|Title||An ultraviolet-radiation-independent pathway to melanoma carcinogenesis in the red hair/fair skin background.|
|Publication Type||Journal Article|
|Year of Publication||2012|
|Authors||Mitra, D, Luo, X, Morgan, A, Wang, J, Hoang, MP, Lo, J, Guerrero, CR, Lennerz, JK, Mihm, MC, Wargo, JA, Robinson, KC, Devi, SP, Vanover, JC, D'Orazio, JA, McMahon, M, Bosenberg, MW, Haigis, KM, Haber, DA, Wang, Y, Fisher, DE|
|Date Published||2012 Oct 31|
|Keywords||cancer, health, melanin, pigmentation|
People with pale skin, red hair, freckles and an inability to tan-the 'red hair/fair skin' phenotype-are at highest risk of developing melanoma, compared to all other pigmentation types. Genetically, this phenotype is frequently the product of inactivating polymorphisms in the melanocortin 1 receptor (MC1R) gene. MC1R encodes a cyclic AMP-stimulating G-protein-coupled receptor that controls pigment production. Minimal receptor activity, as in red hair/fair skin polymorphisms, produces the red/yellow pheomelanin pigment, whereas increasing MC1R activity stimulates the production of black/brown eumelanin. Pheomelanin has weak shielding capacity against ultraviolet radiation relative to eumelanin, and has been shown to amplify ultraviolet-A-induced reactive oxygen species. Several observations, however, complicate the assumption that melanoma risk is completely ultraviolet-radiation-dependent. For example, unlike non-melanoma skin cancers, melanoma is not restricted to sun-exposed skin and ultraviolet radiation signature mutations are infrequently oncogenic drivers. Although linkage of melanoma risk to ultraviolet radiation exposure is beyond doubt, ultraviolet-radiation-independent events are likely to have a significant role. Here we introduce a conditional, melanocyte-targeted allele of the most common melanoma oncoprotein, BRAF(V600E), into mice carrying an inactivating mutation in the Mc1r gene (these mice have a phenotype analogous to red hair/fair skin humans). We observed a high incidence of invasive melanomas without providing additional gene aberrations or ultraviolet radiation exposure. To investigate the mechanism of ultraviolet-radiation-independent carcinogenesis, we introduced an albino allele, which ablates all pigment production on the Mc1r(e/e) background. Selective absence of pheomelanin synthesis was protective against melanoma development. In addition, normal Mc1r(e/e) mouse skin was found to have significantly greater oxidative DNA and lipid damage than albino-Mc1r(e/e) mouse skin. These data suggest that the pheomelanin pigment pathway produces ultraviolet-radiation-independent carcinogenic contributions to melanomagenesis by a mechanism of oxidative damage. Although protection from ultraviolet radiation remains important, additional strategies may be required for optimal melanoma prevention.
An ultraviolet-radiation-independent pathway to melanoma carcinogenesis in the red hair/fair skin background.
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