expression analysis in melanomas and melanocytes from the same patient

DNA methylation is considered the primary epigenetic mechanism underlying the development of malignant melanoma. Since DNA methylation can be influenced by environmental factors, it is preferable to compare cancer and normal cells from the same patient. Here, we employed a novel epidermal sheet cultivation technique to isolate normal melanocytes from unaffected sites of melanoma patients and compared the methylation status with melanoma tissues from the same individuals. We also analyzed primary and metastatic melanoma samples, three commercially available melanocytes, and four melanoma cell lines. Cluster analysis of DNA methylation data classified freshly isolated melanomas and melanocytes into the same group, whereas the four melanoma cell lines were clustered together in a distant clade. Moreover, our analysis discovered methylation at several novel loci (KRTCAP3, AGAP2, ZNF490), in addition to those identified in previous studies (COL1A2, GPX3); however, the latter two were not observed in fresh melanoma samples. Subsequent studies revealed that NPM2 was hypermethylated and downregulated in melanomas, which was consistent with previous reports and indicated that NPM2 immunoreactivity could be used to differentiate melanomas from normal melanocytes or benign disease. Our results highlight the importance of using matched fresh melanoma and melanocyte samples in epigenetic studies. illumina HumanHT-12_v4 BeadChip total 10 samples, 5 melanocytes and 5 melanomas. Freshly isolated 2 pair of melanoma and melanocyte from the same patient, 3 commercial melanoma cell lines and 3 commercial melanocyte cell lines.