UBAP2, A New Molecule in Pancreatic Cancer Progression

摘要胰腺导管腺癌是最具侵袭性的恶性肿瘤之一。 预后很差。不幸的是，80%-85%的患者被诊断为无法切除、无法治愈的晚期 疾病分期，中位生存期为6个月，总的5年生存率为5%。这很好 已知小GTP酶如K-RAS的激活突变在PDAC中几乎是普遍的，并且对 发病机制。不幸的是，即使经过30年的紧张调查，RAS仍然无法下药。在……里面 2013年，NCI开展了“RAS计划”，以进一步从分子水平了解RAS基因及其蛋白质 产品，在细胞信号中的作用和在健康和疾病中的功能，强调了确定 K-RAS激活的新分子调节剂可以用药并设计出新的治疗策略 改善PDAC患者的不良结局。在此上下文中，定义UBAP2(泛素绑定)的角色 相关蛋白2)，一种生物学功能未知的蛋白质，作为调节激活的分子开关 研究小分子GTP酶，如KRAS和胰腺癌中的巨噬细胞增多症，具有很高的创新性。 利用抗体-金纳米结合物作为唯一的诱饵，我们鉴定了UBAP2是其中的一种蛋白质 可能参与胰腺癌的巨噬细胞增多症。我们在初步数据中展示了 UBAP2的表达与PDAC患者总生存期的显著增加相关。我们也 证明UBAP2在转基因KPC胰腺癌细胞株和肿瘤组织中过表达 小鼠和PDAC患者。沉默UBAP2在体外和体内损害巨噬细胞吞噬功能，抑制增殖， 胰腺癌细胞体外迁移侵袭和体内肿瘤生长。从机制上讲，UBAP2 稳定小分子GTP酶的激活形式，包括rac1，cdc42和K-ras，并保护它们免受 退化。此外，与WAVE2和Arp2/3结合，UBAP2调制膜褶皱， 对液体相摄取至关重要。基于这些实验证据，我们假设UBAP2功能 作为一个分子开关，调节K-RAS等小GTP酶的激活，巨噬细胞吞噬和 胰腺肿瘤的发生。因此，确定UBAP2作为小GTP酶的关键调节因子的作用 激活和巨噬细胞吞噬作用将为利用UBAP2作为一种新的治疗方法提供独特的机会 针对过多的人类癌症，在这些肿瘤中，巨噬细胞吞噬和小GTP酶激活起关键作用 角色。为了验证这一假设并实现总体目标，我们将使用以下具体目标： 具体目的1：UBAP2调控的胰腺癌巨噬细胞吞噬的分子特征。 特异性目标2：UBAP2对小分子GTP酶激活的调节。 具体目标3：研究UBAP2在KRAS诱导的胰腺肿瘤发生中的作用。 目前的应用将建立UBAP2作为一种新的巨噬细胞吞噬调节器，解开一个独特的 KRAS激活机制及UBAP2在正常胰腺发育和胰腺发育中的作用 肿瘤发生学。这些研究将为靶向巨噬细胞吞噬和KRAS激活提供新的途径 即使在过去30年的紧张调查之后，这一点到目前为止仍然难以捉摸。

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies with a notoriously dismal prognosis. Unfortunately, 80-85% patients are diagnosed with an unresectable, incurable advanced stage disease putting the median survival at <6 months and the overall 5-year survival at <5%. It is well known that activating mutations of small GTPases such as K-RAS is near universal in PDAC and critical for pathogenesis. Unfortunately even after 3 decades of intense investigation RAS still remains undruggable. In 2013, NCI undertook “The RAS Initiative” to gain further molecular insight into RAS genes, their protein products, role in cellular signaling and functions in health and disease, underscoring a critical need to identify new molecular regulators of K-RAS activation that can be druggable and devise novel therapeutic strategies to improve dismal outcome in PDAC patients. In this context, defining a role for UBAP2 (Ubiquitin Binding Associated Protein 2), a protein of unknown biological function, as a molecular switch that regulates activation of small GTPases such as KRAS and macropinocytosis in pancreatic cancer is highly innovative. Using antibody-gold nanoconjugates as unique bait, we identified UBAP2 as one of the proteins potentially involved in macropinocytosis in pancreatic cancer. We demonstrate in our preliminary data low UBAP2 expression is correlated with significant increase in overall survival of PDAC patients. We also demonstrate that UBAP2 is overexpressed in pancreatic cancer cell lines and tumor tissues of transgenic KPC mice and PDAC patients. Silencing UBAP2 impairs macropinocytosis in vitro and in vivo, inhibits proliferation, migration and invasion of pancreatic cancer cells in vitro and tumor growth in vivo. Mechanistically, UBAP2 stabilizes the activated forms of small GTPases including Rac1, Cdc42 and K-RAS and protects them from degradation. Furthermore, in association with WAVE2 and Arp2/3, UBAP2 modulates membrane ruffling, critical for fluid phase uptake. Based on these experimental evidences we hypothesize that UBAP2 functions as a molecular switch that regulates activation of small GTPases such as K-RAS, macropinocytosis and pancreatic tumorigenesis. Therefore, establishing role of UBAP2 as a critical regulator of small GTPase activation and macropinocytosis will provide unique opportunities to exploit UBAP2 as a novel therapeutic target against a plethora of human cancers where macropinocytosis and small GTPase activation play a critical role. To test this hypothesis and achieve overall objectives, we will use following specific aims: Specific Aim 1: Molecular characterization of UBAP2 regulated macropinocytosis in pancreatic cancer. Specific Aim 2: Regulation of small GTPases activation by UBAP2. Specific Aim 3: Investigating a role of UBAP2 in KRAS driven pancreatic tumorigenesis. Present application will establish UBAP2 as a new regulator of macropinocytosis, unravel a unique mechanism of KRAS activation and define a role of UBAP2 in normal pancreas development and pancreatic tumorigenesis. These investigations will provide new avenues to target macropinocytosis and KRAS activation that remains elusive so far even after last 30 years of intense investigation.