Dioxin and Keratinocyte Differentiation

描述（申请人提供）：2,3,7,8，四氯二苯并-对二恶英 \(TCDD\)是一种普遍存在的促进肿瘤发生的环境污染物 通过被认为涉及的行为形成和调节细胞分化 芳烃受体（AHR）信号通路。考虑到 角化细胞分化已被证明提供了重要的见解 肿瘤启动子发挥作用的机制以及该模型的有效性 是适用于一些分子技术，我们已经开始研究 以实现我们理解TCDD作用的长期目标 在癌变中。使用正常的人角质形成细胞（NHK），我们已经证明了这一点 TCDD对NHK细胞的作用最终导致抑制 分化和这种影响是伴随着降低水平的 肿瘤抑制蛋白，p27Kipl 3‘-甲氧基-4’硝基黄酮暗示AHR在TCDD的介导中起作用 抑制分化。最后，很明显TCDD抑制 通过减少分化细胞的数量来实现分化 增加非分化细胞的数量。这些结果和其他结果， 形成了我们整体假设的基础，即TCDD的抑制能力 分化是由肿瘤表达水平的降低介导的 抑制蛋白p27Kipl，从而减少p27Kipl的分化 信号。为了验证这一假设，我们将使用流式细胞术，western blot 分析，实时PCR和腺病毒介导的过表达系统 确定：1)TCDD抑制分化的能力需要 2) TCDD调控p27Kipl蛋白 在转录或转录后水平，3)TCDD的能力 抑制p27Kipl的表达和分化需要AHR和 4) TCDD对分化的抑制导致了 5) TCDD对分化的作用发生在 基因组水平。

DESCRIPTION (provided by applicant): 2,3,7,8,Tetrachlorodibenzo-p-dioxin \(TCDD\) is a ubiquitous environmental contaminant that promotes tumor formation and modulates cellular differentiation via actions thought to involve the aryl hydrocarbon receptor (AHR) signaling pathway. Given that study of keratinocyte differentiation has been shown to lend important insights into the mechanism(s) by which tumor promoters exert their effects and that this model is amenable to a number of molecular techniques, we have initiated studies of differentiation to fulfill our long-term goal of understanding the role of TCDD in carcinogenesis. Using normal human keratinocytes (NHK), we have shown that administration of TCDD to NHK cells ultimately results in suppression of differentiation and that this effect is accompanied by decreased levels of the tumor suppressor protein, p27Kipl Additional studies using the ARR antagonist, 3'-methoxy-4'nitroflavone implied a role of the AHR in mediating TCDD's suppression of differentiation. Finally, it is apparent that TCDD suppresses differentiation by decreasing the number of differentiating cells while increasing the number of non-differentiating cells. These results and others, form the basis of our overall hypothesis that the ability of TCDD to suppress differentiation is mediated by a decrease in the expression levels of the tumor suppressor protein, p27Kipl thereby diminishing the p27Kipl differentiation signal. To test this hypothesis, we will use flow cytometry, western blot analysis, real time PCR and adenovirus-mediated over expression systems to determine whether: 1) the ability of TCDD to suppress differentiation requires suppression of the expression of p27Kipl, 2) TCDD regulates the p27Kipl protein at the transcriptional or post-transcriptional levels, 3) the ability of TCDD to suppress the expression of p27Kipl and differentiation requires the AHR and ARNT proteins, 4) suppression of differentiation by TCDD results in increased) proliferation, and 5) and the actions of TCDD on differentiation occur at the) genomic level.