Park Jae-Il, Lee Min-Goo, Cho Kyucheol, Park Bum-Joon, Chae Kwon-Seok, Byun Do-Sun, Ryu Byung-Kyu, Park Yong-Keun, Chi Sung-Gil
Department of Pathology, College of Medicine, Kyung Hee University, Seoul, 130-701, Republic of Korea.
Oncogene. 2003 Jul 10;22(28):4314-32. doi: 10.1038/sj.onc.1206478.
Transforming growth factor (TGF)-beta1 acts as a potent growth inhibitor of prostate epithelial cells, and aberrant function of its receptor type I and II correlates with tumor aggressiveness. However, intracellular and serum TGF-beta1 levels are elevated in prostate cancer patients and further increased in patients with metastatic carcinoma, suggesting the oncogenic switch of TGF-beta1 role in prostate tumorigenesis. Recently, we reported the mitogenic conversion of TGF-beta1 effect by oncogenic Ha-Ras in prostate cancer cells. Here, we show that TGF-beta1 activates interleukin (IL)-6, which has been implicated in the malignant progression of prostate cancers, via multiple signaling pathways including Smad2, nuclear factor-kappaB (NF-kappaB), JNK, and Ras. TGF-beta1-induced IL-6 gene expression was strongly inhibited by DN-Smad2 but not by DN-Smad3 while it was further activated by wild-type Smad2 transfection. IL-6 activation by TGF-beta1 was accompanied by nuclear translocation of NF-kappaB, which was blocked by the p38 inhibitors SB202190 and SB203580 or by IkappaBalphaDeltaN transfection, indicating the crucial role for the p38-NF-kappaB signaling in TGF-beta1 induction of IL-6. TGF-beta1 activated c-Jun phosphorylation, and IL-6 induction by TGF-beta1 was severely impeded by DN-c-Jun and DN-JNK or AP-1 inhibitor curcumin, showing that the JNK-c-Jun-AP-1 signaling plays a pivotal role in TGF-beta1 stimulation of IL-6. It was also found that the Ras-Raf-MEK1 cascade is activated by TGF-beta1 and participates in the TGF-beta1 induction of IL-6 in an AP-1-dependent manner. Cotransfection assays demonstrated that TGF-beta1 stimulation of IL-6 results from the synergistic collaboration of the Smad2, p38-NF-kappaB, JNK-c-Jun-AP-1, or Ras-Raf-MEK1 cascades. In addition, a time course IL-6 decay revealed that mRNA stability of IL-6 is modestly increased by TGF-beta1, indicating that TGF-beta1 also regulates IL-6 at the post-transcriptional level. Intriguingly, IL-6 inactivation restored the sensitivity to TGF-beta1-mediated growth arrest and apoptosis, suggesting that elevated IL-6 in advanced prostate tumors might act as a resistance factor against TGF-beta1. Collectively, our data demonstrate that IL-6 expression is stimulated by tumor-producing TGF-beta1 in human prostate cancer cells through multiple signaling pathways including Smad2, p38, JNK, and Ras, and enhanced expression of IL-6 could contribute to the oncogenic switch of TGF-beta1 role for prostate tumorigenesis, in part by counteracting its growth suppression function.
转化生长因子（TGF）-β1作为前列腺上皮细胞的一种强效生长抑制剂，其I型和II型受体的异常功能与肿瘤侵袭性相关。然而，前列腺癌患者的细胞内和血清TGF-β1水平升高，转移性癌患者的该水平进一步升高，这表明TGF-β1在前列腺肿瘤发生中的作用发生了致癌性转变。最近，我们报道了致癌性Ha-Ras在前列腺癌细胞中使TGF-β1的作用发生有丝分裂原性转变。在此，我们表明TGF-β1通过包括Smad2、核因子-κB（NF-κB）、JNK和Ras在内的多种信号通路激活白细胞介素（IL）-6，IL-6与前列腺癌的恶性进展有关。TGF-β1诱导的IL-6基因表达被显性负性Smad2强烈抑制，但不被显性负性Smad3抑制，而野生型Smad2转染可进一步激活该表达。TGF-β1对IL-6的激活伴随着NF-κB的核转位，p38抑制剂SB202190和SB203580或IkappaBalphaDeltaN转染可阻断这种核转位，这表明p38-NF-κB信号在TGF-β1诱导IL-6中起关键作用。TGF-β1激活c-Jun磷酸化，显性负性c-Jun和显性负性JNK或AP-1抑制剂姜黄素严重阻碍TGF-β1诱导的IL-6，表明JNK-c-Jun-AP-1信号在TGF-β1刺激IL-6中起关键作用。还发现Ras-Raf-MEK1级联被TGF-β1激活，并以AP-1依赖的方式参与TGF-β1诱导IL-6。共转染实验表明，TGF-β1对IL-6的刺激是由Smad2、p38-NF-κB、JNK-c-Jun-AP-1或Ras-Raf-MEK1级联的协同作用所致。此外，IL-6衰减的时间进程显示，TGF-β1适度增加了IL-6的mRNA稳定性，这表明TGF-β1也在转录后水平调节IL-6。有趣的是，IL-6失活恢复了对TGF-β1介导的生长停滞和凋亡的敏感性，这表明晚期前列腺肿瘤中升高的IL-6可能作为一种针对TGF-β1的抗性因子。总的来说，我们的数据表明，肿瘤产生的TGF-β1通过包括Smad2、p38、JNK和Ras在内的多种信号通路刺激人前列腺癌细胞中IL-6的表达，IL-6表达的增强可能部分通过抵消其生长抑制功能，有助于TGF-β1在前列腺肿瘤发生中的致癌性转变。
