过氧化物酶体增殖物激活受体γ在结肠癌中的表达及其激动剂对结肠癌细胞的生长抑制作用

Expression of peroxisome proliferator-activated receptor γ in human colon cancer and growth inhibition by its agonists

目的探讨过氧化物酶体增殖物激活受体γ(PPARγ)在结肠癌中的表达以及PPARγ激动剂对结肠癌细胞生长的抑制作用、作用途径及可能机制。方法采用SP法检测56例结肠癌及相应正常组织中PPARγ的表达。应用RT-PCR及Western-blot方法检测PPARγ在SW480和LS174T结肠癌细胞中的表达。MTT法检测细胞生长情况,流式细胞仪检测细胞周期和凋亡率。结果结肠癌组织中PPARγ的阳性率为71.4%,显著高于正常组织的44.6%(P<0.01)。PPARγ在Dukes分期C期+D期中的阳性率为82.9%,显著高于A期+B期的52.4%(P<0.05)。PPARγ在有淋巴结或肝转移组的阳性率(分别为81.1%,100%)显著高于无淋巴结或肝转移组的52.6%和66.0%(P值均<0.05)。PPARγ在两种结肠癌细胞中均有表达,其激动剂15脱氧前列腺素J2(15d-PGJ2)和吡格列酮(PGZ)对2种结肠癌细胞均有生长抑制作用,并呈时间和剂量依赖性。PPARγ激动剂的生长抑制作用能部分被其拮抗剂GW9662阻断。15d-PGJ2和PGZ能诱导细胞生长周期改变,即G0/G1期细胞比例增加,而S期明显减少,并诱导凋亡率显著上升(P值均<0.01)。结论PPARγ的高表达与结肠癌的发生、发展有关。15d-PGJ2和PGZ部分通过PPARγ依赖途径抑制结肠癌细胞生长,该作用可能与诱导癌细胞阻滞于G0/G1期及增加细胞凋亡有关。

Objective To investigate the expression of peroxisome proliferator-activated receptor γ （PPARγ） in human colon cancer, as well as the pathway and mechanism of PPARγ agonists inhibiting colon cancer cell growth. Methods The expressions of PPARγ in 56 colon cancer tissues and normal colonic tissues were detected by immunohistochemical methods. The expressions of PPARγ in SW480 and LS174T colon cancer cells were detected by RT-PCR and Western-blot analysis. MTT colorimetric assay was used to detect the inhibition rate. Flow cytometry was used to detect the cell cycle and apoptosis. Resuits PPARγ was over-expressed in colon cancer tissues （71.4%） than in normal colonic tissues （44. 6% ） （ P 〈0.01 ）. Assessed by Dukes stage, the PPARγ expressions in C ＋ D stages （ 82.9% ） were significantly higher than those in A ＋ B stages （ 52.4% ） （ P 〈 0.05 ）. The PPARγ expressions in cases with lymph node or liver metastasis （81. 1% or 100% , respectively） were higher than those without lymph node or liver metastasis （52.6% or 66.0% ,respectively） （P 〈 0.05 ）. Treatment with PPARγ agonists, 15-deoxy- A 12,14 -prostaglandin J2 （15d-PGJ2） or Pioglitazone （ PGZ）, inhibited the growth of SW480 and LS174T ceils in a time- and dose-dependent manner. The growth inhibitory effect of PPARγ agonists could only be partly reversed by PPARγ antagonist GW9662. Flow cytometry was performed. It demonstrated that a large portion of SW480 and LS174T ceils was arrested at G0/G1 phase, and the apoptotic rate of two colon cancer ceils was significantly increased. Conclusions PPARγ can be used as an important pre- dictor involved in carcinogenesis and development of colon carcinoma. 15d-PGJ2 and PGZ may suppress colon cancer ceils partly in PPAR-dependent manner, and this inhibitory effect may be associated with the induction of ceil differentiation and apoptosis.