Identification of novel VHL target genes and relationship to hypoxic response pathways
Oncogene advance online publication 11 April 2005;
Upregulation of hypoxia-inducible factors HIF-1 and HIF-2 is frequent in human cancers and may result from tissue hypoxia or genetic mechanisms, in particular the inactivation of the von Hippel-Lindau (VHL) tumour suppressor gene (TSG). Tumours with VHL inactivation are highly vascular, but it is unclear to what extent HIF-dependent and HIF-independent mechanisms account for pVHL tumour suppressor activity. As the identification of novel pVHL targets might provide insights into pVHL tumour suppressor activity, we performed gene expression microarray analysis in VHL-wild-type and VHL-null renal cell carcinoma (RCC) cell lines. We identified 30 differentially regulated pVHL targets (26 of which were 'novel') and the results of microarray analysis were confirmed in all 11 novel targets further analysed by real-time RT-PCR or Western blotting. Furthermore, nine of 11 targets were dysregulated in the majority of a series of primary clear cell RCC with VHL inactivation. Three of the nine targets had been identified previously as candidate TSGs (DOC-2/DAB2, CDKN1C and SPARC) and all were upregulated by wild-type pVHL. The significance for pVHL function of two further genes upregulated by wild-type pVHL was initially unclear, but re-expression of GNG4 (G protein gamma-4 subunit/guanine nucleotide-binding protein-4) and MLC2 (myosin light chain) in a RCC cell line suppressed tumour cell growth. pVHL regulation of CDKN1C, SPARC and GNG4 was not mimicked by hypoxia, whereas for six of 11 novel targets analysed (including DOC-2/DAB2 and MLC2) the effects of pVHL inactivation and hypoxia were similar. For GPR56 there was evidence of a tissue-specific hypoxia response. Such a phenomenon might, in part, explain organ-specific tumorigenesis in VHL disease. These provide insights into mechanisms of pVHL tumour suppressor function and identify novel hypoxia-responsive targets that might be implicated in tumorigenesis in both VHL disease and in other cancers with HIF upregulation.
缺氧可诱导因子HIF-1和HIF-2 的向上调节在人类癌中经常发生，并且可能是由于组织缺氧或基因的机制造成，尤其可能是由于 von Hippel-Lindau (VHL)肿瘤抑制基因(TSG)的钝化造成的。VHL钝化的瘤具有高度血管化，但它多大程度地依赖于或不依赖于HIF机制对pVHL肿瘤抑制活性的影响还不清楚。随着新型pVHL目的基因的确认，可能会使我们对pVHL肿瘤抑制活性有更深入的了解，我们对VHL野生型和无VHL的肾细胞瘤 (RCC) 细胞系进行基因表达微阵列分析，确认了30个不同的pVHL目的调节基因（其中20个是新发现的），并且这些微阵列分析结果在利用实时RT-PCR或西部印迹法对11个新型基因的进一步分析中得到证明。进一步证明了11个基因的9个在VHL钝化的大部分原生透明细胞RCC中是失调的。9个目的基因的三个先前已被确认为候补TSGs(DOC-2/DAB2, CDKN1C and SPARC)，并且这9个基因都被野生pVHL上调节。这些被向上调节的基因的作用最初不很清楚，但在RCC细胞系中GNG4 (G 蛋白γ-4亚基/鸟苷结合蛋白-4) 和MLC2 (肌球蛋白轻链) 的重新表达抑制了肿瘤细胞的生长。CDKN1C, SPARC 和GNG4的pVHL调节不能在组织缺氧下模拟出来，而对11个新型基因中的6个基因分析（包括DOC-2/DAB2 和MLC2）其与pVHL钝化和组织缺氧的效果却是相似的。对GPR56有组织特异性缺氧反应的证据。这些现象可能部分的解释了VHL疾病中器官特异性肿瘤的生成。这使我们对pVHL肿瘤抑制功能有了新的认识，并且确认新型的缺氧反应性目的基因可能与VHL疾病及其它HIF上调节的癌的肿瘤生长有关。 [标签:content1][标签:content2]
作者:admin@医学,生命科学 2011-04-07 18:13