Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
Oncogene. 2012 Mar 22;31(12):1504-20. doi: 10.1038/onc.2011.341. Epub 2011 Aug 22.
WNT, RAS or phosphoinositide 3-kinase signaling pathways control specific stages of ovarian follicular development. To analyze the functional interactions of these pathways in granulosa cells during follicular development in vivo, we generated specific mutant mouse models. Stable activation of the WNT signaling effector β-catenin (CTNNB1) in granulosa cells results in the formation of premalignant lesions that develop into granulosa cell tumors (GCTs) spontaneously later in life or following targeted deletion of the tumor suppressor gene Pten. Conversely, expression of oncogenic KRAS(G12D) dramatically arrests proliferation, differentiation and apoptosis in granulosa cells, and consequently, small abnormal follicle-like structures devoid of oocytes accumulate in the ovary. Because of the potent anti-proliferative effects of KRAS(G12D) in granulosa cells, we sought to determine whether KRAS(G12D) would block precancerous lesion and tumor formation in follicles of the CTNNB1-mutant mice. Unexpectedly, transgenic Ctnnb1;Kras-mutant mice exhibited increased GC proliferation, decreased apoptosis and impaired differentiation and developed early-onset GCTs leading to premature death in a manner similar to the Ctnnb1;Pten-mutant mice. Microarray and reverse transcription-PCR analyses revealed that gene regulatory processes induced by CTNNB1 were mostly enhanced by either KRAS activation or Pten loss in remarkably similar patterns and degree. The concomitant activation of CTNNB1 and KRAS in Sertoli cells also caused testicular granulosa cell tumors that showed gene expression patterns that partially overlapped those observed in GCTs of the ovary. Although the mutations analyzed herein have not yet been linked to adult GCTs in humans, they may be related to juvenile GCTs or to tumors in other tissues where CTNNB1 is mutated. Importantly, the results provide strong evidence that CTNNB1 is the driver in these contexts and that KRAS(G12D) and Pten loss promote the program set in motion by the CTNNB1.
WNT、RAS 或磷酸肌醇 3-激酶信号通路控制卵巢卵泡发育的特定阶段。为了分析这些通路在体内卵泡发育过程中在颗粒细胞中的功能相互作用，我们生成了特定的突变体小鼠模型。在颗粒细胞中稳定激活 WNT 信号效应物β-连环蛋白（CTNNB1）会导致形成良性肿瘤病变，这些病变在以后的生活中或在肿瘤抑制基因 Pten 被靶向删除后会自发发展为颗粒细胞瘤（GCT）。相反，表达致癌性 KRAS（G12D）会显著抑制颗粒细胞的增殖、分化和凋亡，结果是没有卵母细胞的小异常滤泡样结构在卵巢中积累。由于 KRAS（G12D）在颗粒细胞中具有强大的抗增殖作用，我们试图确定 KRAS（G12D）是否会阻止 CTNNB1 突变的卵泡中的癌前病变和肿瘤形成。出乎意料的是，转基因 Ctnnb1；Kras 突变小鼠表现出 GC 增殖增加、凋亡减少以及分化受损，并以类似于 Ctnnb1；Pten 突变小鼠的方式发生早期 GCT 导致过早死亡。微阵列和反转录-PCR 分析表明，CTNNB1 诱导的基因调控过程主要通过 KRAS 激活或 Pten 缺失以非常相似的模式和程度增强。Sertoli 细胞中 CTNNB1 和 KRAS 的同时激活也导致睾丸颗粒细胞瘤，其表现出的基因表达模式与卵巢 GCT 中观察到的部分重叠。尽管本文分析的突变尚未与人类成年 GCT 相关，但它们可能与青少年 GCT 或其他 CTNNB1 突变的组织中的肿瘤有关。重要的是，这些结果提供了强有力的证据，表明 CTNNB1 是这些情况下的驱动因素，并且 KRAS（G12D）和 Pten 缺失促进了 CTNNB1 启动的程序。
