(American Association for the Advancement of Science (AAAS), 2018-11-01) Ablain, Julien; Xu, Mengshu; Rothschild, Harriet; Jordan, Richard C.; Mito, Jeffrey; Daniels, Brianne H.; Bell, Caitlin F.; Joseph, Nancy M.; Wu, Hong; Bastian, Boris C.; Zon, Leonard; Yeh, Iwei
Melanomas originating from mucosal surfaces have low mutation burden, genomic instability, and poor prognosis. To identify potential driver genes, we sequenced hundreds of cancer-related genes in 43 human mucosal melanomas, cataloguing point mutations, 5 amplifications and deletions. The SPRED1 gene, which encodes a negative regulator of MAPK signaling, was inactivated in 37% of the tumors. Four distinct genotypes were associated with SPRED1 loss. Using a rapid, tissue-specific CRISPR technique to model these genotypes in zebrafish, we found that SPRED1 functions as a tumor suppressor, particularly in the context of KIT mutations. SPRED1 knockdown caused MAPK 10 activation, increased cell proliferation and conferred resistance to drugs inhibiting KIT tyrosine kinase activity. These findings provide a rationale for MAPK inhibition in SPRED1-deficient melanomas and introduce a zebrafish modeling approach that can be used more generally to dissect genetic interactions in cancer.
