Wimmel A, Wiedenmann B, Rosewicz S
Medizinische Klinik mit Schwerpunkt Hepatologie, Gastroenterologie, Endokrinologie und Stoffwechsel, CVK, Charité, Augustenburger Platz 1, D-13353, Berlin, Germany.
Gut. 2003 Sep;52(9):1308-16. doi: 10.1136/gut.52.9.1308.
The role of transforming growth factor beta-1 (TGFbeta-1) in neuroendocrine tumour biology is currently unknown. We therefore examined the expression and biological significance of TGFbeta signalling components in neuroendocrine tumours (NETs) of the gastroenteropancreatic (GEP) tract.
Expression of TGFbeta-1 and its receptors, Smads and Smad regulated proteins, was examined in surgically resected NET specimens and human NET cell lines by immunohistochemistry, reverse transcriptase-polymerase chain reaction, immunoblotting, and ELISA. Activation of TGFbeta-1 dependent promoters was tested by transactivation assays. Growth regulation was evaluated by cell numbers, soft agar assays, and cell cycle analysis using flow cytometry. The role of endogenous TGFbeta was assessed by a TGFbeta neutralising antibody and stable transfection of a dominant negative TGFbetaR II receptor construct.
Coexpression of TGFbeta-1 and its receptors TGFbetaR I and TGFbetaR II was detected in 67% of human NETs and in all three NET cell lines examined. NET cell lines expressed the TGFbeta signal transducers Smad 2, 3, and 4. In two of the three cell lines, TGFbeta-1 treatment resulted in transactivation of a TGFbeta responsive reporter construct as well as inhibition of c-myc and induction of p21((WAF1)) expression. TGFbeta-1 inhibited anchorage dependent and independent growth in a time and dose dependent manner in TGFbeta-1 responsive cell lines. TGFbeta-1 mediated growth inhibition was due to G1 arrest without evidence of induction of apoptosis. Functional inactivation of endogenous TGFbeta revealed the existence of an autocrine antiproliferative loop in NET cells.
Neuroendocrine tumour cells of the gastroenteropancreatic tract are subject to paracrine and autocrine growth inhibition by TGFbeta-1, which may account in part for the low proliferative index of this tumour entity.
转化生长因子β-1（TGFβ-1）在神经内分泌肿瘤生物学中的作用目前尚不清楚。因此，我们研究了胃肠胰（GEP）道神经内分泌肿瘤（NETs）中TGFβ信号成分的表达及其生物学意义。
通过免疫组织化学、逆转录-聚合酶链反应、免疫印迹和酶联免疫吸附测定法，检测手术切除的NET标本和人NET细胞系中TGFβ-1及其受体、Smads和Smad调节蛋白的表达。通过反式激活测定法检测TGFβ-1依赖性启动子的激活。使用流式细胞术通过细胞数量、软琼脂测定法和细胞周期分析评估生长调节。通过TGFβ中和抗体和显性负性TGFβR II受体构建体的稳定转染评估内源性TGFβ的作用。
在67%的人NETs和所有检测的三种NET细胞系中检测到TGFβ-1及其受体TGFβR I和TGFβR II的共表达。NET细胞系表达TGFβ信号转导分子Smad 2、3和4。在三种细胞系中的两种中，TGFβ-1处理导致TGFβ反应性报告构建体的反式激活以及c-myc的抑制和p21（WAF1）表达的诱导。TGFβ-1以时间和剂量依赖性方式抑制TGFβ-1反应性细胞系中的贴壁依赖性和非依赖性生长。TGFβ-1介导的生长抑制是由于G1期停滞，没有诱导凋亡的证据。内源性TGFβ的功能失活揭示了NET细胞中自分泌抗增殖环的存在。
胃肠胰道的神经内分泌肿瘤细胞受到TGFβ-1的旁分泌和自分泌生长抑制，这可能部分解释了该肿瘤实体的低增殖指数。
