Peroxisome Proliferator Activated Receptors in Lung Cancer

描述(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，其作用是配体激活的转录因子。已鉴定出三种异构体，PPARα、γ和Delta，它们都以异源二聚体的形式与特定的DNA序列结合，并与维甲酸X受体结合。合成的抗糖尿病药(TZD)如环格列酮和曲格列酮以及前列腺素D和J的衍生物可能作为内源性激活剂被激活。虽然PPARGamma在脂肪细胞分化中起着重要作用，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都有表达。我们实验室和其他研究人员的数据表明，PPARγ激活剂可以抑制非小细胞肺癌的转化生长。然而，这些药物参与了其他途径，在其他类型的癌症中获得了相互矛盾的数据，表明PPAR既有促肿瘤作用，也有抗肿瘤作用。前列环素及其稳定的类似物伊洛前列素可激活PPAR Delta。PPARDelta在癌症发生发展中的作用也不清楚，研究表明它既有致癌作用，也有抗肿瘤作用。我们实验室的初步研究表明，在多个非小细胞肺癌细胞系中过表达PPARγ，在体外选择性地抑制软琼脂中的锚定非依赖性生长，并在异种移植模型中抑制肺肿瘤的发展。利用微阵列对基因表达的分析表明，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PPARDelta抑制PPARGamma活性，并导致软琼脂集落形成增加。对于这两种PPAR亚型，PPAR调控肺肿瘤发生的分子机制还知之甚少。这项建议的目的是利用分子和药理学方法来检验特定的PPAR亚型的激活对肺癌的发展具有相反的影响的假设，并确定可能解释这些影响的潜在机制。提出了四个具体目标。具体目标1将检测过表达PPARγ和Delta对非小细胞肺癌细胞系转化生长的影响，并将其反应与假定的特定药理药物的效果进行比较。具体目标2将利用二维和三维组织培养，定义PPAR过表达对细胞形态、迁移和分化的分子变化。特指目标3将开发专门过度表达PPAR的转基因小鼠，并评估它们在致癌模型中的作用。特定目标4将使用从人类肺癌样本中提取的组织微阵列来检测PPAR的表达。这些研究将有助于确定PPAR在肺肿瘤发生中的作用，并有助于为治疗干预定义新的靶点。

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.