Proteolytic processing of cyclin E in breast cancer

在许多乳腺癌中，全长细胞周期蛋白E通过弹性蛋白酶介导进行翻译后修饰 在氨基末端的两个特定位点的蛋白水解切割，导致产生低分子量的 在细胞周期中具有增加的活性和对细胞周期蛋白依赖性激酶的抗性的低分子量（LMW）亚型 抑制剂的细胞周期蛋白E的低分子量形式是重要的，因为它们作为预后标志物在肿瘤的发生中起重要作用。 乳腺癌患者及其参与细胞周期途径。我们以前的研究表明， 在25-35%的乳腺癌患者中观察到低分子量形式的细胞周期蛋白E的表达， 这种表达与不良的临床结果密切相关。此外，我们还报告说， 低分子量形式的细胞周期蛋白E在功能上是高度活跃的，并且对p21和p27的抑制具有抗性。最近我们 开发了在乳腺中过度表达低分子量形式的细胞周期蛋白E的转基因小鼠。这些小鼠 发展出具有转移潜能的肿瘤。这项研究的核心假设是， 细胞周期蛋白E的低分子量形式的过度表达，而不是全长细胞周期蛋白E，与乳腺癌的发生直接相关。 癌症进展和转移，使乳腺上皮易于发生肿瘤。调查 本提案中概述的将提供关于LMW形式的细胞周期蛋白 E介导它们在乳腺肿瘤发生中的作用。具体而言，我们将：1）确定致癌 全长细胞周期蛋白E的潜力和弹性蛋白酶切割在介导低分子量细胞周期蛋白E诱导乳腺癌中的作用 肿瘤的2)确定细胞周期蛋白E的全长和LMW形式之间的生物化学差异。第三章 研究CDK 2在低分子量细胞周期蛋白E过表达介导的乳腺肿瘤形成中的作用。 乳腺，以及最后4）确定肿瘤维持和复发对细胞周期蛋白E的需求。 这项研究是创新的，因为它不仅研究了细胞周期蛋白E的低分子量形式是否 使乳腺上皮细胞易于发生肿瘤，而且细胞周期蛋白E相关的 下游改变导致体内肿瘤形成。总的来说，通过 拟议的研究可能对早期和晚期乳腺癌妇女具有巨大的临床意义 癌我们已经知道细胞周期蛋白E过度表达与患者预后不良相关;如果细胞周期蛋白E 过表达也使乳腺易于发生遗传不稳定性，从而导致肿瘤发生， 提示乳腺癌中低分子量形式的细胞周期蛋白E表达的致病功能。

In many breast cancers, full length cyclin E is post-translationally modified through elastase mediated proteolytic cleavage of two specific sites in the amino terminus, resulting in the generation of low molecular weight (LMW) isoforms that have increased activity in cell cycle and resistance to cyclin-dependent kinase inhibitors. The LMW forms of cyclin E are important because of their significant role as prognostic markers in breast cancer patients and their involvement in cell cycle pathways. Our previous studies have shown that the expression of the LMW forms of cyclin E is observed in 25-35% of patients affected with breast cancer and such expression correlates very strongly with poor clinical outcome. Additionally, we have reported that the LMW forms of cyclin E are functionally hyperactive and resistant to inhibition by p21 and p27. Recently we developed transgenic mice overexpressing the LMW forms of cyclin E in the mammary gland. These mice develop tumors with metastatic potential. Thecentral hypothesis of theproposed research, is that the overexpression of the LMWforms of cyclin E, and not thefull-length cyclin E, are directly related to breast cancer progression and metastasis, predisposing the mammary epithelium to oncogenesis. The investigations outlined in this proposal will provide details regarding the mechanism through which the LMW forms of cyclin E mediate their effects in mammary gland tumorigenesis. Specifically,we will: 1) Determine the oncogenic potential of full length cyclin E and the role of elastase cleavage in mediating LMW cyclin E-induced mammary tumors. 2) Identify the biochemical differences between the full length and LMW forms of cyclin E. 3) Investigate the role of CDK2 in breast tumor formation mediated by LMW cyclin E overexpression in the mammary gland, and lastly 4) determine the requirement of cyclin E for tumor maintenance and recurrence. The proposed research is innovative because it investigates not only whether the LMW forms of cyclin E predispose mammary epithelium to oncogenesis, but also the mechanism by which cyclin E-associated downstream alterations lead to tumor formation in vivo. Collectively, the information gained through the proposed studies could have tremendous clinical relevance for women with early stage and advanced breast cancer. We already know that cyclin E overexpression correlates with poor patient outcome; if cyclin E overexpression also predisposes the mammary gland to genetic instability leading to tumorigenesis it would suggest a causative function for the expression of the LMW forms of cyclin E in breast cancer.