Altered NKp30, NKp46, NKG2D, and DNAM-1 Expression on Circulating NK Cells Is Associated with Tumor Progression in Human Gastric Cancer

Abstract

Natural killer (NK) cell activity is influenced by a complex integration of signaling pathways activated downstream of both activating and inhibitory surface receptors. The tumor microenvironment can suppress NK cell activity, and there is a great clinical interest in understanding whether modulating tumor-mediated NK cell suppression and/or boosting preexisting NK cell numbers in cancer patients is therapeutically viable. To this light, we characterized the surface receptor phenotypes of peripheral blood NK cells and examined their clinical relevance to human gastric cancer (GC). We found that the proportion of peripheral blood NK cells which expressed the activating receptors NKp30, NKp46, NKG2D, and DNAM-1 was significantly decreased in GC patients compared to healthy donors, and that this decrease was positively associated with tumor progression. At the same time, plasma TGF-β1 concentrations were significantly increased in GC patients and negatively correlated with the proportion of NKp30, NKp46, NKG2D, and DNAM-1 expressing NK cells. Furthermore, TGF-β1 significantly downregulated the expression of NKp30, NKp46, NKG2D, and DNAM-1 on NK cells in vitro, and the addition of galunisertib, an inhibitor of the TGF-β receptor subunit I, reversed this downregulation. Altogether, our data suggest that the decreased expression of activating receptors NKp30, NKp46, NKG2D, and DNAM-1 on peripheral blood NK cells is positively associated with GC progression, and that TGF-β1-mediated NK cell suppression may be a therapeutically targetable characteristic of GC.

A Comprehensive Assessment of Human Natural Killer Cell Phenotype and Function in Whole Blood

“…As a possible solution, we present methodologies for parallel assessment of immune cell receptor expression, signaling protein activity, and cytokine production in whole blood-derived NK cells. We have demonstrated the feasibility of these assays through the detection of target protein expression in both healthy and disease states (namely solid malignancies), the reproducibility of these assays in patient cohorts despite inherent inter-patient heterogeneity, and the validity of these assays in that our results are comparable to those previously described in the literature (2,12,32,(34)(35)(36)(37)(38)(39). They are simple, timeefficient, and allow for the assessment of any peripheral immune cell population using a minimal volume of whole blood.…”

New avenues for melanoma immunotherapy: Natural Killer cells?

“…83 In patients affected by digestive cancers and lung adenocarcinoma, tumour progression and survival have been negatively associated with a high expression of inhibitory receptors on NK cells, particularly PD-1 and Tim-3, and with the downregulation of several activating receptors, the latter phenomenon correlating also with TGF-β serum levels and tumour differentiation grade. [84][85][86][87] Conversely, in these patients, survival was positively associated with NKp46 expression. 88 On the other hand, the presence in the blood of mature cytotoxic CD57 + NK cells usually correlate with a lesser severe disease and a better outcome in several clinical settings, even if in some tumours they inversely correlate with the number of infiltrating NK cells and have been associated with therapy resistance.…”

“…Notably, alterations in circulating NK cells frequency, phenotype and function have also been found in tumour patients and have been associated with the clinical outcome . So far, the analysis of peripheral blood NK cells in solid tumours patients showed an association between a suppressed functionally impaired NK cells phenotype and poor prognosis.…”

“…In patients affected by digestive cancers and lung adenocarcinoma, tumour progression and survival have been negatively associated with a high expression of inhibitory receptors on NK cells, particularly PD‐1 and Tim‐3, and with the downregulation of several activating receptors, the latter phenomenon correlating also with TGF‐β serum levels and tumour differentiation grade . Conversely, in these patients, survival was positively associated with NKp46 expression …”

“…80 Notably, alterations in circulating NK cells frequency, phenotype and function have also been found in tumour patients and have been associated with the clinical outcome. [81][82][83][84][85][86][87][88][89][90] So far, the analysis of peripheral blood NK cells in solid tumours patients showed an association between a suppressed functionally impaired NK cells phenotype and poor prognosis. Peripheral NK cells from metastatic melanoma patients show an exhausted phenotype, with a high expression of KIRs, low levels of NCRs and downregulation of stimulating cytokines receptors, that result in functional defects in their ability to proliferate, secrete cytokines and kill target cells.…”