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

描述（由申请人提供）：在本补品的母体申请R01CA123055中，我们描述了具体的目标，以确定(i)使用DMB/TPA和UV-B协议，哪种细胞类型的COX-2必须表达才能诱导皮肤癌，以及（ii）哪种细胞类型的COX-2过表达可以调节皮肤癌的诱导。我们产生了“floxed”Cox2 （cox - 2flox）小鼠，其中Cox2的关键外显子两侧是loxP位点，以及COX-2条件过表达子（COX-2 COE）转基因小鼠，其中CAG启动子驱动COX-2蛋白表达。然而，在COX-2 COE小鼠中，CAG启动子与COX-2编码区通过一个封闭的转录/翻译STOP序列分离。我们计划通过将cox - 2flox小鼠与以组织特异性方式表达Cre重组酶的小鼠杂交，确定哪种细胞类型的COX-2必须在DMBA/TPA和/或UV-B诱导下表达。当皮肤上皮细胞中的Cox2基因被删除时（通过将Cox2小鼠与Keratin14CreTg小鼠杂交），DMBA/TPA皮肤肿瘤形成被广泛抑制。相反，我们认为，当巨噬细胞/单核细胞中的Cox2基因被删除时（通过将Cox2小鼠与LysMCreTg小鼠杂交），相对于对照组，皮肤肿瘤形成增加。COX-2介导的前列腺素（PG）在上皮细胞和单核/巨噬细胞中的形成在皮肤癌的发展中具有明显不同的作用。

DESCRIPTION (provided by applicant): In the parent application for this supplement, R01CA123055, we described specific aims to determine (i) in which cell type(s) COX-2 must be expressed for skin cancer induction, using the DMB/TPA and UV-B protocols, and (ii) in which cell type(s) skin cancer induction can be modulated by COX-2 over expression. We generated "floxed" Cox2 (Cox2flox) mice in which critical Cox2 exons are flanked by loxP sites and COX-2 conditional over expresser (COX-2 COE) transgenic mice in which the CAG promoter drives COX-2 protein expression. However, the CAG promoter is separated from the COX-2 coding region by a floxed transcription/translation STOP sequence in the COX-2 COE mouse. We planned to determine, by crossing Cox2flox mice with mice that express Cre recombinase in a tissue specific fashion, in which cell type(s) COX-2 must be expressed for skin cancer induction by DMBA/TPA and/or UV-B. When the Cox2 gene is deleted in skin epithelial cells (by crossing Cox2flox mice with Keratin14CreTg mice) DMBA/TPA skin tumor formation is extensively inhibited. In contrast - and surprisingly, we think - when the Cox2 gene is deleted in macrophage/monocytes (by crossing Cox2flox mice with LysMCreTg mice) skin tumor formation is increased, relative to littermate controls. COX-2 mediated prostaglandin (PG) formation in epithelial cells and in monocyte/macrophages has distinctly different roles in skin cancer development. In light of our data demonstrating distinct roles for COX-2 mediated PG expression in different cells during skin cancer progression, we add a third goal in this supplement application: We wish to ask "Can COX-2 expression in a single cell type, from the endogenous Cox2 promoter, mediate/modulate DMBA/TPA or UV-B induced skin cancer?" For example, can "endogenous" COX-2 expression from epithelial cells, without COX-2 expression in other cells, suffice for DMBA/TPA skin cancer induction? To answer this question we will develop Cox2 cell-restricted (Cox2Cr) mice in which the endogenous Cox2 gene is functionally silenced, unless a suppressing STOP sequence is removed by cell type-specific Cre excision. PUBLIC HEALTH RELEVANCE: 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 for COX-2 cancer enhancement and suppression.