Pathogen response-like recruitment and activation of neutrophils by sterile immunogenic dying cells drives neutrophil-mediated residual cell killing

Abstract

Innate immune sensing of dying cells is modulated by several signals. Inflammatory chemokines-guided early recruitment, and pathogen-associated molecular patterns-triggered activation, of major anti-pathogenic innate immune cells like neutrophils distinguishes pathogen-infected stressed/dying cells from sterile dying cells. However, whether certain sterile dying cells stimulate innate immunity by partially mimicking pathogen response-like recruitment/activation of neutrophils remains poorly understood. We reveal that sterile immunogenic dying cancer cells trigger (a cell autonomous) pathogen response-like chemokine (PARC) signature, hallmarked by co-release of CXCL1, CCL2 and CXCL10 (similar to cells infected with bacteria or viruses). This PARC signature recruits preferentially neutrophils as first innate immune responders in vivo (in a cross-species, evolutionarily conserved manner; in mice and zebrafish). Furthermore, key danger signals emanating from these dying cells, that is, surface calreticulin, ATP and nucleic acids stimulate phagocytosis, purinergic receptors and toll-like receptors (TLR) i.e. TLR7/8/9-MyD88 signaling on neutrophil level, respectively. Engagement of purinergic receptors and TLR7/8/9-MyD88 signaling evokes neutrophil activation, which culminates into H 2 O 2 and NO-driven respiratory burst-mediated killing of viable residual cancer cells. Thus sterile immunogenic dying cells perform 'altered-self mimicry' in certain contexts to exploit neutrophils for phagocytic targeting of dead/ dying cancer cells and cytotoxic targeting of residual cancer cells.

Priming anti-tumor immunity by radiotherapy: Dying tumor cell-derived DAMPs trigger endothelial cell activation and recruitment of myeloid cells

“…Neutrophil recruitment by dying tumor cells has been described recently in a mouse model where culture supernatants of tunicamycin- or mitoxanthrone-treated tumor cells were injected into the ear pinnae and in different mouse flank tumors irradiated with high single doses of 15 Gy, 48,49 thus confirming our air pouch findings. The authors of both studies also observed an essential contribution of CXCL1 together with CCL2, CXCL10, and G-CSF.…”

“…Yet, evidence is available that neutrophils can engulf dying tumor cells, exert cytotoxic activity against residual, therapy-surviving tumor cells, and thus can contribute to therapy-induced tumor control. 48,49 Additionally, neutrophils are able to create a favorable chemokine milieu for the invasion of monocytic cells and tumor-specific cytotoxic T cells. 45,49 …”

Trial watch: Immunogenic cell death induction by anticancer chemotherapeutics

“…210 We also discovered that cancer cells undergoing mitoxantrone-induced ICD trigger a pathogen response-like chemokine (PARC) signature characterized by the co-release of C-X-C motif chemokine ligand 1 (CXCL1), C-C motif chemokine ligand 2 (CCL2) and C-X-C motif chemokine ligand 10 (CXCL10) (or homologues thereof), in thus far mimicking bacteria or virus infected cells. 97 Such a chemokine mixture is particularly efficient at recruiting neutrophils towards the dying cells (a process that appears to be evolutionarily conserved), paving the way to the CALR-dependent phagocytosis of dying cancer cells or corpses thereof, and the cytotoxic targeting of residual malignant cells. 97 We characterized a naturally-occurring preclinical model of cancer that exhibits intrinsic resistance against mitoxantrone-induced ICD in vivo secondary to a defect in CALR exposure, 199 and we documented that anthracyclines and oxaliplatin can trigger a necroptotic variant of ICD [211][212][213][214][215] in cancer cells expressing receptor interacting serine/threonine kinase 3 (RIP3K) and the pseudokinase mixed lineage kinase domain-like (MLKL).…”

“…40,83 In the case of chemotherapy-induced ICD, these include (but may not be limited to): (1) surface-exposed endoplasmic reticulum (ER) chaperones including calreticulin (CALR) [84][85][86] ; (2) extracellular ATP; [87][88][89][90][91] (3) extracellular high mobility group box 1 (HMGB1) 13,92 ; (4) extracellular annexin A1 (ANXA1) 55 ; (5) secreted type I interferon; [93][94][95][96] and (6) extracellular nucleic acids. 97 That said, ICD triggered by stimuli other than chemotherapy (e.g., radiation therapy, photodynamic therapy) is not necessarily associated with the same DAMPs. 3,40,98,99 Moreover, new DAMPs underlying the immunogenicity of specific instances of RCD are continuously being uncovered (see below).…”

“…[105][106][107][108][109][110] Accordingly, RCD can no longer be perceived as immunogenic when: (1) the intracellular stress responses regulating the emission of ICD-associated DAMPs are pharmacologically or genetically ablated in cancer cells; or (2) when the molecular machinery dedicated to DAMP detection is inhibited or ablated. 13,44,84,91,93,97 Moreover, ICD-driven immunity can no longer operate in the presence of general immunological defects, 111 such as (1) an intrinsically low antigenicity of cancer cells, owing to low levels of TAAs or downregulation of MHC Class I molecules [112][113][114][115][116][117][118][119] ; (2) an increased immunological tolerance of the host, secondary to increased amounts of immunosuppressive cytokines, [120][121][122][123][124][125][126][127][128] or inhibitors of chemotaxis, [129][130][131][132][133][134] increased tumor infiltration by immunosuppressive cell populations, [135][136][137][138][139][140]…”