PP5-ROLE OF A TRANSMEMBRANE PROTEASE, DIPEPTIDYL PEPTIDASE IN NEUROBLASTOMAS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。神经母细胞瘤（NB）是一种儿童肿瘤，起源于交感神经系统的前体细胞，已停止其正常分化程序。因此，与分化程序有关的因素在NB成因研究中具有重要意义。约70%患有广泛转移性或侵袭性局部肿瘤的儿童总体预后不良。证据，如通常只在胚胎和胎儿阶段表达的基因的表达，表明肿瘤是胚胎起源的。NB的分子机制尚不清楚。NB作为一种神经内分泌肿瘤，具有高水平的促瘤生长因子和肽激素表达。前体细胞向神经元的分化受生长因子和Notch信号通路的共同影响。Notch和生长因子相互作用在NB中的作用仍有待确定。细胞表面蛋白酶二肽基肽酶IV （dipeptidyl peptidase IV， DPPIV）是一种通过蛋白水解裂解调节多种神经肽和生长因子活性的分化抗原，其表达在许多癌症中缺失。我们最近表明，DPPIV降低碱性成纤维细胞生长因子bFGF的水平，bFGF是一种有效的有丝分裂原，抗凋亡和血管生成诱导剂。我们之前的工作提供了令人信服的证据，证明DPPIV作为一种肿瘤抑制基因，通过诱导分化和细胞凋亡，在前列腺癌、肺癌和黑色素瘤（一种神经外胚层起源的癌症）中发挥作用。有趣的是，DPPIV在哺乳动物神经元中表达，而在低分化的NBs中表达缺失。尽管有这些相关的观察结果，DPPIV在NB中的作用尚不清楚。我们的初步研究表明，DPPIV在NB衍生的细胞系中减少，DPPIV的重新表达导致分化表型的诱导。这些数据暗示了DPPIV在调控NB发育中的重要作用。本提案的目标是确定DPPIV在NB恶性表型中的作用，并确定与bFGF和Notch信号的联系（如果有的话），这些信号在神经元发育中起重要作用。综上所述，这些研究的结果代表了我们朝着建立包括DPPIV在内的丝氨酸蛋白酶调节NB衍生细胞分化程序和抑制癌性表型的关键途径的长期目标迈出的重要一步。假设：我们假设DPPIV是NB进展的负调节因子。我们预测DPPIV的缺失会导致bFGF水平的增加和Notch信号的激活，从而停止分化程序，并为NB细胞的增殖/存活和恶性转化提供生长刺激信号。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Neuroblastoma (NB) is a pediatric tumor that originates from precursor cells of the sympathetic nervous system that have discontinued their normal differentiation program. The factors implicated in the differentiation program are therefore of importance in the study of the genesis of NB. About 70% of children with widespread metastatic or aggressive localized tumors have overall poor prognosis. Evidence, such as expression of genes normally expressed only during embryonic and fetal stages, suggests that the tumor is of embryonic origin. Molecular mechanisms involved in NB are not well understood. As a neuroendocrine tumor, NB expresses high levels of growth factors and peptide hormones that exert tumor promoting effects. The differentiation of precursor cells into neurons is influenced by both growth factor and the Notch signaling pathways. The role of Notch and growth factor interaction in NB remains to be determined. The cell surface protease, dipeptidyl peptidase IV (DPPIV) is a differentiating antigen that regulates activity of many neuropeptides and growth factors by proteolytic cleavage, and its expression is lost in many cancers. We have recently shown that DPPIV decreases the levels of basic fibroblast growth factor bFGF, a potent mitogen, an anti-apoptotic, and an angiogenic inducer. Our previous work provides compelling evidence that DPPIV functions as a tumor suppressor gene for prostate cancer, lung cancer, and melanoma (a cancer of neuroectodermal origin) by inducing differentiation and apoptosis. Interestingly, DPPIV is expressed in mammalian neurons and its expression is lost in poorly differentiated NBs. Despite these correlative observations, the role of DPPIV in NB is unknown. Our initial studies show that DPPIV is decreased in NB derived cell lines and re-expression of DPPIV leads to induction of the differentiated phenotype. These data imply an important role for DPPIV in regulating the development of NB. The goal of this proposal is to define the roles of DPPIV on malignant phenotype of NB and to identify the link, if any, to bFGF and Notch signaling that play an important role in neuronal development. Taken together, the results from these studies represent an important step towards our long term goal of establishing pathways critical for modulating differentiation program and suppression of cancerous phenotype of NB derived cells by serine proteases including DPPIV. Hypothesis: We hypothesize that DPPIV is a negative regulator of NB progression. We predict that loss of DPPIV results in increased bFGF levels and activation of Notch signaling that halts the differentiation program, and provides growth stimulatory signals for proliferation/survival and malignant transformation of NB cells.