Functional Study for Dlk1/Pref-1 on Tumor Angiogenesis of Neuroblastoma

Dlk1/Pref-1 was initially known as preadipocyte factor-1 (pref-1), functioning as an inhibitor of adipocyte differentiation in preadipocyte 3T3-L1 cells. It is a transmembranous protein belonging to the EGF-like homeotic superfamily that includes Notch receptor, its ligands, such as Delta, Serrate, and their mammalian homologues Dll and Jagged, as well as Dlk1/Pref-1. Notch signaling pathway is crucial in normal development and in tissue homeostasis, and it is recently found that Notch signaling is essential for vascular development and tumor angiogenesis. Blockade of the Notch ligand, Dll4, results in markedly increased tumour vascularity with enhanced angiogenic sprouting and branching. Paradoxically, the increased vascularity is non-productive by poor perfusion and the tumor growth is restricted. Neuroblastoma is a pediatric tumor with heterogeneous clinical presentation and courses. Angiogenesis has been known to play an important role for tumor growth in neuroblastoma and associated with advanced stages and aggressive outcomes. It is found that Notch signaling is related to cell differentiation and also contributes to angiogenesis in neuroblastoma. Although Dlk1/Pref-1 has been known to be highly expressed in a subset of neuroblastomas, its function in neuroblastoma has not yet been well understood. Recently, it was documented that Dlk1/Pref-1 acts as a negative regulator for Notch1 activation through interactions with specific EGF-like repeats. Moreover, our previous study has shown that Dlk1/Pref-1 is overexpressed in the endothelial cells of neuroblastomas. Hence, we hypothesize that the interaction between Dlk1/Pref-1 and Notch signaling may be crucial for tumor angiogenesis of neuroblastoma. In the pilot study, we have found that the recombinant extracellular domain of Dlk1/Pref-1 (Dlk1-EC) is able to promote cell proliferation and migration of endothelial cells in vitro in a dose-dependent manner. The in vivo study also demonstrated the positive neovascularization effect of Dlk1-EC-contained hydron pellets comparing to the control in rat eyes. To further understand the angiogenic effect of Dlk1/Pref-1 in neuroblastoma, we propose this project to perform both in vitro study in neuroblastoma cell lines and in vivo study in xenografted nude mice with overexpression and knockdown of Dlk1/Pref-1 to answer the following questions: 1) Is the angiogenic activity of the neuroblastoma cells affected by either overexpression or knockdown of Dlk1/Pref-1? 2) How is the interaction between the changes of Dlk1/Pref-1 expression and Notch signaling in the neuroblastoma cells? 3) How are the global mRNA changes of the neuroblastoma cells with overexpression or knockdown of Dlk1/Pref-1? 表C011 共2 頁第1 頁 4) Are the tumor growth and angiogenesis of neuroblastoma influenced by either overexpression or knockdown of Dlk1/Pref-1? 5) Are the neovascularized vessels productive if the tumor vessels are increased by either overexpression or knockdown of Dlk1/Pref-1? 6) How are the global protein changes of the xenografted neuroblastoma with overexpression or knockdown of Dlk1/Pref-1? The results of this study would be able to clarify the interaction between Dlk1/Pref-1 and Notch signaling and the role of Dlk1/Pref-1 in tumor angiogenesis of neuroblastoma. The information will be potentially helpful for the development of anti-angiogenic strategies for the treatment of neuroblastoma and other malignancies.

Project ID:PC9808-0540
External Project ID:NSC98-2320-B182-023-MY3