Mutually exclusive recurrent somatic mutations in MAP2K1 and BRAF support a central role for ERK activation in LCH pathogenesis

Blood. 2014 Nov 6;124(19):3007-15. doi: 10.1182/blood-2014-05-577825. Epub 2014 Sep 8.


Langerhans cell histiocytosis (LCH) is a myeloproliferative disorder characterized by lesions composed of pathological CD207(+) dendritic cells with an inflammatory infiltrate. BRAFV600E remains the only recurrent mutation reported in LCH. In order to evaluate the spectrum of somatic mutations in LCH, whole exome sequencing was performed on matched LCH and normal tissue samples obtained from 41 patients. Lesions from other histiocytic disorders, juvenile xanthogranuloma, Erdheim-Chester disease, and Rosai-Dorfman disease were also evaluated. All of the lesions from histiocytic disorders were characterized by an extremely low overall rate of somatic mutations. Notably, 33% (7/21) of LCH cases with wild-type BRAF and none (0/20) with BRAFV600E harbored somatic mutations in MAP2K1 (6 in-frame deletions and 1 missense mutation) that induced extracellular signal-regulated kinase (ERK) phosphorylation in vitro. Single cases of somatic mutations of the mitogen-activated protein kinase (MAPK) pathway genes ARAF and ERBB3 were also detected. The ability of MAPK pathway inhibitors to suppress MAPK kinase and ERK phosphorylation in cell culture and primary tumor models was dependent on the specific LCH mutation. The findings of this study support a model in which ERK activation is a universal end point in LCH arising from pathological activation of upstream signaling proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Dendritic Cells / metabolism
  • Disease Progression
  • Erdheim-Chester Disease / genetics
  • Erdheim-Chester Disease / metabolism
  • HEK293 Cells
  • Histiocytosis, Langerhans-Cell / genetics*
  • Histiocytosis, Langerhans-Cell / metabolism*
  • Histiocytosis, Sinus / genetics
  • Histiocytosis, Sinus / metabolism
  • Humans
  • MAP Kinase Kinase 1 / genetics*
  • MAP Kinase Kinase 1 / metabolism*
  • MAP Kinase Signaling System / genetics
  • Mutation, Missense
  • Proto-Oncogene Proteins B-raf / genetics*
  • Proto-Oncogene Proteins B-raf / metabolism*
  • Xanthogranuloma, Juvenile / genetics
  • Xanthogranuloma, Juvenile / metabolism


  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • MAP Kinase Kinase 1
  • MAP2K1 protein, human