Acute Inhibition of MEK Suppresses Congenital Melanocytic Nevus Syndrome in a Murine Model Driven by Activated NRAS and Wnt Signaling.

Pawlikowski JS, Brock C, Chen SC, Al-Olabi L, Nixon C, McGregor F, Paine S, Chanudet E, Lambie W, Holmes WM, Mullin JM, Richmond A, Wu H, Blyth K, King A, Kinsler VA, Adams PD
J Invest Dermatol. 2015 135 (8): 2093-2101

PMID: 25815427 · PMCID: PMC4539947 · DOI:10.1038/jid.2015.114

Congenital melanocytic nevus (CMN) syndrome is the association of pigmented melanocytic nevi with extra-cutaneous features, classically melanotic cells within the central nervous system, most frequently caused by a mutation of NRAS codon 61. This condition is currently untreatable and carries a significant risk of melanoma within the skin, brain, or leptomeninges. We have previously proposed a key role for Wnt signaling in the formation of melanocytic nevi, suggesting that activated Wnt signaling may be synergistic with activated NRAS in the pathogenesis of CMN syndrome. Some familial pre-disposition suggests a germ-line contribution to CMN syndrome, as does variability of neurological phenotypes in individuals with similar cutaneous phenotypes. Accordingly, we performed exome sequencing of germ-line DNA from patients with CMN to reveal rare or undescribed Wnt-signaling alterations. A murine model harboring activated NRAS(Q61K) and Wnt signaling in melanocytes exhibited striking features of CMN syndrome, in particular neurological involvement. In the first model of treatment for this condition, these congenital, and previously assumed permanent, features were profoundly suppressed by acute post-natal treatment with a MEK inhibitor. These data suggest that activated NRAS and aberrant Wnt signaling conspire to drive CMN syndrome. Post-natal MEK inhibition is a potential candidate therapy for patients with this debilitating condition.

MeSH Terms (18)

Animals Child Disease Models, Animal DNA Female Humans Male MAP Kinase Kinase Kinases Membrane Proteins Mice Mice, Inbred C57BL Monomeric GTP-Binding Proteins Mutation Nevus, Pigmented Sequence Analysis, DNA Signal Transduction Skin Neoplasms Wnt Proteins

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