Battalora M S, Spalding J W, Szczesniak C J, Cape J E, Morris R J, Trempus C S, Bortner C D, Lee B M, Tennant R W
Laboratory of Environmental Carcinogenesis and Mutagenesis, National Institute of Environmental Health Sciences, PO Box 12233, Research Triangle Park, NC 27709, USA.
Carcinogenesis. 2001 Apr;22(4):651-9. doi: 10.1093/carcin/22.4.651.
Transgenic Tg.AC (v-Ha-ras ) mice develop skin tumors in response to specific carcinogens and tumor promoters. The Tg.AC mouse carries the coding sequence of v-Ha ras, linked to a zeta-globin promoter and an SV40 polyadenylation signal sequence. The transgene confers on these mice the property of genetically initiated skin. This study examines the age-dependent sensitivity of the incidence of skin papillomas in Tg.AC mice exposed to topically applied 12-O:-tetradecanoylphorbol-13-acetate (TPA) treatment, full thickness skin wounding or UV radiation. Skin tumor incidence and multiplicity were strongly age-dependent, increasing with increasing age of the animal when first treated at 5, 10, 21 or 32 weeks of age. Furthermore, the temporal induction of transgene expression in keratinocytes isolated from TPA-treated mouse skin was also influenced by the age of the mice. Transgene expression was seen as early as 14 days after the start of TPA treatment in mice that were 10-32 weeks of age, but was not detected in similarly treated 5-week old mice. When isolated keratinocytes were fractionated by density gradient centrifugation the highest transgene expression was found in the denser basal keratinocytes. Transgene expression could be detected in the denser keratinocyte fraction as early as 9 days from start of TPA treatment in 32-week old mice. Using flow cytometry, a positive correlation was observed between expression of the v-Ha-ras transgene and enriched expression of the cell surface protein beta1-integrin, a putative marker of epidermal stem cells. This result suggests that, in the Tg.AC mouse, an age-dependent sensitivity to tumor promotion and the correlated induction of transgene expression are related to changes in cellular development in the follicular compartment of the skin.
转基因Tg.AC（v-Ha-ras）小鼠在接触特定致癌物和肿瘤启动剂时会发生皮肤肿瘤。Tg.AC小鼠携带v-Ha ras的编码序列，该序列与ζ-珠蛋白启动子和SV40多聚腺苷酸化信号序列相连。转基因赋予这些小鼠遗传性起始皮肤的特性。本研究考察了经局部涂抹12-O-十四烷酰佛波醇-13-乙酸酯（TPA）处理、全层皮肤创伤或紫外线辐射的Tg.AC小鼠皮肤乳头瘤发生率的年龄依赖性敏感性。皮肤肿瘤发生率和多发性具有强烈的年龄依赖性，当在5、10、21或32周龄首次处理时，随着动物年龄的增加而增加。此外，从经TPA处理的小鼠皮肤中分离出的角质形成细胞中转基因表达的时间诱导也受小鼠年龄的影响。在10 - 32周龄的小鼠中，TPA处理开始后14天就可观察到转基因表达，但在同样处理的5周龄小鼠中未检测到。当通过密度梯度离心分离角质形成细胞时，在密度较大的基底角质形成细胞中发现最高的转基因表达。在32周龄小鼠中，从TPA处理开始9天就可在密度较大的角质形成细胞部分检测到转基因表达。使用流式细胞术，观察到v-Ha-ras转基因表达与细胞表面蛋白β1整合素（一种假定的表皮干细胞标志物）的富集表达之间呈正相关。这一结果表明，在Tg.AC小鼠中，对肿瘤促进的年龄依赖性敏感性和转基因表达的相关诱导与皮肤毛囊区室细胞发育的变化有关
