Abstract 2045: Identifying key molecular events at the onset of melanoma using a neural crest stem cell marker

Abstract

Abstract An ongoing challenge in cancer biology is understanding the earliest, initiating events that switch a premalignant cell into a fully competent cancer cell. Driven by this challenge, we focused on the zebrafish gene crestin that marks the embryonic neural crest from the onset of somitogenesis through 72 hours post fertilization when it normally turns off. Surprisingly, our lab previously showed that crestin mRNA is reexpressed in melanoma tumors in adult zebrafish, reading out a neural crest progenitor state. We have developed a fluorescent reporter using the crestin promoter/enhancer that recapitulates the embryonic expression pattern of crestin, and when bred into our BRAFV600E/p53 mutant melanoma zebrafish model, marks grossly visible melanoma tumors. Remarkably, we found that crestin:EGFP becomes active when lesions are only a few cells in number, potentially in the first cell of the melanoma. Using a crestin:CreERt2 inducible recombinase together with a lox-dependent fluorescent lineage tracer line ubi:switch, multiple neural crest descendant lineages including melanocytes can be traced. Further by expressing the melanocyte lineage master transcription factor mitf under the control of the crestin promoter, we can rescue melanocyte formation in mitf null embryos, and in the Na/BRAFV600E/p53 melanoma-prone mutant background, some adult fish develop darkly pigmented patches and melanoma tumors. Finally, we isolated small patches of crestin:EGFP positive cells and show that these precursor lesions are enriched for expression of the neural crest progenitor transcription factor sox10. These data support a model in which BRAFV600E/p53 mutated melanocytes stochastically reactivate an early melanocyte or neural crest progenitor program as read out by crestin reactivation at the initiation of melanoma formation. Using our novel reporter, we are able to analyze in vivo the earliest steps of cancer formation as well as the neural crest lineage program. Citation Format: Charles K. Kaufman, Christian Mosimann, Richard M. White, Dominic Matos, Leonard I. Zon. Identifying key molecular events at the onset of melanoma using a neural crest stem cell marker. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2045. doi:10.1158/1538-7445.AM2014-2045