Reduced Expression of Transforming Growth Factor β Type I Receptor Contributes to the Malignancy of Human Colon Carcinoma Cells*
Reduced Expression of Transforming Growth Factor β Type I Receptor Contributes to the Malignancy of Human Colon Carcinoma Cells*
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DOI：
10.1074/jbc.271.29.17366
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发表时间：
1996-07
期刊：
影响因子：
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通讯作者：
Jing Wang;W. Han;E. Zborowska;Jiurong Liang;Xiaofan Wang;J. Willson;Luzhe Sun;M. Brattain
中科院分区：
文献类型：
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作者：
Jing Wang;W. Han;E. Zborowska;Jiurong Liang;Xiaofan Wang;J. Willson;Luzhe Sun;M. Brattain
转化生长因子β (tgf - β) I型（RI）和II型（RII）受体是tgf - β信号转导所必需的。人类结肠癌细胞系GEO对tgf - β反应微弱，表达的RI mRNA水平较结肠癌细胞低，而结肠癌细胞对tgf - β反应高。因此，我们研究了RI作为TGFβ敏感性的限制因子的作用，以及低RI水平对GEO细胞恶性表型的贡献。稳定转染四环素可调节的大鼠RI cDNA可增加tgf - β1与RI的结合，并导致外源性tgf - β1对RI的生长抑制作用增强。相比之下，虽然将RII表达载体稳定转染到相同的GEO细胞中增加了tgf - β1与RII的结合，但外源tgf - β1对生长的抑制作用并未改变。这表明低水平的RI是tgf - β在GEO细胞中抑制生长作用的限制因素。与GEO对照细胞相比，ri转染细胞在较低的饱和密度下生长受阻。在镀效率和软琼脂糖实验中，它们也显示出生长和克隆原性的降低，而在这些实验中，rii转染的细胞与NEO对照细胞没有任何差异。四环素抑制了转染细胞中RI的表达，逆转了转染RI的克隆的镀效率下降，证实了生长效应是由于转染细胞中RI表达增加所致。tgf - β1中和抗体刺激了RI转染细胞的增殖，但对GEO对照细胞的影响不大，表明自分泌阴性tgf - β活性的增加也与RI表达的增加有关。转染ri的细胞显著延迟了裸小鼠的致瘤性。这些结果表明，低RI表达可能是对外源性TGFβ反应的限制因素，以及TGFβ自分泌负活性，并且RI表达的减少可能有助于恶性进展。
Transforming growth factor β (TGFβ) type I (RI) and type II (RII) receptors are essential for TGFβ signal transduction. A human colon carcinoma cell line, designated GEO, is marginally responsive to TGFβ and expresses a low level of RI mRNA relative to colon carcinoma cells, which are highly responsive to TGFβ. Hence, the role of RI as a limiting factor for TGFβ sensitivity and the contribution of low RI levels to the malignant phenotype of GEO cells were examined. Stable transfection of a tetracycline-regulatable rat RI cDNA increased TGFβ1 binding to RI and resulted in increased growth inhibition by exogenous TGFβ1. In contrast, although stable transfection of an RII expression vector into the same GEO cells increased TGFβ1 binding to RII, growth inhibition by exogenous TGFβ1 was not altered. This indicated that the low level of RI is a limiting factor for the growth-inhibitory effects of TGFβ in GEO cells. RI-transfected cells were growth-arrested at a lower saturation density than GEO control cells. They also showed reduced growth and clonogenicity in plating efficiency and soft agarose assays, whereas RII-transfected cells did not show any differences from the NEO control cells in these assays. Tetracycline repressed RI expression in transfected cells and reversed the reduction in plating efficiency of RI-transfected clones, confirming that growth effects were due to increased RI expression in transfected cells. TGFβ1 neutralizing antibody stimulated the proliferation of RI-transfected cells but had little effect on GEO control cells, indicating that increased autocrine-negative TGFβ activity also resulted from increased RI expression. Tumorigenicity in athymic nude mice was significantly delayed in RI-transfected cells. These results indicate that low RI expression can be a limiting factor for response to exogenous TGFβ, as well as TGFβ autocrine-negative activity, and that reduction of RI expression can contribute to malignant progression.