Gotzmann J, Fischer A N M, Zojer M, Mikula M, Proell V, Huber H, Jechlinger M, Waerner T, Weith A, Beug H, Mikulits W
Department of Medicine I, Division: Institute of Cancer Research, Medical University of Vienna, Vienna, Austria.
Oncogene. 2006 May 25;25(22):3170-85. doi: 10.1038/sj.onc.1209083.
Polarized hepatocytes expressing hyperactive Ha-Ras adopt an invasive and metastatic phenotype in cooperation with transforming growth factor (TGF)-beta. This dramatic increase in malignancy is displayed by an epithelial to mesenchymal transition (EMT), which mimics the TGF-beta-mediated progression of human hepatocellular carcinomas. In culture, hepatocellular EMT occurs highly synchronously, facilitating the analysis of molecular events underlying the various stages of this process. Here, we show that in response to TGF-beta, phosphorylated Smads rapidly translocated into the nucleus and activated transcription of target genes such as E-cadherin repressors of the Snail superfamily, causing loss of cell adhesion. Within the TGF-beta superfamily of cytokines, TGF-beta1, -beta2 and -beta3 were specific for the induction of hepatocellular EMT. Expression profiling of EMT kinetics revealed 78 up- and 235 downregulated genes, which preferentially modulate metabolic activities, extracellular matrix composition, transcriptional activities and cell survival. Independent of the genetic background, platelet-derived growth factor (PDGF)-A ligand and both PDGF receptor subunits were highly elevated, together with autocrine secretion of bioactive PDGF. Interference with PDGF signalling by employing hepatocytes expressing the dominant-negative PDGF-alpha receptor revealed decreased TGF-beta-induced migration in vitro and efficient suppression of tumour growth in vivo. In conclusion, these results provide evidence for a crucial role of PDGF in TGF-beta-mediated tumour progression of hepatocytes and suggest PDGF as a target for therapeutic intervention in liver cancer.
表达高活性Ha-Ras的极化肝细胞与转化生长因子（TGF）-β协同作用，呈现侵袭性和转移性表型。这种恶性程度的显著增加表现为上皮-间质转化（EMT），它模拟了TGF-β介导的人类肝细胞癌进展。在培养中，肝细胞EMT高度同步发生，便于分析这一过程各个阶段的分子事件。在这里，我们表明，响应TGF-β时，磷酸化的Smads迅速转运到细胞核中，并激活诸如Snail超家族的E-钙粘蛋白抑制因子等靶基因的转录，导致细胞粘附丧失。在细胞因子的TGF-β超家族中，TGF-β1、-β2和-β3对肝细胞EMT的诱导具有特异性。EMT动力学的表达谱分析揭示了78个上调和235个下调基因，这些基因优先调节代谢活动、细胞外基质组成、转录活性和细胞存活。与遗传背景无关，血小板衍生生长因子（PDGF）-A配体和两个PDGF受体亚基均高度升高，同时生物活性PDGF自分泌。通过使用表达显性负性PDGF-α受体的肝细胞干扰PDGF信号传导，显示体外TGF-β诱导的迁移减少，体内肿瘤生长得到有效抑制。总之，这些结果为PDGF在TGF-β介导的肝细胞肿瘤进展中的关键作用提供了证据，并表明PDGF作为肝癌治疗干预的靶点。
