Interaction between tumor cell TNFR2 and monocyte membrane-bound TNF-alpha triggers tumorigenic inflammation in neuroblastoma

BackgroundTumor progression and resistance to therapy in children with neuroblastoma (NB), a common childhood cancer, are often associated with infiltration of monocytes and macrophages that produce inflammatory cytokines. However, the mechanism by which tumor-supportive inflammation is initiated and propagated remains unknown. Here, we describe a novel protumorigenic circuit between NB cells and monocytes that is triggered and sustained by tumor necrosis factor alpha (TNF-alpha).MethodsWe used NB knockouts (KOs) of TNF-alpha and TNFRSF1A mRNA (TNFR1)/TNFRSF1B mRNA (TNFR2) and TNF-alpha protease inbitor (TAPI), a drug that modulates TNF-alpha isoform expression, to assess the role of each component in monocyte-associated protumorigenic inflammation. Additionally, we employed NB-monocyte cocultures and treated these with clinical-grade etanercept, an Fc-TNFR2 fusion protein, to neutralize signaling by both membrane-bound (m) and soluble (s)TNF-alpha isoforms. Further, we treated NOD/SCID/IL2R gamma(null) mice carrying subcutaneous NB/human monocyte xenografts with etanercept and evaluated the impact on tumor growth and angiogenesis. Gene set enrichment analysis (GSEA) was used to determine whether TNF-alpha signaling correlates with clinical outcomes in patients with NB.ResultsWe found that NB expression of TNFR2 and monocyte membrane-bound tumor necrosis factor alpha is required for monocyte activation and interleukin (IL)-6 production, while NB TNFR1 and monocyte soluble TNF-alpha are required for NB nuclear factor kappa B subunit 1 (NF-kappa B) activation. Treatment of NB-monocyte cocultures with clinical-grade etanercept completely abrogated release of IL-6, granulocyte colony-stimulating factor (G-CSF), IL-1 alpha, and IL-1 beta and eliminated monocyte-induced enhancement of NB cell proliferation in vitro. Furthermore, etanercept treatment inhibited tumor growth, ablated tumor angiogenesis, and suppressed oncogenic signaling in mice with subcutaneous NB/human monocyte xenografts. Finally, GSEA revealed significant enrichment for TNF-alpha signaling in patients with NB that relapsed.ConclusionsWe have described a novel mechanism of tumor-promoting inflammation in NB that is strongly associated with patient outcome and could be targeted with therapy.