Abstract
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 (MPNST) that are resistant to therapies. The aim of this study was to identify an additional pathway in the NF1 tumorigenesis. We focused our work on Wnt signaling 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. 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 knockdown 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 β-catenin was increased in NF1-silenced cell lines. Wnt pathway activation was strongly associated to both cancer stem cell reservoir and Schwann-mesenchymal transition. We highlighted the implication of Wnt pathway in NF1-associated tumorigenesis.
Highlights
Neurofibromatosis type 1 (NF1) is an autosomal dominant neurocutaneous disorder affecting 1 in 3,000 individuals worldwide [1]
We confirmed that the knockdown of neurofibromatosis type 1 (NF1) in Schwann cells but not in epithelial cells provoked the activation of Wnt pathway by functional transfection assays
We showed that the protein expression of active b-catenin was increased in NF1-silenced cell lines
Summary
Neurofibromatosis type 1 (NF1) is an autosomal dominant neurocutaneous disorder affecting 1 in 3,000 individuals worldwide [1]. NF1 patients have an increased risk of both benign and malignant tumors, NF1 is classified as a tumor predisposition syndrome. The most common tumors are benign peripheral nerve (UPEC), Ho^pital Henri-Mondor; 13Department of Dermatology, Ho^pital Henri-Mondor, Assistance Publique-Ho^pitaux de Paris (AP-HP) and EA 4393 LIC, UPEC, Creteil, France; 14Laboratoire d'Oncogenetique, Institut Curie, Ho^pital Rene Huguenin; FNCLCC, Saint-Cloud; and 15Genetics Division, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts
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