It is well established that exposure to sunlight or ultraviolet radiation (UVR) is the major environmental risk factor for the development of
skin neoplasms. To date, however, there have been few appropriate mouse models available for studying the role of UVR in
melanoma carcinogenesis, mainly because of the murine lack of the epidermal melanocyte, which is a major source of origin of human
melanoma. In this study, we established
xeroderma pigmentosum group A gene-deficient,
stem cell factor-transgenic mice, which are defective in the repair of damaged
DNA and do have epidermal melanocytes. The mice were exposed to UVR three times a week for 10 wk. More than 30% of the irradiated mice developed
tumors of melanocyte origin that metastasized to the lymph nodes. Histologically, proliferated cells exhibited
lentigo maligna melanoma or nodular
melanoma. Immunohistochemistry confirmed that the
tumor cells were characteristic of
melanoma. Non-irradiated mice did not develop skin
tumors spontaneously. The newly generated model mouse might be useful for studying the photobiological aspects of human
melanoma, because the mice developed
melanoma from epidermal melanocytes only after UVR exposures.