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DNA methylation analysis by DREAM of UV irradiated melanocytes

ABSTRACT: Ultraviolet radiation (UVR) is the greatest risk factor for melanoma development. While the role of UVR in DNA mutagenesis is generally accepted, the role of UVR-induced mutations in melanomagenesis remains controversial. To understand better how UVR is contributing to melanoma development, we investigated the non-mutational effect of UVR on the epigenome, specifically DNA methylation. Aberrant DNA methylation changes are a hallmark in melanoma and there are few reports on the effects of UVR on DNA methylation. We exposed melanocytes to UVR and cultured them for one-month to detect heritable and stable changes in DNA methylation. We found both hyper and hypo methylated sites after UVR exposure. While many of these changes occurred outside of promoters and areas of active gene expression, there were changes in promoter DNA methylation changes that correlated with changes in gene expression. These changes also correlated with those found in melanoma and UVR sensitive sites were prognostic of patient overall survival. Our work shows UVR-induced DNA methylation changes in melanocytes and may be a novel non-mutational mechanism in which UVR contributes to melanoma development.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE169695 | GEO | 2024/03/25

REPOSITORIES: GEO

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Project description:Melanoma genomes are often characterized by large numbers of sunlight-induced mutations. However, epigenetic alterations, in the form of aberrant DNA methylation patterns, are also abundant. Using MIRA-seq, we have carried out a comprehensive characterization of the DNA methylome in a series of metastatic melanoma samples and catalogued the methylation changes relative to normal melanocytes, the presumed cells of origin for these tumors. Individual melanoma tumors contained up to several thousand hypermethylated regions. We discovered 179 tumor-specific methylation peaks that were present in all (27/27) melanomas and may lend themselves as effective disease biomarkers, and 3124 methylation peaks were present in >40% of the tumors. We specifically examined the relationship between presence of the Polycomb mark, H3K27me3 in melanocytes and tumor-specific DNA methylation in melanoma. We found that 150 of the approximately 1,200 tumor-associated methylation peaks near transcription start sites (TSS) were H3K27me3-marked in melanocytes. Notably, DNA methylation in melanoma was specific for distinct H3K27me3 peaks rather than for H3K27me3-enriched regions with broad genomic coverage. Yet, there were also numerous H3K27me3 peak-associated TSS regions that were completely resistant to DNA methylation in tumors. Furthermore, a rather large group of genes became methylated in melanoma but lacked H3K27me3 in melanocytes. There was no relationship between presence of BRAF V600 mutations and the number of methylation peaks in individual tumors. Gene expression analysis showed a strong signature of upregulated immune response genes in melanomas presumably as a result of lymphocyte infiltration. Genes down-regulated in tumors were enriched for melanocyte differentiation and pigmentation factors. Overall, there was limited correlation between tumor-associated DNA methylation changes and changes in gene expression although distinct melanocyte differentiation genes including KIT, PAX3 and SOX10 became methylated and downregulated in melanoma. Examination of H3K27me3 histone modification in human normal melanocytes.

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DNA methylation analysis by DREAM of UV irradiated melanocytes

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