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目的:探讨配体活化的过氧化物酶体增殖物激活受体γ(PPARγ)抑制结肠癌细胞生长,及诱导细胞凋亡的作用。方法:逆转录-聚合酶链反应(RT-PCR)及免疫杂交(Western-blot)法测定PPARγ在SW480和LS174T结肠癌细胞中的表达。MTT法检测PPARγ激动剂15脱氧前列腺素J2(15d-PGJ2)和吡格列酮(Pioglita-zone,PGZ)对结肠癌细胞生长的抑制作用。流式细胞术检测细胞凋亡率,电镜观察凋亡细胞形态。免疫细胞化学法检测凋亡相关分子Fas、bcl-XL蛋白表达的变化。结果:PPARγ在SW480和LS174T结肠癌细胞株中均有表达,15d-PGJ2和PGZ对两种细胞的生长均有抑制作用,并呈剂量依赖效应。15d-PGJ2和PGZ显著诱导结肠癌细胞凋亡率增加(P<0.05或P<0.01),电镜显示凋亡细胞特有的形态学改变。免疫细胞化学结果显示,PPARγ激动剂诱导Fas蛋白表达明显增多(P<0.01),bcl-XL蛋白表达显著降低(P<0.01),该改变与凋亡程度呈正相关。结论:PPARγ经配体活化后,通过诱导凋亡抑制结肠癌细胞增殖,该作用可能与促凋亡基因Fas抗原表达上调以及凋亡抑制基因bcl-XL表达下调相关。
Objective: To investigate the effect of ligand-activated peroxisome proliferator-activated receptor γ (PPARγ) on the growth of colon cancer cells and the induction of apoptosis. Methods: The expression of PPARγ in SW480 and LS174T colon cancer cells was determined by reverse transcription-polymerase chain reaction (RT-PCR) and immunoblotting (Western-blot). MTT assay was used to detect the inhibitory effect of PPARγ agonist 15 deoxy-prostaglandin J2 (15d-PGJ2) and pioglitazone (PGZ) on the growth of colon cancer cells. The apoptosis rate was detected by flow cytometry and the morphology of apoptotic cells was observed by electron microscope. Immunocytochemistry was used to detect the expression of Fas and bcl-XL protein. Results: PPARγ was expressed in both SW480 and LS174T colon cancer cell lines. Both 15d-PGJ2 and PGZ inhibited the growth of both cell lines in a dose-dependent manner. 15d-PGJ2 and PGZ significantly increased the apoptosis rate of colon cancer cells (P <0.05 or P <0.01), and electron microscopy showed the morphological changes of apoptotic cells. Immunocytochemistry showed that the expression of Fas protein was significantly increased (P <0.01), and the expression of bcl-XL protein was significantly decreased (P <0.01). The change was positively correlated with the degree of apoptosis. Conclusion: Activation of PPARγ can inhibit the proliferation of colon cancer cells by inducing apoptosis, which may be related to the up-regulation of Fas antigen and the down-regulation of apoptosis-inhibiting gene bcl-XL.