Germolec D R, Spalding J, Boorman G A, Wilmer J L, Yoshida T, Simeonova P P, Bruccoleri A, Kayama F, Gaido K, Tennant R, Burleson F, Dong W, Lang R W, Luster M I
Environmental Immunology and Neurobiology Section, NIH, Research Triangle Park, NC 27709, USA.
Mutat Res. 1997 Jun;386(3):209-18. doi: 10.1016/s1383-5742(97)00006-9.
Although numerous epidemiological studies have shown that inorganic arsenicals are human skin carcinogens, there is currently no accepted mechanism for its action or an established animal model for its study. We observed increased mRNA transcripts and secretion of keratinocyte growth factors, including granulocyte macrophage-colony stimulating factor (GM-CSF) and transforming growth factor-alpha (TGF-alpha) and the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) in primary human epidermal keratinocytes cultured in the presence of low micromolar concentrations of sodium arsenite. Total cell numbers, as well as c-myc expression and incorporation of [3H]thymidine, both indicators of cell proliferation, were also elevated in keratinocyte cultures treated with sodium arsenite. As an in vivo model, the influence of arsenic on mouse skin tumor development was studied in transgenic TG.AC mice which carry the v-Ha-ras oncogene, and can serve as a genetically initiated model for skin carcinogenesis. Following low-dose application of 12-O-tetradecanoyl phorbol-13-acetate (TPA), a marked increase in the number of skin papillomas occurred in transgenic mice receiving arsenic in the drinking water as compared to control drinking water. Papillomas did not develop in arsenic-treated transgenic mice that had not received TPA or arsenic-treated wild-type FVB/N mice, suggesting that arsenic is neither a tumor initiator or promoter but rather an enhancer. Injection of anti-GM-CSF antibodies following application of TPA in transgenic mice reduced the number of papillomas. Consistent with that observed in human keratinocyte cultures, increases in GM-CSF and TGF-alpha mRNA transcripts were found within the epidermis of arsenic-treated mice when compared to controls within 6 weeks of treatment. These results suggest that arsenic enhances papilloma development via the chronic stimulation of keratinocyte-derived growth factors and represents the first example of a chemical carcinogen that acts in this manner. These studies suggest that in vitro studies with human keratinocyte cultures examined in conjunction with TG.AC transgenic mice can provide a useful model for examining the tumor enhancing properties of environmental chemicals.
尽管众多流行病学研究表明无机砷是人类皮肤致癌物，但目前尚无其作用的公认机制，也没有用于研究的成熟动物模型。我们观察到，在含有低微摩尔浓度亚砷酸钠的培养基中培养的原代人表皮角质形成细胞中，角质形成细胞生长因子的mRNA转录物和分泌增加，这些生长因子包括粒细胞巨噬细胞集落刺激因子（GM-CSF）、转化生长因子-α（TGF-α）以及促炎细胞因子肿瘤坏死因子-α（TNF-α）。细胞总数以及作为细胞增殖指标的c-myc表达和[3H]胸腺嘧啶掺入量，在用亚砷酸钠处理的角质形成细胞培养物中也有所升高。作为体内模型，在携带v-Ha-ras癌基因的转基因TG.AC小鼠中研究了砷对小鼠皮肤肿瘤发生的影响，该小鼠可作为皮肤癌发生的遗传启动模型。在低剂量应用12-O-十四酰佛波醇-13-乙酸酯（TPA）后，与饮用对照水的转基因小鼠相比，饮用含砷水的转基因小鼠皮肤乳头瘤数量显著增加。未接受TPA的砷处理转基因小鼠或砷处理的野生型FVB/N小鼠均未发生乳头瘤，这表明砷既不是肿瘤启动剂也不是促进剂，而是一种增强剂。在转基因小鼠中应用TPA后注射抗GM-CSF抗体可减少乳头瘤数量。与在人角质形成细胞培养物中观察到的结果一致，与处理6周内的对照相比，在砷处理小鼠的表皮内发现GM-CSF和TGF-α mRNA转录物增加。这些结果表明，砷通过对角质形成细胞衍生生长因子的慢性刺激增强乳头瘤的发生，这是化学致癌物以这种方式作用的首个实例。这些研究表明，结合TG.AC转基因小鼠进行的人角质形成细胞培养体外研究可为检测环境化学物质的肿瘤增强特性提供有用模型。
