A new strategy for the therapy of pancreatic cancer by a specific ligand of peroxisome proliferator-activated receptor-gamma

过氧化物酶体增殖物激活受体-γ(PPAR-γ)是核受体超家族的一种转录因子，与维甲酸X受体形成功能性异源二聚体。人工合成的PPAR-γ配体已被证明在体内外对几种人类肿瘤细胞株的生长具有抑制作用，并在人脂肪肉瘤、结肠癌和乳腺癌细胞的原代培养中诱导生长停滞和分化。本研究的目的是检测PPAR-γ是否在人胰腺癌细胞中高水平表达，以及其配体能否通过终末分化抑制胰腺癌细胞的生长。此外，我们还检测了噻唑烷二酮(TZD)，一个有效的PPAR-γ配体。可以调控人胰腺癌细胞中的E-钙粘蛋白/β-连环蛋白系统。首先，我们研究了PPAR-γ在五种胰腺癌细胞系中的表达：CAPAN-1(高分化腺癌)、ASPC-1(中分化腺癌…)更多的癌)、BxPC-3(中分化腺癌)、Panc-1(低分化腺癌)和MIAPaCa-2(未分化癌)。RT-γ和Western blotting分析显示5种细胞均表达PPAR-PPAR基因和蛋白。克隆形成试验表明，TZD在10μM时可完全抑制这些细胞的集落形成，10μM TZD可使G0/G1期细胞周期停滞。Western blotting显示，TZD明显增加分化标志物E-钙粘素和癌胚抗原，而β-连环蛋白变化不明显。在未经处理的细胞中，荧光免疫染色显示β-Catenin主要分布在细胞质和/或细胞核中：在TZD处理的细胞中，β-Caten的定位显著转移到质膜，并伴随着该部位E-钙粘附素的增加。因此，PPAR-γ配体似乎不仅参与诱导胰腺癌细胞的生长和分化，而且参与E-钙粘蛋白/β-连环蛋白系统的调节。这种配体可能被证明是临床上有用的细胞抑制抗癌剂。较少

Peroxisome proliferator-activated receptor-γ (PPAR-γ), a transcription factor belonging to the nuclearreceptor superfamily, forms functional heterodimers with the retinoid X receptor. Synthetic PPAR-γ ligands have been shown to inhibit the growth of several human tumor cell lines and to induce growth arrest and differentiation in primary cultures of human liposarcoma, colon cancer, and breast cancer cells in vitro and in vivo. The aim of this study was to examine whether PPAR-γ is expressed at high level in human pancreatic cancer cells, and its ligand can inhibit cellular growth through terminal differentiation of pancreatic cancer cells. In addition, we also examined whether thiazol idinedione (TZD), a potent PPAR-γ ligand. could modulate the E-cadherin/β-catenin system in human pancreatic cancer cells. First, in this study we investigated the expression of PPAR-γ in five pancreatic cancer cell lines: Capan-1(well differentiated adenocarcinema), AsPC-1(moderately differentiated adeno … More carcinoma), BxPC-3(moderately differentiated adenocarcinoma), Panc-1(poorly differentiated adenocarcinoma), and MIAPaCa-2(undifferentiated carcinoma). All five expressed PPAR-γ mRNA and protein, shown respectively on RT-PCR and Western blotting analisis. Clonogenic assaya showed that TZD completely inhibits colony formation of these cells at a concentration of 10 μ M. Moreover, treatment of these cells with 10 μM TZD resulted in GO/G1 cell cyclearrest. According to Western blotting, TZD markedly increased differentiation markers including E-cadherin and CEA, while β-catenin did not change significantly. In untreated cells, fluorescence immunostaining demonstrated β-catenin predominantly in the cytoplasm and/or nucleus: in TZD-treated cells, β-caten in localization had dramatically shifted to the plasma membrane, in association with increased E-cadherin at this site. Thus, a PPAR-γ ligand appears to participate not only in induction of cell growth and differentiation in pancreatic cancer cells, but also in the regulation of E-cadherin/β-catenin system. Such ligands may prove clinically useful as cytostatic anticancer agents. Less