Natural killer cell recognition of in vivo drug-induced senescent multiple myeloma cells

Abstract

Recognition of tumor cells by the immune system is a key step in cancer eradication. Melphalan is an alkylating agent routinely used in the treatment of patients with multiple myeloma (MM), but at therapeutic doses it leads to an immunosuppressive state due to lymphopenia. Here, we used a mouse model of MM to investigate the ability of in vivo treatment with low doses of melphalan to modulate natural killer (NK) cell activity, which have been shown to play a major role in the control of MM growth. Melphalan treatment was able to enhance the surface expression of the stress-induced NKG2D ligands RAE-1 and MULT-1, and of the DNAM-1 ligand PVR (CD155) on MM cells, leading to better tumor cell recognition and killing by NK cells, as highlighted by NK cell increased degranulation triggered by melphalan-treated tumor cells. Remarkably, NK cell population was not affected by the melphalan dose used, but rather displayed activation features as indicated by CD107a and CD69 expression. Furthermore, we showed that low doses of melphalan fail to induce tumor cell apoptosis, but promote the in vivo establishment of a senescent tumor cell population, harboring high levels of the stressinduced ligands RAE-1 and PVR. Taken together our data support the concept of using chemotherapy in order to boost antitumor innate immune responses and report the possibility to induce cellular senescence of tumor cells in vivo.Abbreviations: BM, bone marrow; C 12 FDG, 5-dodecanoylaminofluorescein di-b-D-galactopyranoside; DDR, DNA damage response; DNAM-1, DNAX accessory molecule-1; IMiDs, immunomodulatory drugs; MFI, median fluorescence intensity; MM, multiple myeloma; NK cell, natural killer cell; NKG2D, natural-killer group 2 member D; PBS, phosphate-buffered saline; SA-b-Gal, senescence-associated b-galactosidase; SASP, senescence-associated secretory phenotype; X-Gal, 5-bromo-4-chloro-3-indolyl b-D-galactopyranoside

Senescent cells: Living or dying is a matter of NK cells

“…Similarly, in a mouse model of MM, low doses of melphalan promote the in vivo establishment of a senescent tumor cell population, harboring high levels of the stress‐induced ligands RAE‐1 and PVR . Remarkably, engagement of NKG2D and DNAM‐1 not only targets senescent tumor cells to NK cell‐mediated cytotoxicity, but also triggers NK cell production of IFN‐γ, that in turn can elicit macrophage activity, thus, contributing to the clearance of senescent cells (Fig. ) .…”

“…In this context, multiple myeloma (MM) cell lines and patient‐derived malignant plasma cells treated with sublethal (not apoptotic) doses of chemotherapeutic drugs, namely doxorubicin and melphalan, become senescent with increased cell surface expression of the NKG2D ligands (MICA/B and ULBP1‐3) and DNAM‐1 ligands (PVR and Nectin‐2) . Similarly, in a mouse model of MM, low doses of melphalan promote the in vivo establishment of a senescent tumor cell population, harboring high levels of the stress‐induced ligands RAE‐1 and PVR . Remarkably, engagement of NKG2D and DNAM‐1 not only targets senescent tumor cells to NK cell‐mediated cytotoxicity, but also triggers NK cell production of IFN‐γ, that in turn can elicit macrophage activity, thus, contributing to the clearance of senescent cells (Fig.…”

“…Neutrophils have been also shown to participate in tumor clearance after senescence induction due to p53 reactivation in hepatocarcinoma cells . On the other hand, NK cells have been described to efficiently target senescent hepatic stellate cells, senescent hepatocarcinoma cells after p53 restoration, and drug‐induced senescent multiple myeloma cells . Finally, premalignant N‐RAS‐expressing senescent hepatocytes have been reported to be controlled by a CD4 T lymphocyte‐mediated immune response, that likely then supports macrophages and NK cells .…”

“…34 On the other hand, NK cells have been described to efficiently target senescent hepatic stellate cells, 35,36 senescent hepatocarcinoma cells after p53 restoration, 12,34 and druginduced senescent multiple myeloma cells. 10,37 Finally, premalignant N-RAS-expressing senescent hepatocytes have been reported to be controlled by a CD4 T lymphocyte-mediated immune response, that likely then supports macrophages and NK cells. 33 It is worth mentioning that nevi contain numerous senescent melanocytes without any immune clearance for unknown reasons.…”

Genotoxic stress modulates the release of exosomes from multiple myeloma cells capable of activating NK cell cytokine production: Role of HSP70/TLR2/NF-kB axis

“…17,18 More recently, low doses of chemotherapeutic drugs have been shown to induce immunogenic senescence and stimulate NK cell-mediated recognition and clearance of drugtreated tumor cells via the upregulation of NKG2D and DNAM-1 activating ligands on the surface of cancer cells. [19][20][21][22] An outstanding question concerns the role of tumor-derived exosomes (Tex) on the modulation of NK cell-mediated functions. The available evidence points to the molecular composition of the exosome cargo as a major determinant of the immunoregulatory activity of Tex on NK cells pointing to a prevailing, although not exclusive, inhibitory role.…”