An inflammatory gene signature distinguishes neurofibroma Schwann cells and macrophages from cells in the normal peripheral nervous system

Abstract

Neurofibromas are benign peripheral nerve tumors driven by NF1 loss in Schwann cells (SCs). Macrophages are abundant in neurofibromas, and macrophage targeted interventions may have therapeutic potential in these tumors. We generated gene expression data from fluorescence-activated cell sorted (FACS) SCs and macrophages from wild-type and mutant nerve and neurofibroma to identify candidate pathways involved in SC-macrophage cross-talk. While in 1-month-old Nf1 mutant nerve neither SCs nor macrophages significantly differed from their normal counterparts, both macrophages and SCs showed significantly altered cytokine gene expression in neurofibromas. Computationally reconstructed SC-macrophage molecular networks were enriched for inflammation-associated pathways. We verified that neurofibroma SC conditioned medium contains macrophage chemo-attractants including colony stimulation factor 1 (CSF1). Network analysis confirmed previously implicated pathways and predict novel paracrine and autocrine loops involving cytokines, chemokines, and growth factors. Network analysis also predicted a central role for decreased type-I interferon signaling. We validated type-I interferon expression in neurofibroma by protein profiling, and show that treatment of neurofibroma-bearing mice with polyethylene glycolyated (PEGylated) type-I interferon-α2b reduces the expression of many cytokines overexpressed in neurofibroma. These studies reveal numerous potential targetable interactions between Nf1 mutant SCs and macrophages for further analyses.

Cxcr3-expressing leukocytes are necessary for neurofibroma formation in mice

“…CXCR3 ligand production is frequently associated with a myeloid cell response to IFN-γ signaling (46,47). IFN-γ is unlikely to drive Cxcl10 expression in neurofibroma; however, because Ifng expression is not detectable early in neurofibroma formation, in 2-month Dhh-Cre Nf1 fl/fl nerve/DRG, IFN-γ levels in neurofibroma are low relative to other relevant cytokines (17). Rather, it appears that SCs, like CNS glia, produce Cxcl10 in an IFN-γ-independent fashion (47), because we found that Cxcl10 expression in 2-month Dhh-Cre Nf1 fl/fl nerve/DRG localized to cell clusters expressing SC-associated genes.…”

“…In contrast, expression of Cxcl10 negatively correlated with expression of Ngfr and Gap43, markers that are associated with Remak SCs in vivo. In neurofibroma, when Ngfr-expressing SCs become axon dissociated, they secrete macrophage and mast cell chemokines (16,17,(50)(51)(52) but not Cxcl10. These data suggest that distinct SC subsets in neurofibromas produce different chemokines that contribute to tumor formation.…”

“…Plexiform neurofibromas and NF1-null Schwann cells demonstrate increased active Ras (Ras-GTP) (11,12) and the activation of Ras downstream pathways (13)(14)(15). Notably, NF1-null Schwann cells show increased expression of leukocyte chemoattractants, including CCL2, and stem cell factor (SCF) (16,17). Loss of NF1 also induces cellular senescence in a subset of neurofibroma cells, which may facilitate the production of additional inflammatory mediators (18).…”

Contributions of inflammation and tumor microenvironment to neurofibroma tumorigenesis

“…Therefore, we evaluated other inflammatory signatures in these neurofibroma tumors. Macrophage is another type of inflammatory cell found in neurofibroma (40,41). Similar to mast cells, removed from the tumor microenvironment suggested that mast cells are a modifier rather than a driver in neurofibroma development ( Figure 2C).…”

Integrative analysis identifies candidate tumor microenvironment and intracellular signaling pathways that define tumor heterogeneity in NF1

“…Others using genomic approaches to explore nerve sheath tumor biology identified MET and HGF amplification in MPNSTs; furthermore, models of MET amplified MPNSTs were subsequently sensitive to the MET inhibitor capmatinib [7] . Transcriptomics-focused approaches have also identified molecular features like MEK signaling, type 1 interferon signaling, and Aurora kinase A as putative therapeutic targets in NF1 tumors [12][13][14] . Taken together, these and other studies suggest that an integrative approach that combines multiple transcriptomic and genomic datasets might be well poised to identify new therapeutic avenues in MPNSTs and other NF1 related nerve sheath tumors.…”