Wang X J, Greenhalgh D A, Jiang A, He D, Zhong L, Brinkley B R, Roop D R
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Mol Carcinog. 1998 Nov;23(3):185-92. doi: 10.1002/(sici)1098-2744(199811)23:3<185::aid-mc7>3.0.co;2-5.
We previously developed a transgenic mouse model that expresses in the epidermis a murine p53172R-->H mutant (p53m) under the control of a human keratin-1-based vector (HK1.p53m). In contrast to mice with wild-type p53 and p53-knockout mice, HK1.p53m mice exhibit increased susceptibility to chemical carcinogenesis, with greatly accelerated benign papilloma formation, malignant conversion, and metastasis. In the study presented here, we examined the expression pattern of several differentiation markers and observed that p53m tumors exhibited a less differentiated phenotype than tumors elicited in non-transgenic mice. Metastasis in p53m tumors was also associated with a poorly differentiated phenotype. To determine whether genomic instability was associated with a putative gain-of-function role for this p53m, in situ examination of centrosomes was performed in HK1.p53m and equivalent p53-null papillomas. In contrast to HK1.p53m papillomas, which had centrosome abnormalities at high frequencies (75% of cells contained more than three centrosomes/cell), p53-null tumors exhibited few abnormal centrosomes (4% of cells contained more than three centrosomes/cell). To determine whether angiogenesis played a role in the rapid progression of p53m tumors, the expression of vascular endothelial growth factor, a promoter of angiogenesis, and thrombospondin-1, an inhibitor of angiogenesis, was examined in tumors derived from either p53m or p53-knockout mice. Regardless of their p53 status (wild type, p53m, p53-/-), all of the papillomas exhibited similar levels of vascular endothelial growth factor expression and decreased expression of thrombospondin-1 as did normal epidermis. In addition, tumors from different p53 genotypes showed a similar density of blood vessels. Because p53 status did not appear to play an overt role in angiogenesis, these data suggest that p53m accelerates tumorigenesis primarily by exerting a gain of function associated with genomic instability.
我们之前构建了一种转基因小鼠模型，该模型在人角蛋白-1载体（HK1.p53m）的控制下，在表皮中表达鼠源p53172R→H突变体（p53m）。与野生型p53小鼠和p53基因敲除小鼠相比，HK1.p53m小鼠对化学致癌作用的易感性增加，良性乳头瘤形成、恶性转化和转移大大加速。在本研究中，我们检测了几种分化标志物的表达模式，发现p53m肿瘤表现出比非转基因小鼠诱发的肿瘤分化程度更低的表型。p53m肿瘤中的转移也与低分化表型相关。为了确定基因组不稳定性是否与这种p53m的假定功能获得作用相关，我们在HK1.p53m和等效的p53基因敲除乳头瘤中进行了中心体的原位检测。与HK1.p53m乳头瘤不同，HK1.p53m乳头瘤中中心体异常的频率很高（75%的细胞含有超过三个中心体/细胞），而p53基因敲除肿瘤中很少有异常中心体（4%的细胞含有超过三个中心体/细胞）。为了确定血管生成是否在p53m肿瘤的快速进展中起作用，我们检测了血管内皮生长因子（一种血管生成促进因子）和血小板反应蛋白-1（一种血管生成抑制剂）在来自p53m或p53基因敲除小鼠的肿瘤中的表达。无论其p53状态（野生型、p53m、p53-/-）如何，所有乳头瘤的血管内皮生长因子表达水平都与正常表皮相似，血小板反应蛋白-1的表达降低。此外，来自不同p53基因型的肿瘤显示出相似的血管密度。由于p53状态在血管生成中似乎没有明显作用，这些数据表明p53m主要通过发挥与基因组不稳定性相关的功能获得作用来加速肿瘤发生。
