The role of epidermal, fibroblast and endothelial cell COX-2 in skin cancer

描述(由申请人提供)：临床证据、流行病学结果和实验动物研究压倒性地表明，COX-2的过度表达在许多上皮性癌症的发展中起调节甚至因果作用。最近的研究表明，间质成纤维细胞和血管内皮细胞调节上皮性肿瘤的形成。也有大量的相关数据表明，COX-2在间质成纤维细胞和血管内皮细胞中的表达--而不是在启动的上皮性肿瘤前体细胞中--可能参与了上皮性癌的癌前病变和随后的进展。然而，现有的COX-2药理学实验和全球COX-2基因敲除小鼠不允许进行生理学或遗传学分析来确定特定的细胞群体-成纤维细胞、上皮细胞或血管内皮细胞-在其中COX-2过表达在肿瘤发生中起关键作用(S)。我们已经发展出(I)COX2COE转基因小鼠，在其中我们可以在靶细胞和组织中有条件地过表达COX-2；(Ii)在Cox2flx小鼠中，我们可以在靶细胞和组织中有条件地删除COX2基因。通过将COX2 COE小鼠和Cox2flx小鼠杂交到转基因小鼠，在转基因小鼠中，他莫昔芬调控的CreERT重组酶在上皮细胞、间质成纤维细胞或血管内皮细胞中表达，我们将能够确定(1)是否在上皮细胞、成纤维细胞和/或血管内皮细胞中过量表达COX-2参与调节癌症的发生；(2)在癌症的发生发展过程中是否需要在上皮细胞、成纤维细胞或血管内皮细胞中表达COX-2。皮肤癌是研究最多的上皮性肿瘤诱导模型之一。我们选择皮肤癌来研究COX-2在上皮细胞、间质成纤维细胞和血管内皮细胞中的作用(S)，因为关于这一模型的文献很多，肿瘤易于非侵袭性地监测，并且CreERT容易被局部激活。本应用的“广泛的、长期的目标和具体的目标”是确定(1)COX-2是否在上皮性肿瘤的发生发展中起调控和/或必需的作用(S)，以及(2)在哪个细胞(S)启动的上皮性肿瘤前体细胞和/或间质成纤维细胞和/或血管内皮细胞-COX-2调控上皮癌前病变或良性肿瘤向癌症的进展中。这项研究与公共卫生的相关性。环氧合酶-2抑制剂仍然被研究为治疗和预防上皮性癌症的药物，尽管有心血管副作用。“下游”环氧合酶-2途径效应物(前列腺素合成酶和受体)已成为类似研究的目标。如果我们能够准确地确定COX-2表达和前列腺素类效应分子调控癌症发展的细胞类型(S)，我们可能能够以较低的浓度和较短的药理药物应用时间来针对这些步骤。我们预计我们将能够确定COX-2癌症增强的关键细胞和时间。

DESCRIPTION (provided by applicant): Clinical evidence, epidemiological results and experimental animal studies overwhelmingly suggest that COX-2 over-expression plays a modulatory and even causal role in development of many epithelial cancers. Recent studies demonstrate that stromal fibroblasts and blood vessel endothelial cells modulate epithelial tumor formation. There also exist substantial correlative data suggesting that COX-2 expression in stromal fibroblasts and blood vessel endothelial cells - and not in the initiated epithelial tumor precursor cells - may mediate pre-neoplastic emergence and subsequent progression of epithelial cancers. However, existing COX-2 pharmacologic experiments and global Cox2 knockout mice do not permit either physiological or genetic analyses to determine the specific cell populations - fibroblasts, epithelial or blood vessel endothelial cells - in which COX-2 over expression plays a critical role(s) in tumor development. We have developed (i) COX2 COE transgenic mice, in which we can conditionally over-express COX-2 in targeted cells and tissues and (ii) Cox2flox mice, in which we can conditionally delete the Cox2 gene in targeted cells and tissues. By crossing COX2 COE mice and Cox2flox mice to transgenic mice in which a tamoxifen-regulated CreERT recombinase is expressed in either epithelial cells, stromal fibroblasts or blood vessel endothelial cells, we will be able to determine (1) whether COX-2 over production in epithelial cells, fibroblasts and/or blood vessel endothelial cells modulates cancer development and (2) whether COX-2 expression is required in epithelial cells, fibroblasts or blood vessel endothelial cells for cancer development. Skin cancer is among the best-studied epithelial tumor induction models. We chose skin cancer to study the role(s) of COX-2 in epithelial cells, stromal fibroblasts and blood vessel endothelial cells during development of epithelial cancer because of the extensive literature on this model, the ease with which tumors can be monitored non-invasively, and the ease with which CreERT can be activated locally. The "broad, long-term objectives and specific aims" of this application are to determine (1) whether COX-2 plays a modulatory and/or a required role(s) in development of epithelial cancer and (2) in which cell(s) - initiated epithelial tumor precursor cell and/or stromal fibroblast and/or blood vessel endothelial cell - COX-2 modulates either pre-malignant epithelial tumor development or progression of benign tumors to carcinomas. The relevance of this research to public health. COX-2 inhibitors are still investigated as therapeutic and preventive agents for epithelial cancers, despite cardiovascular side effects. "Down-stream" COX-2 pathway effectors (prostanoid synthases and receptors) have become targets for similar research. If we can pinpoint the cell type(s) in which COX-2 expression and the prostanoid effectors regulate cancer development, we may be able to target those steps with lower concentrations and less prolonged application of pharmacologic agents. We anticipate we will be able to define the critical cells and times for COX-2 cancer enhancement.