The activation of the WNT signalling pathway is a hallmark in Neurofibromatosis type 1 tumorigenesis
Menée sur 57 échantillons tumoraux et in vitro, cette étude française met en évidence le rôle joué par la signalisation Wnt dans la tumorigenèse d'une neurofibromatose de type 1
Purpose: The hallmark of neurofibromatosis type 1 (NF1) is the onset of dermal or plexiform neurofibromas, mainly composed of Schwann cells. Plexiform neurofibromas can transform into malignant peripheral nerve sheath tumors (MPNSTs) that are resistant to therapies. Experimental design: The aim of this study was to identify an additional pathway in the NF1-tumorigenesis. We focused our work on Wnt signalling that is highly implicated in cancer, mainly in regulating the proliferation of cancer stem cells. We quantified mRNAs of 89 Wnt pathway genes in 57 NF1-associated tumors including dermal and plexiform neurofibromas and MPNSTs. Expression of two major stem cell marker genes and five major epithelial-mesenchymal transition marker genes was also assessed. The expression of significantly deregulated Wnt genes was then studied in normal human Schwann cells, fibroblasts, endothelial cells, and mast cells and in seven MPNST cell lines. Results: The expression of nine Wnt genes was significantly deregulated in plexiform neurofibromas in comparison with dermal neurofibromas. Twenty Wnt genes showed altered expression in MPNST biopsies and cell lines. Immunohistochemical studies confirmed the Wnt pathway activation in NF1-associated MPNSTs. We then confirmed that the knock-down of NF1 in Schwann cells but not in epithelial cells provoked the activation of Wnt pathway by functional transfection assays. Furthermore, we showed that the protein expression of active beta-catenin was increased in NF1-silenced cell lines. Wnt pathway activation was strongly associated to both cancer stem cell reservoir and Schwann-mesenchymal transition. Conclusion: We highlighted the implication of Wnt pathway in NF1-associated tumorigenesis.