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

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 H2O2 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.

Gain-of-function FHF1 mutation causes early-onset epileptic encephalopathy with cerebellar atrophy.

OBJECTIVE: Voltage-gated sodium channel (Nav)-encoding genes are among early-onset epileptic encephalopathies (EOEE) targets, suggesting that other genes encoding Nav-binding proteins, such as fibroblast growth factor homologous factors (FHFs), may also play roles in these disorders. METHODS: To identify additional genes for EOEE, we performed whole-exome sequencing in a family quintet with 2 siblings with a lethal disease characterized by EOEE and cerebellar atrophy. The pathogenic nature and functional consequences of the identified sequence alteration were determined by electrophysiologic studies in vitro and in vivo. RESULTS: A de novo heterozygous missense mutation was identified in the FHF1 gene (FHF1AR114H, FHF1BR52H) in the 2 affected siblings. The mutant FHF1 proteins had a strong gain-of-function phenotype in transfected Neuro2A cells, enhancing the depolarizing shifts in Nav1.6 voltage-dependent fast inactivation, predicting increased neuronal excitability. Surprisingly, the gain-of-function effect is predicted to result from weaker interaction of mutant FHF1 with the Nav cytoplasmic tail. Transgenic overexpression of mutant FHF1B in zebrafish larvae enhanced epileptiform discharges, demonstrating the epileptic potential of this FHF1 mutation in the affected children. CONCLUSIONS: Our data demonstrate that gain-of-function FHF mutations can cause neurologic disorder, and expand the repertoire of genetic causes (FHF1) and mechanisms (altered Nav gating) underlying EOEE and cerebellar atrophy.