Oncogenic KRAS activates hedgehog signaling pathway in pancreatic cancer cells
Oncogenic KRAS activates hedgehog signaling pathway in pancreatic cancer cells
复制标题
DOI：
10.1074/jbc.m611089200
复制
发表时间：
2007-05-11
影响因子：
4.8
通讯作者：
Cheng, Xiaodong
中科院分区：
文献类型：
--
作者：
Ji, Zhenyu;Mei, Fang C.;Cheng, Xiaodong
Hedgehog（Hh）信号传导在包括胰腺导管腺癌（PDA）在内的多种人类癌症中失调。由于KRAS突变代表了最早的遗传改变之一，并且几乎普遍发生在PDA中，因此我们假设致癌KRAS部分通过激活Hh通路促进胰腺肿瘤发生。在这里，我们报告，致癌KRAS激活刺猬信号在PDA细胞中，利用下游效应通路介导的RAF/MEK/MAPK，而不是磷脂酰肌醇3-激酶（PI 3 K）/AKT。人胰腺导管上皮细胞的致癌性KRAS转化增加GLI转录活性，该作用被MEK特异性抑制剂U 0126和PD 98059抑制，但不被PI 3 K特异性抑制剂渥曼青霉素抑制。通过对致癌KRAS特异性的小干扰RNA灭活KRAS活性，可抑制具有激活KRAS突变的PDA细胞系中的GLI活性和GLI 1表达; MEK抑制剂U 0126和PD 98059引起类似的反应。此外，BRAFE 600的组成型活性形式而不是myr-AKT的表达阻断了KRAS敲低对Hh信号传导的抑制作用。最后，抑制GLI活性导致突变型KRAS表达PDA细胞的致癌转化活性的选择性减弱。这些结果表明，致癌KRAS，通过RAF/MEK/MAPK信号，是直接参与激活的刺猬途径在PDA细胞和这两个信号通路之间的合作可能在PDA的进展中发挥重要作用。
Hedgehog (Hh) signaling is deregulated in multiple human cancers including pancreatic ductal adenocarcinoma (PDA). Because KRAS mutation represents one of the earliest genetic alterations and occurs almost universally in PDA, we hypothesized that oncogenic KRAS promotes pancreatic tumorigenesis in part through activation of the Hh pathway. Here, we report that oncogenic KRAS activates hedgehog signaling in PDA cells, utilizing a downstream effector pathway mediated by RAF/MEK/MAPK but not phosphatidylinositol 3-kinase (PI3K)/AKT. Oncogenic KRAS transformation of human pancreatic ductal epithelial cells increases GLI transcriptional activity, an effect that is inhibited by the MEK-specific inhibitors U0126 and PD98059, but not by the PI3K-specific inhibitor wortmannin. Inactivation of KRAS activity by a small interfering RNA specific for oncogenic KRAS inhibits GLI activity and GLI1 expression in PDA cell lines with activating KRAS mutation; the MEK inhibitors U0126 and PD98059 elicit a similar response. In addition, expression of the constitutively active form of BRAFE600, but not myr-AKT, blocks the inhibitory effects of KRAS knockdown on Hh signaling. Finally, suppressing GLI activity leads to a selective attenuation of the oncogenic transformation activity of mutant KRAS-expressing PDA cells. These results demonstrate that oncogenic KRAS, through RAF/MEK/MAPK signaling, is directly involved in the activation of the hedgehog pathway in PDA cells and that collaboration between these two signaling pathways may play an important role in PDA progression.