Setlow R B, Grist E, Thompson K, Woodhead A D
Biology Department, Brookhaven National Laboratory, Upton, NY 11973.
Proc Natl Acad Sci U S A. 1993 Jul 15;90(14):6666-70. doi: 10.1073/pnas.90.14.6666.
It is generally agreed that sunlight exposure is one of the etiologic agents in malignant melanoma of fair-skinned individuals. However, the wavelengths responsible for tumorigenesis are not known, although DNA is assumed to be the target because individuals defective in the repair of UV damage to DNA are several thousandfold more prone to the disease than the average population. Heavily pigmented backcross hybrids of the genus Xiphophorus (platyfish and swordtails) are very sensitive to melanoma induction by single exposures to UV. We irradiated groups of five 6-day-old fish with narrow wavelength bands at 302, 313, 365, 405, and 436 nm and scored the irradiated animals for melanomas 4 months later. We used several exposures at each wavelength to obtain estimates of the sensitivity for melanoma induction as a function of exposure and wavelength. The action spectrum (sensitivity per incident photon as a function of wavelength) for melanoma induction shows appreciable sensitivity at 365, 405, and probably 436 nm, suggesting that wavelengths not absorbed directly in DNA are effective in induction. We interpret the results as indicating that light energy absorbed in melanin is effective in inducing melanomas in this animal model and that, in natural sunlight, 90-95% of melanoma induction may be attributed to wavelengths > 320 nm--the UV-A and visible spectral regions.
人们普遍认为，暴露于阳光下是白皮肤个体患恶性黑色素瘤的病因之一。然而，尽管由于DNA被认为是靶点，因为DNA紫外线损伤修复存在缺陷的个体患该病的几率比普通人群高数千倍，但导致肿瘤发生的波长尚不清楚。剑尾鱼属（孔雀鱼和剑尾鱼）的深色回交杂种对单次紫外线照射诱导黑色素瘤非常敏感。我们用302、313、365、405和436纳米的窄波段对每组五条6日龄的鱼进行照射，并在4个月后对受照射的动物进行黑色素瘤评分。我们在每个波长下进行了几次照射，以获得黑色素瘤诱导敏感性随照射量和波长变化的估计值。黑色素瘤诱导的作用光谱（每入射光子的敏感性随波长变化）在365、405以及可能在436纳米处显示出明显的敏感性，这表明未直接被DNA吸收的波长在诱导中是有效的。我们将结果解释为表明在这种动物模型中，黑色素吸收的光能在诱导黑色素瘤方面是有效的，并且在自然阳光下，90 - 95%的黑色素瘤诱导可能归因于波长> 320纳米的区域——紫外线A和可见光谱区域。
