Pten/AKT and Siah in Regulation of Hypoxia

了解控制肿瘤发生和转移的潜在机制是 发展干预这些进程的手段。来自三个实验室的报告表明 Siah泛素连接酶(Siah1和Siah2)在胰腺、乳腺、黑色素瘤和前列腺癌中的作用 肿瘤的发展和/或进展。我们的研究揭示了Siah2在黑色素瘤中的作用 通过其对HIF和RAS信号通路的影响而发生和发展。通过监管 Pro羟基酶3稳定性，Siah2控制HIFIa的可用性和黑色素瘤细胞 转移，不影响致瘤性。通过调节Sprouty2(SPRY2)的稳定性，Siah2调节 RAS和Raf信号通路，它们决定了黑色素瘤的致瘤性。与这些一致 研究发现，Siah2在更多的转移性黑色素瘤中表达增加，这是通过分析 黑色素瘤TMA。 这些发现为研究潜在的调控和功能机制提供了理论基础。 黑色素瘤中的Siah2。我们的初步观察还表明，AKT调控Siah2的转录。我们 将阐明Akt介导的Siah2在黑色素瘤中表达增加的机制 50%的肿瘤含有具有结构性活性的Akt。 总而言之，我们的发现表明：(I)Siah2在恶性黑色素瘤中表达上调，(Ii) Siah2抑制通过SPRY2-RAS信号降低黑色素瘤的致瘤性；(Iii)Siah2抑制 AKT通过PHD3-HIF信号通路抑制黑色素瘤转移；(Iv)AKT调节Siah2 表情。总之，这些观察结果为我们的假设提供了基础，即在 控制AKT信号，Siah1/2在黑色素瘤的发生和发展中起核心作用。 转移。为了验证这一假设，我们将使用生物化学、分子生物学、细胞生物学和小鼠 模型以：(1)扩展我们最初的发现，定义了AKT依赖的潜在监管机制 以及(2)Siah2-Sprouty2相互作用与不同阶段的关系 黑色素瘤肿瘤的发展。我们还将(3)利用发生转移的TG-N-RAS/Alnk4a小鼠 黑色素瘤，以评估Siah的作用(以下与Siah1a‘’：Siah2“‘和Siah2”’：Siah1a*‘’ 在黑色素瘤的发生和发展中起重要作用。关于Siah2活动的其他研究 肿瘤的形成和转移将与项目2合作进行，以确定代谢 受Siah2和项目3影响的途径，其重点是确定和表征 Siah2抑制剂。总体而言，该项目应提供有关 Siah2在调节黑色素瘤发生和转移中的作用。

Understanding mechanisms underlying control of tumorigenesis and metastasis is central to development of means to intervene in these processes. Reports from three laboratories suggest that the Siah ubiquitin ligases (Siahl and Siah2) function in pancreatic, mammary, melanoma and prostate tumor development and/or progression. Our studies revealed the role of Siah2 in melanoma development and progression through its effect on HIF and Ras signaling pathways. By regulating prolyl hydroxylase 3 stability, Siah2 controls HIFIa availability and the ability of melanoma cells to metastasize, without affecting tumorigenicity. By regulating Sprouty2 (SPRY2) stability, Siah2 regulates Ras and Raf signaling pathways, which dictate melanoma tumorigenicity. Consistent with these findings, Siah2 expression increases in more mestastatic melanomas, as determined by analysis of melanoma TMA. These findings provide a rationale to investigate mechanisms underlying regulation and function of Siah2 in melanoma. Our initial observations also suggest that AKT regulates Siah2 transcription. We will delineate mechanisms underlying Akt-mediated increase of Siah2 expression in melanoma where 50% of tumors contain a constitutively active Akt. Collectively, our findings indicate that: (i) Siah2 expression is upregulated in malignant melanomas, (ii) Siah2 inhibition attenuates melanoma tumorigenicity through SPRY2-Ras signaling, (iii) Siah2 inhibition attenuates melanoma metastasis through PHD3-HIF signaling, and (iv) AKT regulates Siah2 expression. Together, these observations provide the foundation for our hypothesis that under the control of AKT signaling, Siahl/2 plays a central role In regulation of melanoma tumorigenesis and metastasis. To test this hypothesis we will use biochemistry, molecular biology, cell biology and mouse models to: (1) extend our original findings defining AKT-dependent mechanisms underlying regulation of Siah2 transcription, and (2) characterize Siah2-Sprouty2 interaction relevant to different stages of melanoma tumor development. We will also (3) utilize Tg-N-Ras/Alnk4a mice, which develop metastatic melanoma, to assess the role of Siah (following crosses with Siah1a'':Siah2"''and Siah2"'":Siah1a*'' mice) in melanoma development and progression. Additional studies addressing Siah2 activity in tumorigenesis and metastasis will be carried out in collaboration with Project 2 to identify metabolic pathways affected by Siah2 and with Project 3, which focuses on identification and characterization of Siah2 inhibitors. Collectively this project should provide new important information regarding the role of Siah2 in regulating melanoma tumorigenesis and metastasis.