Extracellular NK histones promote immune cell anti-tumor activity by inducing cell clusters through binding to CD138 receptor

Abstract

BackgroundNatural killer (NK) cells are important anti-tumor cells of our innate immune system. Their anti-cancer activity is mediated through interaction of a wide array of activating and inhibitory receptors with their ligands on tumor cells. After activation, NK cells also secrete a variety of pro-inflammatory molecules that contribute to the final immune response by modulating other innate and adaptive immune cells. In this regard, external proteins from NK cell secretome and the mechanisms by which they mediate these responses are poorly defined.MethodsTRANS-stable-isotope labeling of amino acids in cell culture (TRANS-SILAC) combined with proteomic was undertaken to identify early materials transferred between cord blood-derived NK cells (CB-NK) and multiple myeloma (MM) cells. Further in vitro and in vivo studies with knock-down of histones and CD138, overexpression of histones and addition of exogenous histones were undertaken to confirm TRANS-SILAC results and to determine functional roles of this material transferred.ResultsWe describe a novel mechanism by which histones are actively released by NK cells early after contact with MM cells. We show that extracellular histones bind to the heparan sulfate proteoglycan CD138 on the surface of MM cells to promote the creation of immune-tumor cell clusters bringing immune and MM cells into close proximity, and thus facilitating not only NK but also T lymphocyte anti-MM activity.ConclusionThis study demonstrates a novel immunoregulatory role of NK cells against MM cells mediated by histones, and an additional role of NK cells modulating T lymphocytes activity that will open up new avenues to design future immunotherapy clinical strategies.

Natural Killer Cells in Immunotherapy: Are We Nearly There?

“…Another crucial immunoregulatory role of NK cells for T cells has been observed by us in the context of tumor cells, but in this case, NK cells stimulate T cell activity. We found that NK cells, by releasing pro-inflammatory molecules, such as histones, promote the anti-tumor activity of T cells by accelerating T cell/tumor cell cluster formation [106]. All these studies showing the immunoregulatory role performed between NK cells and T cells should be considered in immunotherapy to find a balance between both immune populations, as both are required to eliminate tumor cells in an efficient manner.…”

“…Of note, we have also observed that CB-NK [11] release histones with anti-fungal in vitro and in vivo activity against Candida albicans (unpublished data). Moreover, this immunomodulatory role for NK cell histones was also observed in a tumor context, where histones released by NK cells were able to recruit T cells to perform anti-tumor activity [106].…”

“…Not only histones but also other pro-inflammatory molecules, such as heat shock proteins, present in neutrophil-derived NETs [131], also participate in the anti-fungal activity of NK cells [139]. In this regard, we also noticed that heat shock proteins are among the pro-inflammatory proteins released by NK cells when they encounter multiple myeloma cells [106]. Studies in fungal infections with NK cells have also demonstrated the important collaboration between all immune cell subsets, a finding that might be considered to create a balance in cancer immunotherapy that does not inhibit the activity of NK cells.…”

“…This can be alleviated by using artificial antigen presenting cells (aAPCs) expressing membrane-bound IL-21 in place of aAPCs that express membrane-bound IL-15 [170], or transduction of the gene encoding the catalytic subunit of human telomerase, hTERT [169]. In cancer, NK cell senescence has not been clearly defined [171], but NK cells do release SASP-like molecules in response to tumor cells, and upregulate KLRG1 and ATM phosphorylation, key senescence markers, in response to chronic stimulation [106,172]. Furthermore, blocking the ATM-dependent DNA damage response pathway during NK cell activation led to enhanced NK cell activity, downregulation of KLRG1, improved persistence, and better tumor clearance in a murine B cell lymphoma model [172].…”

Senescence in the Development and Response to Cancer with Immunotherapy: A Double-Edged Sword

“…Recently, it has been identified that IFNγ and TNFα, two cytokines highly secreted after cell immunotherapy [ 85 ], induce senescence in different murine and human neoplastic diseases [ 86 ]. Moreover, we observed that natural killer (NK) cells, which are used as a source for immunotherapy [ 87 ], secrete a high variety of proinflammatory molecules, including matrix metalloproteases, heat shock proteins [ 88 ] and others present in the SASP.…”