Elucidating the origins of melanoma

Grantee: A. Hunter Shain

Amount: DKK 2,500,000

The overarching goal of this grant is to better understand the origins of melanomas that appear suddenly, or de novo.

Approximately 70% of melanomas appear in this way, while the remainder grow out of preexisting nevi. Nevi can be monitored and prophylactically removed if they show signs of change, but melanomas that arise de novo are impossible to foresee. It is therefore of utmost importance to understand the origins of melanomas that appear de novo in order to develop biomarkers to predict their emergence.

We previously sequenced melanomas adjacent to nevi, revealing two classes of mutations – initiating mutations (emerging in nevi) and progression mutations (emerging in melanoma). Here, we hypothesize that progression mutations can precede initiating mutations. In this scenario, a melanocyte silently accumulates progression-associated mutations, followed by an initiating mutation so that the ensuing neoplasm ‘skips’ the precursor stages, manifesting directly as a melanoma.

If validated, this hypothesis would explain how de novo melanomas evolve. Here, we will genotype individual melanocytes from healthy human skin to test whether morphologically normal melanocytes can harbour progression mutations. Towards this goal, we have developed innovative solutions to establish high-quality genotyping calls from individual cells. In our preliminary data, we genotyped 17 melanocytes collected from healthy skin, and pathogenic mutations were surprisingly common, supporting our hypothesis. We will extend these studies to fully delineate the spectrum of cancer-associated mutations in melanocytes from healthy skin.

Overall, completion of these studies will reveal the origins of melanomas that do not pass through a precursor stage – a longstanding goal in the skin research community.