The activation of the WNT signaling pathway is a Hallmark in neurofibromatosis type 1 tumorigenesis.
OBJECTIVE
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.


METHODS
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.


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 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.


CONCLUSIONS
We highlighted the implication of Wnt pathway in NF1-associated tumorigenesis.
Authors' Affiliations: UMR_S745 INSERM, Université Paris Descartes Sorbonne Paris Cité, Faculté des Sciences Pharmaceutiques et Biologiques; Department of Plastic and Reconstructive Surgery, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris (AP-HP), PRES Sorbonne Paris Cité; Service d'Anatomie et Cytologie Pathologiques, Assistance Publique-Hôpitaux de Paris (AP-HP), Hôpital Cochin, Université Paris Descartes; Service de Biochimie et de Génétique Moléculaire, Hôpital Cochin, Assistance Publique-Hôpitaux de Paris (AP-HP); UMR8194 CNRS, PRES Sorbonne Paris Cité, Paris Descartes; Department of Orthopedic Surgery, Cochin Hospital; Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, Assistance Publique-Hôpitaux de Paris (AP-HP), Hôpital Cochin, Laboratory of Biochemistry; Tumour bank, Cochin Hospital, Assistance Publique Hôpitaux de Paris, Paris Descartes University; INSERM, U1016, Institut Cochin, and CNRS, UMR8104, Paris; Département de pathologie Assistance Publique-Hôpitaux de Paris (AP-HP) and Université Paris Est Créteil (UPEC); Platform of Biological Ressources; Department of Plastic and Reconstructive Surgery, Assistance Publique-Hôpitaux de Paris (AP-HP) and Université Paris Est Créteil (UPEC), Hôpital Henri-Mondor; Department of Dermatology, Hôpital Henri-Mondor, Assistance Publique-Hôpitaux de Paris (AP-HP) and EA 4393 LIC, UPEC, Créteil, France; Laboratoire d'Oncogénétique, Institut Curie, Hôpital René Huguenin; FNCLCC, Saint-Cloud; and Genetics Division, Department of Medicine, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts.
Armelle
A
Luscan
Ghjuvan'ghjacumu
G
Shackleford
Julien
J
Masliah-Planchon
Ingrid
I
Laurendeau
Nicolas
N
Ortonne
Jennifer
J
Varin
François
F
Lallemand
Karen
K
Leroy
Valérie
V
Dumaine
Mikael
M
Hivelin
Didier
D
Borderie
Thomas
T
De Raedt
Laurence
L
Valeyrie-Allanore
Frédérique
F
Larousserie
Benoît
B
Terris
Laurent
L
Lantieri
Michel
M
Vidaud
Dominique
D
Vidaud
Pierre
P
Wolkenstein
Béatrice
B
Parfait
Ivan
I
Bièche
Charbel
C
Massaad
Eric
E
Pasmant
D015415:Biomarkers / Q000378:metabolism; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition; D005347:Fibroblasts / Q000378:metabolism; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D016130:Immunophenotyping; D008407:Mast Cells / Q000378:metabolism; D009455:Neurofibroma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009456:Neurofibromatosis 1 / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D025542:Neurofibromin 1 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D015203:Reproducibility of Results; D012583:Schwann Cells / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism; D060449:Wnt Signaling Pathway
D015415:Biomarkers; D025542:Neurofibromin 1; D012333:RNA, Messenger