Proeolytic Processing of Cyclin E in Breast Cancer

描述（由申请人提供）：三阴性乳腺癌（TNBC）是浸润性乳腺癌的一个高度侵袭性亚组，约占所有病例的15%，定义为缺乏雌激素受体、孕激素受体和HER 2。TNBC患者治疗的改善可能来自于鉴定对TNBC的发展和维持至关重要的癌基因。最重要的是，新疗法不仅必须治疗肿瘤细胞的增殖群体，而且还必须治疗播散性肿瘤起始细胞的潜伏群体，这被假设为是复发和转移的原因。我们过去的工作已经确立了细胞周期调控蛋白在乳腺肿瘤的发生和增殖中的重要作用，重点是低分子量形式的细胞周期蛋白E（LMW-E）。我们实验室最近的工作表明，LMW-E形式在70%的TNBC中过表达，并与这些患者的不良预后相关。我们确定了LMW-E在肿瘤起始和增殖失调之外发挥作用的新方式，证明LMW-E在肿瘤进展中起作用。具体来说，我们已经确定了LMW-E在上皮-间质转化（EMT）的启动，转基因小鼠转移的产生和肿瘤起始细胞群的富集中的作用。下一个挑战是发展对LMW-E在这些过程中的机制理解，并确定LMW-E活性在阻断肿瘤进展中的治疗衰减的可行性。然而，我们不知道是否EL细胞周期蛋白E的上游途径的失调是起始事件。细胞周期蛋白E上游的关键蛋白之一是弹性蛋白酶，其切割EL细胞周期蛋白E以产生LMW-E。一个未回答的问题是，如果在肿瘤细胞中的弹性蛋白酶的失调是足以产生LMW-E引起的转化表型。拟议研究的中心假设是，弹性蛋白酶将EL细胞周期蛋白E蛋白水解加工为LMW-E，通过改变细胞周期蛋白E相互作用的伴侣和底物，异常激活导致诱导EMT和具有肿瘤启动潜力的细胞的信号传导途径，使乳腺上皮细胞易于发生肿瘤。以下目标旨在测试该假设的各个方面：目标1：确定诱导型转基因小鼠模型中肿瘤维持和复发对LMW-E时机和表达的要求，并与TNBC患者相关。目的2：探讨弹性蛋白酶对全长细胞周期蛋白E（cyclin E）的降解作用及其在乳腺肿瘤发生中的作用。目标3：通过鉴定和表征细胞质LMW-E的新结合蛋白和底物来研究LMW-E介导的致癌机制这些研究的成功完成将发展LMW-E表达在肿瘤发生中的后果的机制观点，并将我们的发现转化为临床。此外，我们的小鼠模型系统将为我们提供一个独特的系统，以检查在临床前体内环境中靶向TNBC的新型治疗剂的有效性。 公共卫生相关性：通过拟议的研究获得的信息可能对三阴性乳腺癌患者具有巨大的临床意义。我们已经知道LMW-E表达与TNBC患者预后不良相关;阐明LMW-E表达如何也可以改变细胞质信号转导途径，然后导致EMT和肿瘤发生，将开辟癌症治疗的新途径，可以利用靶向LMW-E的治疗策略。因此，对于目前没有此类治疗策略的患者，有针对性的个性化治疗是合理的。

DESCRIPTION (provided by applicant): Triple negative breast cancer (TNBC) is a highly aggressive subset of invasive breast cancer, accounting for approximately 15% of all cases and defined by lack of estrogen receptor, progesterone receptor, and HER2. Improvements in the treatment of TNBC patients will likely come from identifying the oncogenes critical to the development and maintenance of TNBC. Most importantly, new therapies must treat not only the proliferative population of tumor cells, but also latent populations of disseminated tumor initiating cells, which are hypothesized to be responsible for recurrence and metastasis. Our past work has established important roles for cell cycle regulatory proteins in the initiation and proliferation of tumors in the mammary gland, with an emphasis on the low molecular weight forms of cyclin E (LMW-E). Recent work in our laboratory has demonstrated that LMW-E forms are overexpressed in 70% of TNBCs and correlates with poor prognosis in these patients. We identified novel ways in which LMW-E functions beyond tumor initiation and deregulated proliferation, demonstrating that LMW-E has a role tumor progression. Specifically, we have identified roles for LMW-E in the initiation of the epithelial-mesenchymal transition (EMT), generation of metastases in transgenic mice, and enrichment of a tumor initiating population of cells. The next challenge is to develop a mechanistic understanding of LMW-E in these processes and determine the feasibility of therapeutic attenuation of LMW-E activity in blocking tumor progression. However, we do not know if deregulation of pathways upstream of EL cyclin E is the initiating event. One of the key proteins that is upstream of cyclin E is elastase, which cleaves EL cyclin E to generate LMW-E. An unanswered question is if the deregulation of elastase in tumor cells is sufficient to generate LMW-E giving rise to the transformed phenotype. The central hypothesis of the proposed research is that proteolytic processing of EL cyclin E to LMW-E by elastase predisposes mammary epithelium to oncogenesis by altering cyclin E interacting partners and substrates and aberrantly activating signaling pathways that lead to induction of the EMT and cells with tumor initiating potentials. The following aims are designed to test each aspect of this hypothesis: Aim 1: Determine the requirement of LMW-E timing and expression for tumor maintenance and recurrence in an inducible transgenic mouse model and correlate with TNBC patients. Aim 2: Investigate the role of proteolytic processing of full length cyclin E to LMW-E by elastase in mammary tumorigenesis. Aim 3: Examine the mechanism of LMW-E mediated oncogenecity through identification and characterization of novel binding proteins and substrates for cytoplasmic LMW-E The successful completion of these studies will develop a mechanistic view of consequences of LMW-E expression in tumorigenesis and translate our findings to clinic. Additionally, our mouse model system will provide us with a unique system to examine the effectiveness of novel therapeutics targeted to TNBC in a preclinical in vivo setting. PUBLIC HEALTH RELEVANCE: The information gained through the proposed studies could have tremendous clinical relevance for patients with triple negative breast cancer. We already know that LMW-E expression correlates with poor TNBC patient outcome; elucidating how the LMW-E expression can also alter the cytoplasmic signal transduction pathways which could then lead to EMT and tumorigenesis, will open novel avenues of cancer therapy that can take advantage of treatment strategies targeting LMW-E. As such, a targeted and personalized therapy can be justified for those patients who currently do not have such treatment strategies available to them.