Loss of neurofibromin accelerates uveal and dermal melanoma formation driven by GNAQ

Neurofibromin is a very large and complex tumor suppressor, whose loss can synergize with other MAPK pathway mutations to promote melanoma in the skin. In this paper, we investigated whether NF1 loss has a role in other melanomas, such as those that form in the dermis or eye (uveal tract). We found that heterozygous 17q11.2 loss that includes the NF1 locus is an uncommon, but recurrent phenomenon in human dermal and uveal melanomas described previously. We studied the effects of Nf1 haploinsufficiency in mice expressing oncogenic GNAQ ^Q209L in melanocytes and Schwann cells of peripheral nerves using the Plp1-creERT transgene, with tamoxifen given at 5 weeks of age. Nf1 haploinsufficiency accelerated dermal and uveal melanoma formation. We studied the effects of Nf1 loss in these melanomas using RNAseq. Many of the differentially expressed genes were homologous to genes whose expression correlates with prognosis in human uveal melanoma. Of particular interest was the up-regulation of cAMP signaling and its connection to protein kinase A, which is mutant in malignant melanotic nerve sheath tumors (MMNSTs). An unexpected finding was that oncogenic GNAQ was sufficient by itself to drive peripheral nerve sheath-like neoplasms in the mice. Hence, these studies reveal new insight into both melanocyte and Schwann cell transformation.