Preroxisome Proliferator-Activated Receptors in lung Cancer

描述（由申请人提供）：过氧化物酶体增殖激活受体（PPAR）是核激素受体超家族的成员，作为配体激活的转录因子。已经鉴定出PPAR α、γ和δ三种同工异构体，它们都与视黄酸x受体作为异源二聚体结合到特定的DNA序列上。PPARgamma被合成的抗糖尿病噻唑烷二酮（TZD）如西格列酮和曲格列酮以及可能作为内源性激活剂的前列腺素D和J衍生物激活。虽然PPARgamma在脂肪细胞分化中发挥重要作用，但该分子在多种细胞类型中表达，包括非小细胞肺癌细胞（NSCLC）。我们实验室和其他研究人员的数据表明，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ppar具有促肿瘤和抗肿瘤作用。PPARdelta已被证明可被前列环素及其稳定的类似物伊洛前列素激活。PPARdelta在癌症发展中的作用也不清楚，研究表明它既有致瘤作用，也有抗致瘤作用。我们实验室的初步研究表明，在多种NSCLC细胞系中，PPARgamma的过表达选择性地抑制了体外软琼脂中不依赖锚定的生长，以及异种移植模型中肺肿瘤的发展。基因表达的微阵列分析表明，这些抑制作用可能是通过改变整合素和调节细胞外基质的酶的表达来介导的，这意味着细胞迁移和侵袭的改变。在非小细胞肺癌中，过表达pparδ抑制pparγ活性，导致软琼脂集落形成增加。对于PPAR的两种亚型，PPAR调节肺肿瘤发生的分子机制尚不清楚。本研究的目的是利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。特异性目的1将检查过表达PPARgamma和delta对NSCLC细胞系转化生长的影响，并将其反应与假定的特异性药理学药物的作用进行比较。Specific Aim 2将利用二维和三维组织培养，定义PPARs过表达对细胞形态、迁移和分化的分子变化。Specific Aim 3将开发特异性过表达PPARs的转基因小鼠，并评估其在癌变模型中的作用。Specific Aim 4将使用来自人类肺癌样本的组织微阵列检测PPAR表达。这些研究将有助于确定ppar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.