Matsuzaki K, Date M, Furukawa F, Tahashi Y, Matsushita M, Sakitani K, Yamashiki N, Seki T, Saito H, Nishizawa M, Fujisawa J, Inoue K
Third Department of Internal Medicine, Kansai Medical University, Osaka, Japan.
Cancer Res. 2000 Mar 1;60(5):1394-402.
The serum concentration of transforming growth factor beta (TGF-beta) is elevated as tumors progress in hepatocellular carcinoma (HCC) patients. In this study, we examined whether modulation of tumor-derived TGF-beta signal transduction contributes to malignant progression. We investigated the production of TGF-beta1, the biological effects of TGF-beta and neutralizing antibody on HCC cells, activation of Smad 2, Smad 3, and Smad 4, induction of antagonistic Smads (Smad 6 and Smad 7), and promoter activities of two target genes, plasminogen activator inhibitor type 1 (PAI-1) and p15INK4B. In human cell lines HCC-M and HCC-T, TGF-beta accelerates their proliferation. Smad 2 was activated constitutively by an autocrine mechanism, because in the absence of exogenous TGF-beta, a high level of Smad 2 phosphorylation, induction of PAI-1 transcripts, and nuclear localization of Smad 2 were observed. This constitutive activation of Smad 2 was, at least in part, attributable to the lack of induction of antagonistic Smads by TGF-beta. However, Smads activated by tumor-derived TGF-beta constantly suppressed p151NK4B expression. In addition, 3 of 10 human HCC tissues showed nuclear localization of Smad 2 and low mRNA levels of p15INK4B and antagonistic Smads but a high level of PAI-1. Our observations suggest that this constant suppression of the p15INK4B gene could be involved in the malignant progression of HCC.
在肝细胞癌（HCC）患者中，随着肿瘤进展，转化生长因子β（TGF-β）的血清浓度会升高。在本研究中，我们检测了肿瘤来源的TGF-β信号转导调节是否促进恶性进展。我们研究了TGF-β1的产生、TGF-β和中和抗体对HCC细胞的生物学效应、Smad 2、Smad 3和Smad 4的激活、拮抗Smads（Smad 6和Smad 7）的诱导以及两个靶基因纤溶酶原激活物抑制剂1型（PAI-1）和p15INK4B的启动子活性。在人细胞系HCC-M和HCC-T中，TGF-β加速它们的增殖。Smad 2通过自分泌机制被组成性激活，因为在没有外源性TGF-β的情况下，观察到高水平的Smad 2磷酸化、PAI-1转录本的诱导以及Smad 2的核定位。Smad 2的这种组成性激活至少部分归因于TGF-β未诱导拮抗Smads。然而，由肿瘤来源的TGF-β激活的Smads持续抑制p151NK4B表达。此外，10例人HCC组织中有3例显示Smad 2的核定位以及p15INK4B和拮抗Smads的低mRNA水平，但PAI-1水平较高。我们的观察结果表明，p15INK4B基因的这种持续抑制可能参与了HCC的恶性进展。
