Esther Duran

Human NK cells in acute myeloid leukaemia patients: analysis of NK cell-activating receptors and their ligands

Natural killer (NK) cell activation is strictly regulated to ensure that healthy cells are preserved, but tumour-transformed or virus-infected cells are recognized and eliminated. To carry out this selective killing, NK cells have an ample repertoire of receptors on their surface. Signalling by inhibitory and activating receptors by interaction with their ligands will determine whether the NK cell becomes activated and kills the target cell. Here, we show reduced expression of NKp46, NKp30, DNAM-1, CD244 and CD94/NKG2C activating receptors on NK cells from acute myeloid leukaemia patients. This reduction may be induced by chronic exposure to their ligands on leukaemic blasts. The analysis of ligands for NK cell-activating receptors showed that leukaemic blasts from the majority of patients express ligands for NK cell-activating receptors. DNAM-1 ligands are frequently expressed on blasts, whereas the expression of the NKG2D ligand MICA/B is found in half of the patients and CD48, a ligand for CD244, in only one-fourth of the patients. The decreased expression of NK cell-activating receptors and/or the heterogeneous expression of ligands for major receptors on leukaemic blasts can lead to an inadequate tumour immunosurveillance by NK cells. A better knowledge of the activating receptor repertoire on NK cells and their putative ligands on blasts together with the possibility to modulate their expression will open new possibilities for the use of NK cells in immunotherapy against leukaemia.

Expression of adhesion molecules and ligands for activating and costimulatory receptors involved in cell-mediated cytotoxicity in a large panel of human melanoma cell lines

Knowledge of the interactions between MHC-unrestricted cytotoxic effector cells and solid tumour cells is essential for introducing more effective NK cell-based immunotherapy protocols into clinical practise. Here, to begin to obtain an overview of the possible universe of molecules that could be involved in the interactions between immune effector cells and melanoma, we analyse the surface expression of adhesion and costimulatory molecules and of ligands for NK-activating receptors on a large panel of cell lines from the “European Searchable Tumour Cell Line and Data Bank” (ESTDAB, http://www.ebi.ac.uk/ipd/estdab/) and discuss their potential role in the immune response against this tumour. We show that most melanoma cell lines express not only adhesion molecules that are likely to favour their interaction with cells of the immune system, but also their interaction with endothelial cells potentially increasing their invasiveness and metastatic capacity. A high percentage of melanoma cell lines also express ligands for the NK-activating receptor NKG2D; whereas, the majority express MICA/B molecules, ULBP expression, however, was rarely found. In addition to these molecules, we also found that CD155 (poliovirus receptor, PVR) is expressed by the majority of melanoma cell lines, whereas CD112 (Nectin-2) expression was rare. These molecules are DNAM-1 ligands, a costimulatory molecule involved in NK cell-mediated cytotoxicity and cytokine production that also mediates costimulatory signals for triggering naïve T cell differentiation. The phenotypical characterisation of adhesion molecules and ligands for receptors involved in cell cytotoxicity on a large series of melanoma cell lines will contribute to the identification of markers useful for the development of new immunotherapy strategies.

Lymphocyte activation in response to melanoma: interaction of NK-associated receptors and their ligands

In recent years, studies on the molecular and cellular mechanisms of immune responses against melanoma have contributed to a better understanding of how these tumours can be recognised by cytotoxic cells and the mechanisms they have developed to escape from innate and adaptive immunity. Lysis of melanoma cells by natural killer (NK) cells and cytolytic T cells is the result of a fine balance between signals transmitted by activating and inhibitory receptors. In addition to the T cell receptor, these were initially described as NK cell-associated receptors (NKRs) and were later also found on subsets of T lymphocytes, particularly effector-memory and terminally differentiated CD8 T cells. An increase of NKR+CD8+ T cells has been found in melanoma patients, correlating with the expansion of differentiated effector CD8+CD28null CD27null T cells. NKRs can regulate the lysis of target cells expressing appropriate ligands. Activating receptors recognise ligands on tumours whereas inhibitory receptors are specific for MHC class I antigens and sense missing self. Altered expression of MHC class I antigens is frequently found on melanoma cells, preventing recognition by specific cytolytic T cells but favouring NK cell recognition. Changes in the expression of NKR-ligands in melanoma contribute in explaining the differences in the capacity of cytotoxic immune cells to control melanoma growth and dissemination.

NK cell recognition and killing of melanoma cells is controlled by multiple activating receptor-ligand interactions.

The role of natural killer (NK) cells in tumor immunosurveillance has been recently underlined. A better understanding of the receptor-ligand interactions between NK cells and solid tumor cells is essential for introducing more effective NK cell-based immunotherapy protocols into clinical practice. We previously analyzed the surface expression of ligands for NK cell-activating receptors and costimulatory molecules in a large panel of melanoma cell lines. Although the expression of ligands for NK cell-activating receptors is variable, the majority of melanoma cell lines express ligands for NKG2D and for DNAX accessory molecule-1 (DNAM-1). While the NKG2D receptor has been described as the principal entity responsible for the lysis of several melanoma cell lines, the role of natural cytotoxicity receptors (NCRs) and DNAM-1 receptors in NK cell recognition and killing of melanoma cells has been recently emphasized. Antibody-mediated masking of NKG2D, NCRs, and DNAM-1 has proven that NKG2D, NCRs, and DNAM-1 frequently cooperate in the lysis of melanoma cells. In this work, we provide an overview of recent advances in the study of melanoma cells’ susceptibility to NK cell-mediated lysis and how multiple receptor-ligand interactions participate in melanoma cell elimination.

Natural killer cell immunosenescence in acute myeloid leukaemia patients: new targets for immunotherapeutic strategies?

