly related to a time-dependent GSK3β-mediated degradation of IL-1R8. The enhanced activation profile of IL-37 treated NK cells possibly due to IL-1R8 degradation was confirmed by the results with IL-1R8-silenced NK cells. Lastly, in line with these data, through the analysis of the TNM plot database of a large group of patients, IL-37 mRNA expression was found to be significantly lower in colon and skin cancers than in normal tissues. Colon adenocarcinoma and neuroblastoma patients with higher IL-37 mRNA levels had significantly higher overall survival, suggesting that the presence of IL-37 might be considered an independent positive prognostic factor for this tumor. Our results provide novel information on the mechanisms regulating IL-1R8 function in human NK cells, highlighting the IL-37-IL-1R8 axis as a potential new target to improve the anti-tumor immune response.

IL-1R8: A molecular brake of anti-tumor and anti-viral activity of NK cells and ILC

Interleukin-1 receptor family members (ILRs) and Toll-Like Receptors (TLRs) play pivotal role in immunity and inflammation and are expressed by most cell types including cells of both the innate and adaptive immune system. In this context, IL-1 superfamily members are also important players in regulating function and differentiation of adaptive and innate lymphoid cells. This system is tightly regulated in order to avoid uncontrolled activation, which may lead to detrimental inflammation contributing to autoimmune or allergic responses. IL-1R8 (also known as TIR8 or SIGIRR) is a member of the IL-1R family that acts as a negative regulator dampening ILR and TLR signaling and as a co-receptor for human IL-37. Human and mouse NK cells, that are key players in immune surveillance of tumors and infections, express high level of IL-1R8. In this review, we will summarize our current understanding on the structure, expression and function of IL-1R8 and we will also discuss the emerging role of IL-1R8 as an important checkpoint regulating NK cells function in pathological conditions including cancer and viral infections.

Focusing on NK cells and ADCC: A promising immunotherapy approach in targeted therapy for HER2-positive breast cancer

Human epidermal growth factor receptor 2 (HER2)-positive breast cancer has a high metastatic potential. Monoclonal antibodies (mAbs) that target HER2, such as trastuzumab and pertuzumab, are the cornerstone of adjuvant therapy for HER2-positive breast cancer. A growing body of preclinical and clinical evidence points to the importance of innate immunity mediated by antibody-dependent cellular cytotoxicity (ADCC) in the clinical effect of mAbs on the resulting anti-tumor response. In this review, we provide an overview of the role of natural killer (NK) cells and ADCC in targeted therapy of HER2-positive breast cancer, including the biological functions of NK cells and the role of NK cells and ADCC in anti-HER2 targeted drugs. We then discuss regulatory mechanisms and recent strategies to leverage our knowledge of NK cells and ADCC as an immunotherapy approach for HER2-positive breast cancer.