Genomic alterations of dermatofibrosarcoma protuberans revealed by whole-genome sequencing.

backgroundDermatofibrosarcoma protuberans (DFSP) is a rare and marginal cutaneous sarcoma of intermediate-grade malignancy, for which the genomic landscape remains unclear. Understanding the landscape of DFSP will help to further classify the genomic pathway of malignant development in soft tissue.

objectivesTo identify the comprehensive molecular pathogenesis of DFSP.

methodsIn this study, the comprehensive genomic features, with 53 tumour-normal pairs of DFSP, were revealed by whole-genome sequencing.

resultsThe mutational signature 1 (C > T mutation at CpG dinucleotides) is featured in DFSP, resulting in higher mutations in DNA replication. Interestingly, the recurrence of DFSP is correlated with low tumour mutation burden. Novel mutation genes in DFSP were identified, including MUC4/6, KMT2C and BRCA1, and subsequently, three molecular subtypes of DFSP were classified on the basis of MUC4 and MUC6 mutations. Various structural aberrations including genomic rearrangements were identified in DSFPs, particularly in 17q and 22q, which cause oncogene amplification (AKT1, SPHK1, COL1A1, PDGFβ) or tumour suppressor deletion (CDKN2A/B). In addition to gene fusion of COL1A1-PDGFβ [t(17;22)], we identified gene fusion of SLC2A5-BTBD7 [t(1;14)] in DFSP through whole-genome sequencing, and verified it experimentally. Enrichment analysis of altered molecules revealed that DNA repair, cell cycle, phosphoinositide 3-kinase and Janus kinase pathways were primarily involved in DFSP.

conclusionsThis is the first large-scale whole-genome sequencing for DFSP, and our findings describe the comprehensive genomic landscape, highlighting the molecular complexity and genomic aberrations of DFSP. Our findings also provide novel potential diagnostic and therapeutic targets for this disease. What is already known about this topic? Chromosomal translocation between chromosome 17 and chromosome 22 is the main feature in the pathogenesis of dermatofibrosarcoma protuberans (DFSP). What does this study add? We describe the comprehensive genomic landscape of DFSP, highlighting the molecular complexity and genomic aberrations. Our findings provide novel potential diagnostic and therapeutic targets for this disease. What is the translational message? Our study revealed novel molecular subtypes of DFSP based on genetic mutations, which benefits precision diagnosis. We also found oncogene amplification, including AKT1 and SPHK1, which provides novel potential target molecules for further DFSP treatment. In addition to gene fusion of COL1A1-PDGFβ, we identified a novel gene fusion of SLC2A5-BTBD7 in DFSP, which is a novel potential diagnostic and therapeutic target for this disease.