Genomic profiling with whole-exome sequencing revealed distinct mutations and novel pathways in Asian melanoma

The clinical characteristics of malignant melanoma are highly variable between patient populations of different ethnicities. To explore the underlining genetic variations, we reviewed the clinical data of 242 malignant melanoma cases from Taiwan and among them submitted formalin-fixed paraffin-embedded tissue samples from 37 patients for whole-exome sequencing to identify the mutational signatures, tumor mutation burden and specific gene mutations. The genomic profiles and clinical outcomes were compared with the information derived from the publicly available TCGA and TGEN databases. Mutation signature 12 was the dominant signature in Taiwanese patients and represented approximately 45% of the mutation signatures observed. In contrast, mutation signature 7 was the most prominent among cases available in the TCGA database. Common gene mutations found in the TCGA melanoma dataset were not frequently found in melanomas from Taiwanese patients. There were a significant number of specific gene mutations that exclusively occurred in acral subtype but not in non-acral subtype melanomas, and vice versa. While certain common mutations form a shared core of genetic features, there appear to be specific genetic pathways that are involved in the occurrence of melanomas that grow in non-UV-exposed areas. Our findings have shed light on the tumorigenesis pathways involved in malignant melanoma.