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Increase in NRAS mutant allele percentage during metastatic melanoma progression
Author(s) -
FunckBrentano Elisa,
HéliasRodzewicz Zofia,
Longvert Christine,
Mokhtari Karima,
Saiag Philippe,
Emile JeanFrançois
Publication year - 2016
Publication title -
experimental dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.108
H-Index - 96
eISSN - 1600-0625
pISSN - 0906-6705
DOI - 10.1111/exd.13001
Subject(s) - neuroblastoma ras viral oncogene homolog , cancer research , polysomy , lymph node , allele , melanoma , medicine , cancer , mutation , biology , pathology , kras , chromosome , gene , genetics , fluorescence in situ hybridization
One‐fifth of cutaneous melanomas have dominant gain‐of‐function mutations of the NRAS oncogene. We report the first two cases of increasing NRAS mutant allele frequency in melanoma metastases and show that the chromosomal mechanism of this homozygosity is an increased polysomy of chromosome 1. We observed an increase in NRAS mutant allele percentage ( NRAS ‐ MA %) in the metastatic melanoma progression from 2 patients with melanomas harbouring a NRAS mutation (p.Q61K in case 1 and p.Q61R in case 2). In case 1, we observed a NRAS ‐ MA % increase from 18% within the first metastatic node to 81%, 92% and 85% respectively in the three subsequent metastases: lymph node, brain and subcutaneous metastases biopsied 1, 6 and 17 months, respectively, after the initial lymph node biopsy. In case 2, we observed an increase in NRAS ‐ MA % from 40% within the primary melanoma to 63% within the metastatic lymph node. FISH analysis showed the same results in both cases: a frequent polysomy of chromosome 1 in metastasis samples with NRAS mutant allele percentage >60%, while most cells were disomic in the samples with well‐balanced heterozygous mutations. The percentage of NRAS mutant allele may increase during metastatic progression and may be associated with chromosomal instability. Further studies are needed to evaluate the prognostic impact of the NRAS homozygous status and/or polyploidy in metastatic cutaneous melanomas.