Identification and characterization of S6K1 targets in mammary cell proliferation

描述（由申请人提供）：S6激酶1（S6K1）是细胞大小控制、蛋白质翻译和细胞增殖的重要调节因子，也是哺乳动物雷帕霉素靶标（mTOR）的最佳表征下游靶标之一。编码S6K1的基因RPS6KB1在高达30%的乳腺癌中扩增。在大多数RPS6KB1扩增的病例中，S6K1过度表达。 S6K1的过度表达与乳腺癌患者的不良预后相关。S6K1还介导乳腺癌细胞的雷帕霉素敏感性。具体目标旨在通过识别和表征乳腺癌细胞中S6K1的下游效应物，全面评估S6K1信号通路的治疗潜力。该提案的具体目标集中在S6K1通过鉴定乳腺癌细胞特异性S6K1效应物来控制细胞增殖的机制上。在目标1中，我们提出了一种生物化学方法结合质谱法用于鉴定S6K1的新型底物。在目标2中，我们将表征S6K1底物蛋白，并将绘制雷帕霉素敏感的磷酸化位点。在目标3中，我们将研究S6K1底物在乳腺细胞增殖控制中的作用。这项工作将促进S6K1及其下游效应物的新抑制剂在S6K1扩增肿瘤治疗中的后续开发。 公共卫生相关性：乳腺癌是女性癌症死亡的第二大原因。目前的化疗是不加选择的，具有毒副作用，并且在45%的患者中不能防止癌症进展或复发。本提案中描述的实验将使我们能够全面评估S6K1作为乳腺癌基因的作用及其在治疗这种疾病中的治疗潜力。

DESCRIPTION (provided by applicant): S6 kinase 1 (S6K1) is an important regulator of cell size control, protein translation and cell proliferation, and one of the best-characterized downstream targets of the mammalian Target of Rapamycin (mTOR). RPS6KB1, the gene encoding S6K1, is amplified in up to 30% of breast cancers. S6K1 is over expressed in the majority of cases with RPS6KB1 amplification. Over-expression of S6K1 correlates with poor prognosis in breast cancer patients. S6K1 also mediates rapamycin sensitivity of breast cancer cells. The specific aims are designed to provide a comprehensive assessment of the therapeutic potential of the S6K1 signaling pathway by identifying and characterizing downstream effectors of S6K1 in breast cancer cells. The specific aims of this proposal focus on the mechanism by which S6K1 controls cell proliferation by identifying breast cancer cell specific S6K1 effectors. In Aim 1, we propose a biochemical approach coupled with mass spectrometry for identification of novel substrates of S6K1. In Aim 2, we will characterize S6K1 substrate proteins, and will map rapamycin-sensitive phosphorylation sites. In Aim 3, we will study the role of S6K1 substrates in control of breast cell proliferation. The proposed work will facilitate subsequent development of new inhibitors of S6K1 and its downstream effectors in treatment of tumors with S6K1 amplification. PUBLIC HEALTH RELEVANCE: Breast cancer is the second leading cause of cancer death in women. Current chemotherapies are indiscriminate, have toxic side effects, and in 45% of patients do not prevent cancer progression or recurrence. The experiments described in this proposal will allow us to comprehensively evaluate the role of S6K1 as a breast cancer oncogene and its therapeutic potential in the treatment of this disease.