Kruppel-like factor 5 mediates the transforming activity of oncogenic H-Ras
Kruppel-like factor 5 mediates the transforming activity of oncogenic H-Ras
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DOI：
10.1038/sj.onc.1207397
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发表时间：
2004-04-22
期刊：
影响因子：
8
通讯作者：
Yang, VW
中科院分区：
文献类型：
--
作者：
Nandan, MO;Yoon, HS;Yang, VW
以前的研究表明，Kruppel样因子5（KLF 5），也称为富含丝氨酸的Kruppel样因子（IKLF），是细胞增殖的正调节因子，当过表达时会产生转化表型。在这里，我们证明，KLF 5的转录和蛋白质的水平显着升高，在致癌H-Ras转化的NIH 3 T3细胞。这些细胞在含血清和无血清培养基中均显示出加速的增殖速率，并在软琼脂测定中形成非贴壁依赖性集落。H-Ras转化的细胞还含有升高的促分裂原活化蛋白激酶（MAPK）活性。当用MEK（MAPK激酶）抑制剂处理时，H-Ras转化的细胞失去其生长优势并且不再形成集落。值得注意的是，在用MEK抑制剂处理的H-Ras转化细胞中，KLF 5转录物和蛋白质的水平显著降低。此外，在H-Ras转化细胞中用KLF 5特异性小干扰RNA（siRNA）抑制KLF 5表达导致增殖速率降低和集落形成显著减少。H-Ras转化的细胞还含有升高水平的Egr 1，其被MEK抑制剂减少。通过siRNA抑制Egr 1导致KLF 5水平降低，表明Egr 1介导MAPK对KLF 5的诱导作用。最后，KLF 5激活细胞周期蛋白D1的表达。这些发现表明，在H-Ras转化细胞中KLF 5表达的增加是继发于H-Ras过表达引起的MAPK活性增加，并且KLF 5水平升高部分地负责致癌H-Ras的促增殖和转化活性。
Previous studies indicate that Kruppel-like factor 5 (KLF5), also known as intestinal-enriched Kruppel-like factor (IKLF), is a positive regulator of cell proliferation and gives rise to a transformed phenotype when overexpressed. Here we demonstrate that levels of KLF5 transcript and protein are significantly elevated in oncogenic H-Ras-transformed NIH3T3 cells. These cells display an accelerated rate of proliferation in both serum-containing and serum-deprived media and form anchorage-independent colonies in soft agar assays. H-Ras-transformed cells also contain elevated mitogen-activated protein kinase (MAPK) activity. When treated with inhibitors of MEK ( MAPK kinase), H-Ras-transformed cells lose their growth advantage and no longer form colonies. Significantly, levels of KLF5 transcript and protein are substantially reduced in H-Ras-transformed cells treated with MEK inhibitors. Moreover, inhibition of KLF5 expression in H-Ras-transformed cells with KLF5-specific small interfering RNA ( siRNA) leads to a decreased rate of proliferation and a significant reduction in colony formation. H-Ras-transformed cells also contain elevated levels of Egr1 that are diminished by MEK inhibitors. Inhibition of Egr1 by siRNA results in a reduced level of KLF5, indicating that Egr1 mediates the inductive action of MAPK on KLF5. Lastly, KLF5 activates expression of cyclin D1. These findings indicate that the increased expression of KLF5 in H-Ras-transformed cells is secondary to increased MAPK activity from H-Ras overexpression and that the elevated level of KLF5 is in part responsible for the proproliferative and transforming activities of oncogenic H-Ras.