UV Irradiation Does Not Genetically Alter Melanocytes
The effects of UV irradiation on melanocytes are not fully understood. Previous research has shown that UV irradiation leads to histologic changes reminiscent of melanoma in situ, such as intraepidermal melanocyte atypia, and increased numbers of single melanocytes above the dermal-epidermal junction. In addition, certain genetic changes are known to occur in atypical nevi, which are the presumptive precursor lesions of melanoma. In this study, researchers genetically analyzed irradiated nevi to look for similar DNA derangements in affected melanocytes.
Seven symmetrical, benign nevi were chosen for examination. Half of each nevus was shielded, and the other half was exposed to UV irradiation at four times the patient's minimal erythema dose. One week later, each nevus was removed and DNA was extracted. Probes for various loci associated with melanomas and melanoma precursors (1p, 9q, and 9p21) were applied to treated and untreated nevi. No allelic losses were found in any of the nevi. The researchers concluded that, although the histologic changes in melanocytic nevi after UV exposure resemble melanoma in situ, they are not followed by similar alterations in melanocytic DNA.
Comment: As the researchers suggest, the one-week time interval between UV exposure and DNA examination may not have been sufficient for loss of genetic heterozygosity, and the irradiation doses may not have been large enough to induce detectable changes. It is also possible that the changes in melanocytes induced by UV exposure are transient and do not lead to permanent genetic alterations.
Published in Journal Watch Dermatology September 1, 1998
Böni R et al. Ultraviolet-induced acute histological changes in irradiated nevi are not associated with allelic loss. Arch Dermatol 1998 134 853-856.
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