Investigating the mechanism of CDCP1 activation to block CDCP1-driven metastasis

 描述（由申请人提供）三阴性乳腺癌（TNBC）是一种高度侵袭性和转移性形式的乳腺癌，其特征在于缺乏雌激素、孕酮和HER 2受体，这使得其对靶向和激素疗法具有抗性。TNBC患者往往年轻，因此，为这一亚组患者开发有效的靶向治疗的需求尤为迫切。TNBC的高转移潜力的分子基础是未知的。TNBC表达高水平的转移诱导蛋白，包含CUB结构域的蛋白1（CDCP 1），其与许多形式的癌症（包括TNBC）的侵袭性相关。 CDCP 1可以通过胰蛋白酶、间质蛋白酶和纤溶酶从全长135 kDa（flCDCP 1）蛋白水解加工成裂解的70 kDa（cCDCP 1）同种型。最近的报道强调了70 kDa cCDCP 1诱导的独特信号级联反应，包括粘附连接的降解、PARP 1介导的凋亡的逃避以及PKCδ、Akt和FAK信号的增强。此外，我们和其他人已经观察到，CDCP 1在多种TNBC细胞系中主要以裂解状态存在。 我们的实验室和其他人已经表明，CDCP 1被Src家族激酶（SFKs）磷酸化，这刺激了PKCδ向CDCP 1/SFK复合物的募集，导致PKCδ磷酸化。PKCδ激活导致细胞在体外迁移。目前尚不清楚磷酸化和切割是否是CDCP 1及其下游信号转导激活的唯一步骤。该项目的目的是剖析CDCP 1激活的机制，并确定一种策略来阻断它并抑制CDCP 1诱导的迁移。 我最近在HEK 293 T细胞中的工作显示，与flCDCP 1转染的细胞相比，cCDCP 1转染的HEK 293 T细胞中PKCδ、p38 MAPK、ERK 1/2和Akt磷酸化显著增加。这些发现支持CDCP 1裂解对其活化的必要性。此外，我发现只有cCDCP 1可以形成二聚体，我们建议通过已知参与蛋白质-蛋白质相互作用的CUB结构域进行。该二聚体在CDCP 1促迁移信号传导中的重要性仍有待研究。 这些研究旨在确定CDCP 1二聚体在CDCP 1介导的转移中的作用。我认为抑制CDCP 1二聚化是抑制CDCP 1介导的转移的基本治疗方法，因为目前FDA批准的一些抗癌疗法抑制其各自靶点的二聚化;赫赛汀、帕妥珠单抗和西妥昔单抗。

 DESCRIPTION (provided by applicant) Triple negative breast cancer (TNBC) is a highly aggressive and metastatic form of breast cancer that is characterized by a lack of the estrogen, progesterone, and HER2 receptor, which renders it resistant to targeted and hormone therapies. TNBC patients tend to be young, thus, the need to develop effective targeted therapies for this subgroup of patients is particularly urgent. The molecular basis for the high metastatic potential of TNBC is unknown. TNBC expresses high levels of a metastasis-inducing protein, CUB-domain containing protein 1 (CDCP1), which has been correlated with the aggressive nature of many forms of cancer, including TNBC. CDCP1 can be proteolytically processed from a full-length, 135 kDa (flCDCP1), to a cleaved, 70 kDa (cCDCP1), isoform by trypsin, matriptase, and plasmin. Recent reports have highlighted the unique signaling cascades induced by 70 kDa cCDCP1, which include degradation of adherens junctions, evasion of PARP1 mediated apoptosis, and enhancement of PKCδ, Akt, and FAK signaling. Furthermore, we and others have observed that CDCP1 exists mostly in the cleaved state in multiple TNBC cell lines. Our lab and others have shown that CDCP1 is phosphorylated by Src family kinase (SFKs), which stimulates the recruitment of PKCδ to the CDCP1/SFK complex, resulting in PKCδ phosphorylation. PKCδ activation results in migration of cells in vitro. It is not clear if phosphorylation and cleavage are the only steps in activation of CDCP1 and its downstream signaling. The objective of this project is to dissect the mechanism of CDCP1 activation and determine a strategy to block it and inhibit CDCP1-induced migration. My recent work in HEK 293T cells shows a dramatic increase PKCδ, p38 MAPK, ERK1/2, and Akt phosphorylation in cCDCP1 transfected HEK 293T cells, as opposed to flCDCP1 transfected cells. These findings support the necessity of CDCP1 cleavage for its activation. Furthermore, I found that only cCDCP1 can form a dimer, which we propose to occur through its CUB domains known to be involved in protein-protein interactions. The importance for this dimer in CDCP1 pro-migratory signaling remains to be investigated. These studies aim to determine the role of the CDCP1 dimer in CDCP1-mediated metastasis. I propose that inhibiting CDCP1 dimerization is a rationale therapeutic to inhibit CDCP1-mediated metastasis as some current FDA approved anti-cancer therapies inhibit dimerization of their respective targets; Herceptin, Pertuzumab, and Cetuximab.