Transforming growth factor-β-mediated p15INK4B induction and growth inhibition in astrocytes is SMAD3-dependent and a pathway prominently altered in human glioma cell lines
Transforming growth factor-β-mediated p15INK4B induction and growth inhibition in astrocytes is SMAD3-dependent and a pathway prominently altered in human glioma cell lines
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DOI：
10.1074/jbc.274.49.35053
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发表时间：
1999-12-03
影响因子：
4.8
通讯作者：
Wang, XF
中科院分区：
文献类型：
--
作者：
Rich, JN;Zhang, M;Wang, XF
我们试图描述多功能细胞因子转化生长因子-β(TGF-β)抑制正常星形胶质细胞增殖的途径，并分析了人脑胶质瘤细胞系中转化生长因子-β途径的变化。经转化生长因子-β处理后，原代大鼠星形胶质细胞胸腺嘧啶核苷掺入后DNA合成显著减少，细胞周期停滞于G(1)期。对星形胶质细胞的Western分析显示，经转化生长因子-β处理后，细胞周期蛋白依赖性激酶抑制物(CDKI)p15(INK4B)的表达显著上调，而其他CDKI水平没有改变。视网膜母细胞瘤蛋白(Rb)发生低磷酸化，CDK2活性降低。对Smad3基因缺失的小鼠星形胶质细胞的分析表明，与野生型小鼠星形胶质细胞相比，转化生长因子-β介导的生长抑制和p15(INK4B)的诱导都显著丧失。Smad3和Smad4腺病毒感染大鼠星形胶质细胞不能诱导p15(INK4B)的表达增加，提示Smad3对p15(INK4B)的转录有间接调控作用。高级别人脑胶质瘤分泌转化生长因子-β，但对其生长抑制作用具有抵抗力。对12个人脑胶质瘤细胞系的作用分析表明，转化生长因子-β对6个细胞系有轻度抑制作用，对4个细胞系无影响，对2个细胞系有促进作用。除了两株表达p15(INK4B)蛋白的胶质瘤细胞系外，大多数胶质瘤细胞系都存在p15(INK4B)基因的纯合缺失，经转化生长因子-β处理后，p15(INK4B)蛋白被进一步诱导。3株细胞对转化生长因子-β有轻度诱导CDKI p21(WAF1)表达的作用。大多数肿瘤细胞系保留了其他转化生长因子-β介导的反应，包括细胞外基质蛋白和血管生成因子分泌，这可能有助于增加恶性行为。这表明，p15(INK4B)的丢失可能部分解释了胶质瘤中转化生长因子-β选择性丧失生长抑制以形成更具侵袭性的肿瘤表型。
We sought to characterize the pathway by which the multifunctional cytokine transforming growth factor-beta (TGF-beta) inhibits the proliferation of normal astrocytes, and we analyzed the alterations in the TGF-beta pathway in human glioma cell lines. Upon TGF-beta treatment, primary rat astrocytes showed a significant decrease in DNA synthesis upon thymidine incorporation with a cell cycle arrest in the G(1) phase. Western analysis of the astrocytes revealed that the expression of the cyclin-dependent kinase inhibitor (CdkI) p15(INK4B) was significantly up-regulated upon TGF-beta treatment without a change in other CdkI levels. The retinoblastoma protein (Rb) became hypophosphorylated, and Cdk2 activity decreased. Analysis of Smad3 null mouse astrocytes showed a significant loss of both TGF-beta-mediated growth inhibition and p15(INK4B) induction compared with wild-type mouse astrocytes. Infection of rat astrocytes by SMAD3 and SMAD4 adenoviruses failed to induce increased expression of p15(INK4B), implying indirect transcriptional regulation of p15(INK4B) by SMAD3, High-grade human gliomas secrete TGF-beta, yet are resistant to its growth inhibitory effects. Analysis of the effects of TGF-beta on 12 human glioma cell lines showed that TGF-beta mildly inhibited the growth of six lines, had no effect on four lines, and stimulated the growth of two lines. The majority of glioma lines had homozygous deletions of the p15(INK4B) gene, except for two lines that expressed p15(INK4B) protein, which was induced further upon TGF-beta treatment. Three lines mildly induced CdkI p21(WAF1) expression in response to TGF-beta. Most tumor lines retained other TGF-beta-mediated responses, including extracellular matrix protein and angiogenic factor secretion, which may contribute to increased malignant behavior. This suggests that the loss of p15(INK4B) may explain, in part, the selective loss of growth inhibition by TGF-beta in gliomas to form a more aggressive tumor phenotype.