GR Impairment in Carconogenesis: Tumor Suppressor Role

描述（由申请人提供）：糖皮质激素是体内角质形成细胞生理DNA合成的非常有效的抑制剂。当与致癌物或肿瘤促进剂一起应用于皮肤时，这些激素在预防致癌物和肿瘤促进剂诱导的皮肤增生、炎症和小鼠皮肤肿瘤形成方面也非常有效。然而，我们和其他人已经表明，糖皮质激素不影响已建立的乳头状瘤，鳞状细胞癌（SCC）或转化的角质形成细胞在体外的生长。此外，我们最近发现，糖皮质激素净影响糖皮质激素反应基因在转化角质形成细胞在体外/和在体内。糖皮质激素对细胞功能的控制是由糖皮质激素受体（GR）介导的，GR是一种众所周知的转录因子。我们已经发现NF-κ B转录因子在小鼠皮肤肿瘤中被组成性激活，这似乎改变了GR的一些功能。我们还发现NF-κ B的这种激活主要是由于SCFmHOS泛素连接酶的上调。我们已经产生了皮肤靶向的转基因小鼠过表达GR角蛋白5（K5）启动子的控制下。这些成年转基因小鼠对皮肤肿瘤促进剂的增殖和炎症反应受损。我们的初步研究表明，K5.GR转基因动物对I-as诱导的肿瘤发生具有抗性。在K5.GR/ras+双转基因小鼠中，表皮中GR的组成性核过表达和激活显著抑制了皮肤肿瘤的发展，这与发展肿瘤的动物数量、每只动物的肿瘤数量和肿瘤大小有关。我们提出的假设，GR功能作为一种肿瘤抑制剂在小鼠皮肤癌的发生。根据这一目标，具体的目标是：1）开发皮肤中GR表达缺陷的动物，并分析其对皮肤癌变的敏感性。2)确定GR的反式阻遏活性是否足以抑制小鼠皮肤乳头状瘤和癌细胞系的致瘤性。3)为了确定GR发挥肿瘤抑制因子作用的致癌阶段，a）开发皮肤中有条件表达GR的转基因动物（TRE.GR X K5.Tet-On）。B）当在肿瘤发展的不同阶段诱导GR的过表达时，分析这些小鼠对皮肤癌发生的敏感性。4)分析游离糖皮质激素对皮肤炎症、角质形成细胞增殖和皮肤肿瘤发生的影响。

DESCRIPTION (provided by applicant): Glucocorticoid hormones are very potent inhibitors of physiological DNA synthesis in keratinocytes in vivo. These hormones are also very effective in preventing carcinogen- and tumor promoter-induced skin hyperplasia, inflamination, and mouse skin tumor formation when applied to skin together with a carcinogen or a tumor promoter. We and others have shown, however, that glucocorticoids do not affect the growth of either established papillomas, squamous ceil carcinomas (SCC), or transformed keratinocytes in vitro. In addition, we recently found that glucocorticoids do net affect glucocorticoid-responsive genes in transformed keratinocytes both; in vitro/and in vivo. The glucocorticoid control of cellular functions is mediated by the glucocorticoid receptor (GR), a well-known transcription factor. We have found that NF-KB transcription factor is constitutively activated in mouse skin tumors which appears to alter some of GR functions. We have also found that this activation of NF-KB is primarily due to up-regulation of SCFmHOS ubiquitin ligase. We have generated skin-targeted transgenic mice over-expressing GR under the control of keratin 5 (K5) promoter. These adult transgenic mice have impaired proliferative and inflammatory responses to skin tumor promoters. Our initial studies showed that K5.GR transgenic animals are resistant to /-as-induced tumorigenesis. The constitutively nuclear overexpression and activation of GR in the epidermis dramatically inhibited skin tumor development in K5.GR/ras+ double transgenic mice in terms of number of animals that develop tumors, number of tumors per animal, and tumor size. We propose to prove the hypothesis that GR functions as a tumor suppressor in mouse skin carcinogenesis. Pursuant to this goal, the specific aims are: 1) To develop animals deficient in the expression of GR in skin, and analyze their sensitivity to skin carcinogenesis. 2) To determine whether transrepression activities of GR are sufficient to suppress tumorigenic properties of mouse skin papilloma and carcinoma cell lines. 3) To determine the stage(s) of carcinogenesis where GR plays a role of tumor suppressor a) develop transgenic animals with the conditional expression of GR in skin (TRE.GR X K5.Tet-On). b) analyze the sensitivity of these mice to skin carcinogenesis, when over-expression of GR induced at different stages of tumor development. 4) To analyze the effects of dissociated glucocorticoids on skin inflammation, keratinocyte proliferation, and on skin tumor development.