Preroxisome Proliferator-Activated Receptors in lung Cancer

描述（由申请人提供）：过氧化物酶体增殖物激活受体（PPAR）是核激素受体超家族的成员，作为配体激活的转录因子。已鉴定出三种亚型，即PPAR α、γ和δ，所有这些亚型均与视黄酸X受体作为异源二聚体结合到特异性DNA序列上。已显示，PPARgamma可被合成的抗糖尿病噻唑烷二酮类（TZD）（如环格列酮和曲格列酮）以及可作为内源性激活剂发挥作用的前列腺素D和J衍生物激活。虽然PPARgamma在脂肪细胞分化中的重要作用已被确定，但该分子在包括非小细胞肺癌细胞（NSCLC）在内的多种细胞类型中表达。来自我们实验室和其他研究者的数据表明，PPARgamma激活剂抑制NSCLC的转化生长。然而，这些药物参与其他途径，并且在其他类型的癌症中获得了相互矛盾的数据，表明PPARs的促肿瘤和抗肿瘤作用。PPARdelta已被前列环素及其稳定类似物伊洛前列素激活。PPARdelta在癌症发展中的作用也不清楚，研究证明了致瘤和抗致瘤作用。我们实验室的初步研究表明，PPARgamma在多种NSCLC细胞系中的过表达选择性抑制了体外软琼脂中的锚定非依赖性生长，以及异种移植模型中肺肿瘤的发展。使用微阵列的基因表达分析表明，这些抑制作用可能是通过改变整合素和酶的表达，调节细胞外基质，涉及细胞迁移和侵袭的改变介导的。NSCLC中PPARdelta的过表达抑制PPARgamma活性并导致软琼脂集落形成增加。对于这两种亚型的过氧化物酶体增殖物激活受体的分子机制，从而调节肺肿瘤的发生知之甚少。本提案的目的是采用分子和药理学方法来验证特定PPAR亚型的激活对肺癌发展具有相反作用的假设，并确定可能解释这些作用的潜在机制。提出了四个具体目标。具体目标1将检查过表达PPARgamma和δ对NSCLC细胞系转化生长的影响，并将反应与推定的特异性药理学试剂的作用进行比较。具体目标2将使用二维和三维组织培养来定义PPARs过表达对细胞形态、迁移和分化诱导的分子变化。特定目标3将开发特异性过表达PPARs的转基因小鼠，并评估其在致癌模型中的作用。具体目标4将使用来自人肺癌样本的组织微阵列检查PPAR表达。这些研究将有助于确定PPARs在肺肿瘤发生中的作用，并有助于确定治疗干预的新靶点。

DESCRIPTION (provided by applicant): Peroxisome proliferator-activated receptors (PPAR) are members of the nuclear hormone receptor superfamily which act as ligand-activated transcription factors. Three isoforms have been identified, PPAR alpha, gamma, and delta, all of which bind to specific DNA sequences as heterodimers with the retinoic acid X-receptors. PPARgamma has been shown to be activated by the synthetic antidiabetic thiazolidinediones (TZD) such as ciglitazone and troglitazone as well as by prostaglandin D and J derivatives which may function as endogenous activators. While an important role for PPARgamma has been defined in adipocyte differentiation, this molecule is expressed in a variety of cell types including non-small cell lung cancer cells (NSCLC). Data from our laboratory and other investigators have shown that activators of PPARgamma inhibit transformed growth of NSCLC. However, these agents engage additional pathways, and conflicting data has been obtained in other types of cancer, indicating both a pro- and anti-tumorigenic role for PPARs. PPARdelta has been shown to be activated by prostacyclin and its stable analog iloprost. The role of PPARdelta in the development cancer is also not clear, with studies demonstrating both a tumorigenic and anti-tumorigenic role. Preliminary studies from our laboratory have shown that overexpression of PPARgamma in multiple NSCLC lines selectively inhibited anchorage-independent growth in soft agar in vitro, and the development of lung tumors in xenograft models. Analysis of gene expression using microarrays suggests that these inhibitory effects may be mediated through altered expression of integrins and enzymes that modulate extracellular matrix, implicating alterations in cell migration and invasion. Overexpression of PPARdelta in NSCLC inhibits PPARgamma activity and leads to increased soft agar colony formation. For both isoforms of PPAR the molecular mechanisms whereby PPARs regulate lung tumorigenesis are poorly understood. The goal of this proposal is to employ molecular and pharmacological approaches to test the hypothesis that activation of specific PPAR isoforms has opposing effects on the development of lung cancer, and to identify potential mechanisms which may account for these effects. Four specific aims are proposed. Specific aim 1 will examine the effects of overexpressing PPARgamma and delta on the transformed growth of NSCLC lines, and compare the response with effects of putative specific pharmacological agents. Specific Aim 2 will define the molecular changes induced by overexpression of PPARs on cell morphology, migration and differentiation, using 2-dimensional and three dimensional tissue culture. Specific Aim 3 will develop transgenic mice specifically overexpressing PPARs, and assess their role in carcinogenesis models. Specific Aim 4 will examine PPAR expression using a tissue microarray derived from human lung cancer samples. These studies will help to define the role of PPARs in lung tumorigenesis, and help to define new targets for therapeutic intervention.