Several age-associated changes in natural killer (NK) cell phenotype have been reported that contribute to the defective NK cell response observed in elderly patients. A remodelling of the NK cell compartment occurs in the elderly with a reduction in the output of immature CD56bright cells and an accumulation of highly differentiated CD56dim NK cells. Acute myeloid leukaemia (AML) is generally a disease of older adults. NK cells in AML patients show diminished expression of several activating receptors that contribute to impaired NK cell function and, in consequence, to AML blast escape from NK cell immunosurveillance. In AML patients, phenotypic changes in NK cells have been correlated with disease progression and survival. NK cell-based immunotherapy has emerged as a possibility for the treatment of AML patients. The understanding of age-associated alterations in NK cells is therefore necessary to define adequate therapeutic strategies in older AML patients.

Evaluation of the duration of ureteral stenting following endopyelotomy: Animal study

Background: The purpose of the present paper was to evaluate whether it is possible to reduce the duration of ureteral stenting following endopyelotomy, and thus reduce side‐effects.

Immunosenescence: limitations of natural killer cell-based cancer immunotherapy

Cancer is primarily considered a disease of old age. Immunosenescence refers to the age-associated changes in the immune system, and its contribution to the increased risk of cancer in old individuals has been discussed for many years. Natural killer (NK) cells are cytotoxic innate immune cells specialized in defence against tumour and virus-infected cells. NK cell cytotoxicity is the result of a fine balance between activating and inhibitory receptors. Several activating receptors have been identified that recognize different ligands frequently found over-expressed on tumour cells or virus-infected cells. The most important NK cell inhibitory receptors interact with major histocompatibility complex class I molecules expressed on almost all nucleated cells preventing NK cell-mediated lysis of healthy cells. NK cell immunosenescence is characterized by a redistribution of NK cell subsets, a diminished expression of several activating receptors and lower per-cell cytotoxicity. Altered expression of activating receptors has also been described in young and elderly cancer patients probably due to chronic exposure to ligands on tumour cells. Thus, the effect of both age and cancer may act synergistically to diminish NK cell-mediated tumour immunosurveillance. Different strategies harnessing the power of NK cells to target tumour cells have been designed including adoptive therapy with autologous or allogeneic expanded NK cells. In addition, checkpoint blockade of inhibitory receptors and the use of agonist antibodies to stimulate activating receptors are emerging areas of research. In this context, the effect of immunosenescence should be considered to improve the efficiency of cancer immunotherapy.

Natural Killer Cell Recognition of Melanoma: New Clues for a More Effective Immunotherapy

Natural killer (NK) cells participate in the early immune response against melanoma and also contribute to the development of an adequate adaptive immune response by their crosstalk with dendritic cells and cytokine secretion. Melanoma resistance to conventional therapies together with its high immunogenicity justifies the development of novel therapies aimed to stimulate effective immune responses against melanoma. However, melanoma cells frequently escape to CD8 T cell recognition by the down-regulation of major histocompatibility complex (MHC) class I molecules. In this scenario, NK cells emerge as potential candidates for melanoma immunotherapy due to their capacity to recognize and destroy melanoma cells expressing low levels of MHC class I molecules. In addition, the possibility to combine immune checkpoint blockade with other NK cell potentiating strategies (e.g., cytokine induction of activating receptors) has opened new perspectives in the potential use of adoptive NK cell-based immunotherapy in melanoma.

Correlation of effector function with phenotype and cell division after in vitro differentiation of naive MART-1-specific CD8+ T cells.

Adoptive transfer of antigen-specific CD8+ T cells may represent an effective strategy for immunotherapy of tumors such as melanoma, but is limited by the number and functionality of in vitro expanded T cells. Here, we document that although ELAGIGILTV-specific CD8+ T cells from different donors initially possessed a naive phenotype, after antigen-induced in vitro expansion two distinct phenotypes correlating with cell proliferation rate emerged in the different donors. Those cultures achieving fewer cumulative population doublings (CPDs) were cytotoxic and displayed a CD45RA+CCR7- phenotype. In contrast, cultures reaching higher CPDs were non-cytotoxic T cells with a CD45RA-CCR7- phenotype. Thus, the generation of larger numbers of ELAGIGILTV-specific CD8+ T cells correlates negatively with the acquisition of a CD45RA+CCR7- phenotype and cytotoxic capacity. A better understanding of the differentiation pathways of cytotoxic T cells to obtain optimally efficient cells for adoptive transfer will allow the development of new immunotherapy protocols.

Angiographic study and therapeutic embolization of soft-tissue fibrosarcoma in a dog: case report and literature.

A case of soft-tissue fibrosarcoma with pulmonary metastases in a dog is reported. Although three attempts of fine-needle aspiration (FNA) biopsy failed to provide definitive tumor diagnosis, results of angiography strongly indicated a soft-tissue sarcoma. Transcatheter arterial embolization (TAE) using particles of gelatin sponge was performed following selective angiography. The mass was decreased in size on reevaluation 2 weeks after embolization. The dog was euthanized on the request of the owners due to overall failing health. Necropsy and pathological study confirmed the diagnosis of soft-tissue fibrosarcoma with pulmonary metastases. In a review of the literature, angiographic findings of soft-tissue sarcoma in the dog of this report were similar to those in human beings, suggesting a potential role for angiography in the differential diagnosis of suspect soft-tissue fibrosarcomas and for guiding FNA or surgical biopsy. Previous reports have also shown therapeutic embolization to be an effective treatment both in experimental animal study and in clinical practice in the human; therefore, TAE could be an effective adjunctive treatment of soft-tissue fibrosarcoma in the dog.