Imprinted DLK1 is a putative tumor suppressor gene and inactivated by epimutation at the region upstream of GTL2 in human renal cell carcinoma
Imprinted DLK1 is a putative tumor suppressor gene and inactivated by epimutation at the region upstream of GTL2 in human renal cell carcinoma
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DOI：
10.1093/hmg/ddl001
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发表时间：
2006-03-15
影响因子：
3.5
通讯作者：
Okamoto, K
中科院分区：
文献类型：
--
作者：
Kawakami, T;Chano, T;Okamoto, K
人肾细胞癌(RCC)染色体臂14q32的常见缺失促使我们探索该区域的肿瘤抑制基因(TSG)。我们报道了脂肪细胞分化调控基因14q32上的印迹DLK1是肾细胞癌中的候选TSG。DLK1在50例原发肾癌组织中有39例表达缺失(78%)，而在所有被检查的正常肾组织中DLK1表达均保持不变。DLK1在15个肾癌来源的细胞系中只有一个(7%)表达。为了了解DLK1失活在肾癌中的生物学意义，我们用含有DLK1基因的重组逆转录病毒检测了DLK1在肾癌细胞系中的修复效果。将DLK1重新导入DLK1缺失的肾癌细胞系可显著增加裸鼠体内锚定非依赖性细胞死亡和失巢凋亡，并抑制肿瘤生长。然后，我们研究了RCC中DLK1失活的潜在机制。我们发现在50例肾癌组织中有12例(24%)该区域存在杂合性缺失。为了探讨DLK1失活的表观遗传调控在肾癌中的作用，我们对DLK1的上游区域和基因体进行了甲基化分析。我们在DLK1的上游区域和基因体中都没有发现差异甲基化区域。然而，我们发现，DLK1的相互印记基因GTL2上游甲基化的获得是RCCS中DLK1失活的关键表观遗传学改变。目前的数据表明，未翻译的GTL2上游甲基化的获得导致RCC中DLK1的病理性下调。
A common deletion at chromosomal arm 14q32 in human renal cell carcinoma (RCC) prompted us to explore a tumor suppressor gene (TSG) in this region. We report that imprinted DLK1 at 14q32, a regulator of adipocyte differentiation, is a candidate TSG in RCCs. DLK1 expression was lost in 39 out of 50 (78%) primary RCC tissues, whereas expression of DLK1 was maintained in every normal kidney tissue examined. DLK1 was expressed in only one of 15 (7%) RCC-derived cell lines. In order to see the biological significance of DLK1 inactivation in RCCs, we tested the effect of restoration of DLK1 in RCC cell lines, using a recombinant retrovirus containing the gene. Reintroduction of DLK1 into DLK1-null RCC cell lines markedly increased anchorage-independent cell death, anoikis and suppressed tumor growth in nude mice. We then investigated the underlying mechanisms for DLK1 inactivation in RCCs. We found loss of heterozygosity at this region in 12 out of 50 RCC tissues (24%). To explore the role of epigenetic regulation of DLK1 inactivation in RCCs, we conducted methylation analysis of the upstream region and the gene body of DLK1. We could not find a differentially methylated region in either the upstream region or the gene body of DLK1. However, we found that gain of methylation upstream of GTL2, a reciprocal imprinted gene for DLK1, is a critical epigenetic alteration for the inactivation of DLK1 in RCCs. The present data have shown that gain of methylation upstream of the untranslated GTL2 leads to pathological downregulation of DLK1 in RCCs.