TGF-β-induced nuclear localization of Smad2 and Smad3 in Smad4 null cancer cell lines
TGF-β-induced nuclear localization of Smad2 and Smad3 in Smad4 null cancer cell lines
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DOI：
10.1038/sj.onc.1206128
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发表时间：
2003-03-06
期刊：
影响因子：
8
通讯作者：
Markowitz, S
中科院分区：
文献类型：
--
作者：
Fink, SP;Mikkola, D;Markowitz, S
Smad 4是一种肿瘤抑制基因，通常在结直肠癌和胰腺癌中丢失或突变。激活的转化生长因子-β（TGF-β）受体使Smad 2和Smad 3磷酸化，然后与Smad 4复合并转运到细胞核。当在一些人类癌症中检测到Smad 4突变时，认为其足以抑制TGF-β信号传导。在这项工作中，我们描述了一种结肠癌细胞系，VACO-9 M，这是Smad 4无效时，通过多种检测分析。为了研究Smad 4在TGF-β诱导的受体激活的Smads易位到细胞核中的作用，我们通过免疫荧光分析了VACO-9 M，加上另外四个乳腺（MDA-MB-468）或胰腺（BxPC 3，Hs 766 T，CFPAC-1）来源的Smad 4无效细胞系的TGF-β处理后内源性Smad 2和Smad 3的细胞定位。在每个细胞系中，TGF-β处理导致Smad 2和Smad 3以Smad 4独立的方式移动到细胞核。然而，Smad 2和Smad 3的核转位不足以激活TGF-β诱导的转录反应的报告者，然而，野生型Smad 4的瞬时转染恢复了转录反应。我们的结论是，Smad 4是不需要的Smad 2和Smad 3的核转位，但需要激活至少某些转录反应。
Smad4 is a tumor suppressor gene that is commonly lost or mutated in colorectal and pancreatic cancers. The activated transforming growth factor-beta (TGF-beta) receptor phosphorylates Smad2 and Smad3, which then complex with Smad4 and translocate to the nucleus. Smad4 mutations when detected as present in some human cancers have been considered sufficient to inactivate TGF-beta signaling. In this work, we describe a colon cancer cell line, VACO-9M, that is Smad4 null when analysed by multiple assays. To study the role of Smad4 in TGF-beta-induced translocation of the receptor-activated Smads to the nucleus, we analysed by immunofluorescence the cellular localization of endogenous Smad2 and Smad3 after TGF-beta treatment of VACO-9M, plus four additional Smad4 null cell lines of breast (MDA-MB-468), or pancreatic (BxPC3, Hs766T, CFPAC-1) origin. In each cell line, TGF-beta treatment resulted in both Smad2 and Smad3 moving to the nucleus in a Smad4-independent fashion. Nuclear translocation of Smad2 and Smad3 was, however, not sufficient to activate reporters for TGF-beta-induced transcriptional responses, which were however restored by transient transfection of wild-type Smad4. We conclude that Smad4 is not required for nuclear translocation of Smad2 and Smad3, but is needed activation of at least certain transcriptional responses.