Analysis of Variants Induced by Combined Ex Vivo Irradiation and In Vivo Tumorigenesis Suggests a Role for the ZNF831 p.R1393Q Variant in Cutaneous Melanoma Development.

UVR is known to be the most important environmental carcinogen for cutaneous melanoma. Whereas genomic analyses of melanoma tumors implicate a high rate of UV damage, the experimental induction and recovery of bona fide UV-signature changes have not been directly observed. To replicate recurrent UV variants from The Cancer Genome Atlas_SKCM specimens, we UV irradiated cultured immortalized human melanocytes and subjected them to in vivo tumorigenesis assays. Exome sequencing of the xenografted tumors revealed an increase in UV-signature mutations within the tumors and identified 48 induced variants that overlap with The Cancer Genome Atlas skin cutaneous melanoma UV-hotspot mutations. A UV-induced mutation, ZNF831 p.R1393Q, was correlated with a decreased survival (hazard ratio = 5.44, 95% confidence interval = 1.92-15.47, P = .0015) and was preferentially observed in melanomas compared with that in all The Cancer Genome Atlas tumors (P = 4.42 × 10-7). In addition, ZNF831 mRNA expression loss was strongly associated with decreased patient survival (hazard ratio = 2.14, 95% confidence interval = 1.62-2.83, P = 7.91 × 10-8), although the transcripts may arise from multiple cell types, including T cells. In multiple melanoma lines, overexpression of wild-type ZNF831 reduced spheroid growth, heightened apoptosis, and increased cell motility, with the ZNF831 p.R1393Q variant partially or wholly abolishing these functional phenotypes. We thus experimentally recovered a "functional UV-hotspot mutation" in ZNF831 that is altered in human melanoma specimens.