IRS-2 Function in Tumor Progression and Metastasis

描述（由申请人提供）：本提案的总体目标是研究胰岛素受体底物-2 （Insulin Receptor Substrate-2, IRS- 2）调节肿瘤细胞代谢促进乳腺癌进展和转移的机制。IRS蛋白是接合分子，被募集到活化的细胞表面受体，在那里它们组织信号复合物启动下游信号级联反应。许多通过IRS蛋白发出信号的受体与乳腺癌有关，这突出了了解这些细胞质分子如何影响肿瘤细胞功能的重要性。在人类中，IRS-1和IRS-2在正常和良性乳腺组织、DCIS和浸润性乳腺癌中均有表达。然而，这些接头蛋白在乳腺肿瘤进展中发挥不同的作用。具体来说，在缺乏IRS-2的情况下，转移明显受损，但在缺乏IRS-1的肿瘤细胞中，转移增强，但IRS-2的表达和激活增加。体外，IRS-2信号通路促进肿瘤细胞迁移、侵袭和存活。虽然IRS-1和IRS-2之间的功能差异已经确定，但这些高度同源的蛋白质在共同刺激下调节不同细胞结果的机制仍不清楚。为了预测IRS-1和IRS-2的相对表达对乳腺癌患者的影响，并确定如何操纵它们的表达和功能来干扰乳腺癌的进展，需要对这些接头蛋白进行额外的机制研究。申请人实验室最近的研究表明，IRS-2而非IRS-1在调节糖酵解促进肿瘤细胞生存和侵袭中发挥重要作用。此外，缺氧会增加IRS-2的表达，从而影响肿瘤的代谢状态，促进攻击行为。本研究的总体假设是IRS-2是一个重要的缺氧反应基因，通过调节肿瘤细胞代谢促进乳腺癌的进展和转移。为了验证这一假说，申请人拟：1)确定IRS-2调控乳腺癌细胞代谢的机制。IRS-2通过靶向激活PI3K/mTOR信号调节GLUT1的表面表达来增强葡萄糖摄取和促进有氧糖酵解的假说将被检验；2)探讨缺氧增强IRS-2表达的机制，明确其在乳腺癌代谢和进展中的功能意义。在低氧环境下，IRS-2的表达在基因转录水平上增加，以维持乳腺癌细胞的代谢，促进肿瘤的进展和转移，这一假设将被检验。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to investigate the mechanism by which Insulin Receptor Substrate-2 (IRS- 2) regulates tumor cell metabolism to promote breast cancer progression and metastasis. The IRS proteins are adaptor molecules that are recruited to activated cell surface receptors where they organize signaling complexes to initiate downstream signaling cascades. Many of the receptors that signal through the IRS proteins have been implicated in breast cancer, which highlights the importance of understanding how these cytoplasmic molecules impact tumor cell function. In humans, both IRS-1 and IRS-2 are expressed in normal and benign breast tissue, DCIS and invasive breast cancer. However, these adaptor proteins play divergent roles in mammary tumor progression. Specifically, metastasis is significantly impaired in the absence of IRS-2, but it is enhanced in tumor cells that lack IRS-1, but have increased IRS-2 expression and activation. In vitro, signaling through IRS-2 promotes tumor cell migration, invasion and survival. Although functional differences between IRS-1 and IRS-2 have been identified, the mechanism(s) by which these highly homologous proteins regulate distinct cellular outcomes in response to common stimuli remains unknown. To predict the consequences of the relative expression of IRS-1 and IRS-2 for breast cancer patients and to determine how their expression and function could be manipulated to interfere with breast cancer progression, additional mechanistic studies of these adaptor proteins are needed. Recent studies in the applicant's lab reveal that IRS-2, but not IRS-1, plays an essential role in regulating glycolysis to promote tumor cell viability and invasion. Furthermore, IRS-2 expression is increased by hypoxia, which impinges upon the metabolic status of tumors to promote aggressive behavior. The overall hypothesis to be examined in this proposal is that IRS-2 is an essential hypoxia-responsive gene that promotes breast cancer progression and metastasis through the regulation of tumor cell metabolism. To investigate this hypothesis, the applicant proposes to: 1) Determine the mechanism by which IRS-2 regulates metabolism in breast carcinoma cells. The hypothesis that IRS-2 enhances glucose uptake and promotes aerobic glycolysis through the targeted activation of PI3K/mTOR signaling to regulate the surface expression of GLUT1 will be examined; and 2) Investigate the mechanism by which hypoxia enhances IRS-2 expression and define the functional significance of this regulation for breast cancer metabolism and progression. The hypothesis that IRS-2 expression is increased in hypoxic environments at the level of gene transcription to sustain breast carcinoma cell metabolism and to promote tumor progression and metastasis will be examined.