title: Profiling epigenetic inactivation of tumor suppressor genes in tumors and plasma from cutaneous melanoma patients.
abstract: Aberrant methylation of CpG islands in promoter regions of tumor suppressor genes (TSG) has been demonstrated in epithelial origin tumors. However, the methylation profiling of tumor-related gene promoter regions in cutaneous melanoma tumors has not been reported. Seven known or candidate TSGs that are frequently hypermethylated in carcinomas were assessed by methylation-specific polymerase chain reaction (MSP) in 15 melanoma cell lines and 130 cutaneous melanoma tumors. Four TSGs were frequently hypermethylated in 86 metastatic tumor specimens: retinoic acid receptor-beta2 (RAR-beta2) (70%), RAS association domain family protein 1A (RASSF1A) (57%), and O6-methylguanine DNA methylatransferase (MGMT) (34%), and death-associated protein kinase (DAPK) (19%). Hypermethylation of MGMT, RASSF1A, and DAPK was significantly lower in primary melanomas (n=20) compared to metastatic melanomas. However, hypermethylation of RAR-beta2 was 70% in both primary and metastatic melanomas. Cell lines had hypermethylation profiles similar to those of metastatic melanomas. The analysis of these four markers of metastatic tumors demonstrated that 97% had > or =1 gene(s) and 59% had > or =2 genes hypermethylated. The methylation of genes was verified by bisulfite sequencing. The mRNA transcripts could be re-expressed in melanoma cell lines having hypermethylated genes following treatment with 5'-aza 2'-deoxycytidine (5Aza-dC). Analysis of melanoma patients' plasma (preoperative blood; n=31) demonstrated circulating hypermethylated MGMT, RAR-beta2, and RASSF1A DNA for at least one of the markers in 29% of the patients. Our findings indicate that the incidence of TSG hypermethylation increases during tumor progression. Methylation of TSG may play a significant role in cutaneous melanoma progression.
authors.affiliation: Department Molecular Oncology, John Wayne Cancer Institute at Saint John's Health Center, 2200 Santa Monica Blvd, Santa Monica, CA 90404, USA. hoon@jwci.org
authors.forename: Dave S B
authors.initials: DS
authors.lastname: Hoon
authors.forename: Mia
authors.initials: M
authors.lastname: Spugnardi
authors.forename: Christine
authors.initials: C
authors.lastname: Kuo
authors.forename: Sharon K
authors.initials: SK
authors.lastname: Huang
authors.forename: Donald L
authors.initials: DL
authors.lastname: Morton
authors.forename: Bret
authors.initials: B
authors.lastname: Taback
mesh_terms: D004247:DNA / Q000097:blood; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D020868:Gene Silencing; D016147:Genes, Tumor Suppressor; D006801:Humans; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism; D012878:Skin Neoplasms / Q000235:genetics* / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D004247:DNA