LAUSR

Abstract Purpose: Acral melanoma is the major subtype of melanoma seen in Asian patients with melanoma and is featured by its insidious onset and poor prognosis. The genomic study that elucidates driving mutational events is fundamental to the development of gene-targeted therapy. However, research on genomic profiles of acral melanoma in Asian patients is still sparse. Experimental Design: We carried out whole-exome sequencing (WES) on 60 acral melanoma lesions (with 55 primary samples involved), targeted deep sequencing in a validation cohort of 48 cases, RNA sequencing in 37 acral melanoma samples (all from the 60 undergoing WES), and FISH in 233 acral melanoma specimens (54 of the 60 undergoing WES included). All the specimens were derived from Asian populations. Results: BRAF, NRAS, and KIT were discerned as significantly mutated genes (SMG) in acral melanoma. The detected COSMIC signature 3 related to DNA damage repair, along with the high genomic instability score, implied corresponding pathogenesis of acral melanoma. Moreover, the copy number gains of EP300 were associated with the response of acral melanoma to targeted therapy of A485 (a p300 inhibitor) and immune checkpoint blockade treatment. In addition, the temporal order in mutational processes of the samples was reconstructed, and copy-number alterations were identified as early mutational events. Conclusions: Our study provided a detailed view of genomic instability, potential therapeutic targets, and intratumoral heterogeneity of acral melanoma, which might fuel the development of personalized strategies for treating acral melanoma in Asian populations.