Overexpression of human Dickkopf-1, an antagonist of wingless/WNT signaling, in human hepatoblastomas and Wilms' tumors
Overexpression of human Dickkopf-1, an antagonist of wingless/WNT signaling, in human hepatoblastomas and Wilms' tumors
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DOI：
10.1097/01.lab.0000059926.66359.bd
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发表时间：
2003-03-01
影响因子：
5
通讯作者：
Pietsch, T
中科院分区：
文献类型：
--
作者：
Wirths, O;Waha, A;Pietsch, T
肝母细胞瘤（HB）是儿童最常见的恶性肝脏肿瘤，但对这些肿瘤的分子发病机制和表达模式的改变知之甚少。我们使用抑制性消减杂交方法来鉴定可能在HB肿瘤发生中起作用的新的候选基因。从HB cDNA中减去来自相应肝脏和胎肝的cDNA种类，并分离出一系列差异表达的感兴趣的候选物。在HB中过表达的转录本之一来自人类Dickkopf-1（hDkk-1）基因，该基因编码一种分泌蛋白，作为无翅/WNT信号通路的有效抑制剂。我们使用差异PCR方法和北方印迹法检测了32例HB活检标本和相应的肝脏样本、4个HB细胞系以及一组其他肿瘤和正常组织中的hDkk-1表达水平。81%的HB，但没有一个正常的儿科或胎儿肝组织显示hDkk-1表达。hDkk-1转录本也存在于6个肾母细胞瘤中的5个中，但仅在20个肝细胞癌样品中的2个和5个髓母细胞瘤细胞系中的1个中微弱地检测到;转录本在恶性胶质瘤和乳腺癌中不存在。WNT发育控制途径中的中心效应分子是β-连环蛋白。有趣的是，先前已经在48%的HB中鉴定出β-连环蛋白基因的激活突变，并且超过85%的HB显示β-连环蛋白蛋白的积累作为激活途径的指示物。因此，抑制剂Dkk-1的过表达可能与不受控制的无翅/WNT信号传导有关，并且可能代表负反馈机制。hDkk-1表达代表了HB和Wilms肿瘤的新标志物。
Hepatoblastomas (HBs) represent the most frequent malignant liver tumors of childhood; yet little is known about the molecular pathogenesis and the alterations in expression patterns of these tumors. We used a suppression subtractive hybridization approach to identify new candidate genes that may play a role in HB tumorigenesis. cDNA species derived from corresponding liver and fetal liver were subtracted from HB cDNAs, and a series of interesting candidates were isolated that were differentially expressed. One of the transcripts overexpressed in HB was derived from the human Dickkopf-1 (hDkk-1) gene, which encodes a secreted protein acting as a potent inhibitor of the wingless/WNT signaling pathway. We examined the hDkk-1 expression levels in 32 HB biopsy specimens and in the corresponding liver samples, in 4 HB cell lines, and in a panel of other tumors and normal tissues using a differential PCR approach and Northern blotting. Eighty-one percent of the HBs but none of the normal pediatric or fetal liver tissues showed hDkk-1 expression. hDkk-1 transcripts were also present in 5 of 6 Wilms'tumors but only weakly detectable in 2 of 20 hepatocellular carcinoma samples and in 1 of 5 medulloblastoma cell lines; transcripts were absent in malignant gliomas and breast cancer. The central effector molecule in the WNT developmental control pathway is the beta-catenin protein. Interestingly, activating mutations of the beta-catenin gene have previously been identified in 48% of HBs, and more than 85% of HBs show accumulation of beta-catenin protein as the indicator for an activated pathway. The overexpression of the inhibitor Dkk-1 may therefore be related to uncontrolled wingless/WNT signaling and may represent a negative feedback mechanism. hDkk-1 expression represents a novel marker for HBs and Wilms' tumors.