Article

Distinct sets of genetic alterations in melanoma.

Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143-0808, USA.
New England Journal of Medicine (Impact Factor: 54.42). 12/2005; 353(20):2135-47. DOI: 10.1056/NEJMoa050092
Source: PubMed

ABSTRACT Exposure to ultraviolet light is a major causative factor in melanoma, although the relationship between risk and exposure is complex. We hypothesized that the clinical heterogeneity is explained by genetically distinct types of melanoma with different susceptibility to ultraviolet light.
We compared genome-wide alterations in the number of copies of DNA and mutational status of BRAF and N-RAS in 126 melanomas from four groups in which the degree of exposure to ultraviolet light differs: 30 melanomas from skin with chronic sun-induced damage and 40 melanomas from skin without such damage; 36 melanomas from palms, soles, and subungual (acral) sites; and 20 mucosal melanomas.
We found significant differences in the frequencies of regional changes in the number of copies of DNA and mutation frequencies in BRAF among the four groups of melanomas. Samples could be correctly classified into the four groups with 70 percent accuracy on the basis of the changes in the number of copies of genomic DNA. In two-way comparisons, melanomas arising on skin with signs of chronic sun-induced damage and skin without such signs could be correctly classified with 84 percent accuracy. Acral melanoma could be distinguished from mucosal melanoma with 89 percent accuracy. Eighty-one percent of melanomas on skin without chronic sun-induced damage had mutations in BRAF or N-RAS; the majority of melanomas in the other groups had mutations in neither gene. Melanomas with wild-type BRAF or N-RAS frequently had increases in the number of copies of the genes for cyclin-dependent kinase 4 (CDK4) and cyclin D1 (CCND1), downstream components of the RAS-BRAF pathway.
The genetic alterations identified in melanomas at different sites and with different levels of sun exposure indicate that there are distinct genetic pathways in the development of melanoma and implicate CDK4 and CCND1 as independent oncogenes in melanomas without mutations in BRAF or N-RAS.

1 Bookmark
 · 
86 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: BACKROUND In patients with metastatic melanoma and KIT amplifications and/or mutations, therapy with imatinib mesylate may prolong survival. 18F-labeled 2-fluoro-2-deoxy-D-glucose (18F-FDG) PET/CT may be used to assess metabolic response. We investigated associations of metabolic response, mutational status, progression-free survival and overall survival in this population. METHODS: Baseline and 4-week follow-up 18F-FDG-PET/CT were evaluated in 17 patients with metastatic melanoma and KIT amplifications and/or mutations treated with imatinib in a multicenter phase II clinical trial. The maximum standardized uptake values (SUVmax) were measured in up to 10 lesions on each scan. Metabolic response was classified using modified EORTC criteria. Each patient had a diagnostic CT or MR at baseline, after 6 weeks of therapy and then at intervals of 2 months and anatomic response was classified using RECIST 1.0. Median follow-up was 9.8 months. RESULTS: Partial metabolic response (PMR), stable metabolic disease (SMD) and progressive metabolic disease (PMD) was seen in 5 (29%), 5 (29%), and 7 (41%) patients respectively. Five patients (29%) had a KIT mutation in exon 11, four of whom (80%) had PMR while 1 (20%) had SMD. Twelve patients (71%) did not have a KIT mutation in exon 11, and only 1 (8%) had PMR, 4 (33%) had SMD and 7 (58%) had PMD. There was agreement of metabolic and anatomic classification in 12 of 17 patients (71%). Four of 17 patients (24%) had PR on both metabolic and anatomic imaging and all had a KIT mutation in exon 11. Survival of patients with PMD was lower than with SMD or PMR. CONCLUSIONS: Metabolic response by 18F-FDG-PET/CT is associated with mutational status in metastatic melanoma patients treated with imatinib. 18F-FDG-PET/CT may be a predictor of outcome, although a larger study is needed to verify this.
    Cancer Imaging 11/2014; 14(1):30. · 1.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Malignant melanoma is an aggressive cutaneous neoplasm whose incidence has continued to increase worldwide. Currently, histopathologic examination of specimens is the gold standard for the diagnosis and categorization of melanoma. Cytogenetic analysis represents a powerful, and currently underused, adjunct to traditional histologic examination in distinguishing nevi and melanomas. Chromosomal studies have shown that malignant melanomas often contain multiple chromosomal alterations, most commonly of chromosomes 1, 6, 7, 9, 10 and 11. These chromosomes often include genes within the MAPK molecular pathway, which is involved in the development and progression of melanoma. Fluorescence in situ hybridization (FISH) can detect a number of recurrent anomalies, and commercially available kits for melanoma detection have been devised. The utility of cytogenetics in melanocytic lesions at certain anatomic sites has been evaluated, including acral lesions, uveal lesions, and lymph node metastases. Recurring cytogenetic anomalies have been defined in various challenging histologic subtypes, such as desmoplastic melanomas and Spitzoid lesions. Cytogenetic analysis may also be used to provide supplementary information in prognostication, particularly in uveal melanomas. We provide a brief review of the molecular pathways found in melanoma and a summary of what is known and remains unknown regarding cytogenetic aberrations associated with malignant melanoma. Keywords: nevus, nodal nevus, blue nevus, cutaneous melanoma, desmoplastic melanoma, uveal melanoma, blue nevus-like melanoma, cytogenetics, FISH, fluorescence in situ hybridization
    Journal of the Association of Genetic Technologists 10/2014; 40(4):209-218.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The present study identified miR-638 as one of the most significantly overexpressed miRNAs in metastatic lesions of melanomas compared with primary melanomas. miR-638 enhanced the tumorigenic properties of melanoma cells in vitro and lung colonization in vivo. mRNA expression profiling identified new candidate genes including TP53INP2 as miR-638 targets, the majority of which are involved in p53 signalling. Overexpression of TP53INP2 severely attenuated proliferative and invasive capacity of melanoma cells which was reversed by miR-638. Depletion of miR-638 stimulated expression of p53 and p53 downstream target genes and induced apoptosis and autophagy. miR-638 promoter analysis identified the miR-638 target transcription factor associated protein 2α (TFAP2A/AP-2α) as a direct negative regulator of miR-638, suggestive for a double-negative regulatory feedback loop. Taken together, miR-638 supports melanoma progression and suppresses p53-mediated apoptosis pathways, autophagy and expression of the transcriptional repressor TFAP2A/AP-2α.
    Oncotarget 12/2014; · 6.63 Impact Factor

Full-text

Download
7 Downloads
Available from
Sep 24, 2014

John A. Curtin