Boerboom Derek, White Lisa D, Dalle Sophie, Courty José, Richards Joanne S
Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Cancer Res. 2006 Feb 15;66(4):1964-73. doi: 10.1158/0008-5472.CAN-05-3493.
Wnt/beta-catenin signaling is normally involved in embryonic development and tissue homeostasis, and its misregulation leads to several forms of cancer. We have reported that misregulated Wnt/beta-catenin signaling occurs in ovarian granulosa cell tumors (GCT) and have created the Catnb(flox(ex3)/+);Amhr2(cre/+) mouse model, which expresses a dominant-stable mutant of beta-catenin in granulosa cells and develops late-onset GCT. To study the mechanisms leading to GCT development, gene expression analysis was done using microarrays comparing Catnb(flox(ex3)/+);Amhr2(cre/+) ovaries bearing pretumoral lesions with control ovaries. Overexpressed genes identified in Catnb(flox(ex3)/+);Amhr2(cre/+) ovaries included the Wnt/beta-catenin signaling antagonists Wif1, Nkd1, Dkk4, and Axin2, consistent with the induction of negative feedback loops that counteract uncontrolled Wnt/beta-catenin signaling. Expression of the antagonists was localized to cells forming the pretumoral lesions but not to normal granulosa cells. Microarray analyses also revealed the ectopic expression of bone markers, including Ibsp, Cdkn1c, Bmp4, and Tnfrsf11b, as well as neuronal/neurosecretory cell markers, such as Cck, Amph, Pitx1, and Sp5. Increased expression of the gene encoding the cytokine pleiotrophin was also found in Catnb(flox(ex3)/+);Amhr2(cre/+) ovaries and GCT but was not associated with increased serum pleiotrophin levels. In situ hybridization analyses using GCT from Catnb(flox(ex3)/+);Amhr2(cre/+) mice revealed that Wnt/beta-catenin antagonists and neuronal markers localized to a particular cell population, whereas the bone markers localized to a distinct cell type associated with areas of osseous metaplasia. Together, these results suggest that misregulated Wnt/beta-catenin signaling alters the fate of granulosa cells and that the GCT that arise in Catnb(flox(ex3)/+);Amhr2(cre/+) mice result from the clonal expansion of metaplastic cells.
Wnt/β-连环蛋白信号通路通常参与胚胎发育和组织稳态，其调控异常会导致多种癌症。我们曾报道，Wnt/β-连环蛋白信号通路调控异常发生在卵巢颗粒细胞瘤（GCT）中，并构建了Catnb(flox(ex3)/+);Amhr2(cre/+)小鼠模型，该模型在颗粒细胞中表达一种显性稳定的β-连环蛋白突变体，并发生迟发性GCT。为研究导致GCT发生的机制，使用微阵列对带有肿瘤前病变的Catnb(flox(ex3)/+);Amhr2(cre/+)卵巢与对照卵巢进行基因表达分析。在Catnb(flox(ex3)/+);Amhr2(cre/+)卵巢中鉴定出的过表达基因包括Wnt/β-连环蛋白信号拮抗剂Wif1、Nkd1、Dkk4和Axin2，这与诱导负反馈环以抵消不受控制的Wnt/β-连环蛋白信号一致。拮抗剂的表达定位于形成肿瘤前病变的细胞，而非正常颗粒细胞。微阵列分析还揭示了骨标志物的异位表达，包括Ibsp、Cdkn1c、Bmp4和Tnfrsf11b，以及神经元/神经分泌细胞标志物，如Cck、Amph、Pitx1和Sp5。在Catnb(flox(ex3)/+);Amhr2(cre/+)卵巢和GCT中也发现编码细胞因子多效生长因子的基因表达增加，但与血清多效生长因子水平升高无关。使用来自Catnb(flox(ex3)/+);Amhr2(cre/+)小鼠的GCT进行原位杂交分析表明，Wnt/β-连环蛋白拮抗剂和神经元标志物定位于特定细胞群，而骨标志物定位于与骨化生区域相关的不同细胞类型。总之，这些结果表明，Wnt/β-连环蛋白信号通路调控异常改变了颗粒细胞的命运，并且Catnb(flox(ex3)/+);Amhr2(cre/+)小鼠中出现的GCT是化生细胞克隆扩增的结果。
