Role of Dietary Zinc Transporter ZIP4 in Pancreatic Cancer

描述（由申请人提供）：胰腺癌（PC）在所有癌症中死亡率最高，是北美癌症相关死亡的第四大原因，总体五年生存率低于5%。因此，迫切需要在PC中发现新的分子靶点，以指导有效治疗的选择。本文提出的新概念是锌转运蛋白ZIP4调节PC细胞生长、肿瘤进展和存活，这表明ZIP4具有新的重要作用。我们还发现ZIP4在大多数PC标本和PC细胞系中都有不同程度的过表达。强制过表达ZIP4可促进PC细胞增殖和肿瘤生长。相反，在小鼠模型中，shRNA沉默ZIP4可抑制PC生长并提高存活率，这表明ZIP4是一个潜在的治疗靶点。我们的初步数据还表明，microRNA-224 （miR-224）在ZIP4过表达的细胞和异种移植物中下调，而在ZIP4沉默时上调。miR-224的潜在靶点凋亡抑制剂5 （apoptosis inhibitor 5, API-5）在ZIP4过表达的PC细胞中表达上调，在ZIP4沉默的PC细胞中表达下调，提示ZIP4介导的PC生长存在新的机制。我们假设ZIP4的异常表达通过miR-224/API-5通路在PC细胞生长和肿瘤进展中起关键作用，ZIP4可能是PC的一个新的治疗靶点。我们打算确定ZIP4的表达是否a)在K-Ras转基因小鼠模型中变化并与肿瘤进展相关，b)在K-Ras转基因小鼠模型中与锌水平相关。我们还将确定ZIP4过表达是否a)下调miR-224的转录，b)通过miR-224/API-5途径影响PC细胞凋亡。最后，我们将确定a)脂质体/ZIP4 shRNA治疗3个周期，b)脂质体/ZIP4 shRNA加吉西他滨联合治疗小鼠模型PC是否有效。本R01提案的新发现是，膳食锌转运蛋白ZIP4在大多数PC患者中过表达，并调节PC的生长和生存。这些研究将有助于我们通过分子方法了解ZIP4与PC进展的相关性。

DESCRIPTION (provided by applicant): Pancreatic cancer (PC) has the number one fatality rate of all cancers, and is the fourth leading cause of cancer-related deaths in North America, with an overall five-year survival rate less than 5%. Therefore, there is an urgent need to identify novel molecular targets in PC that could guide the choice of effective therapies. The novel concepts in this proposal are that a zinc transporter, ZIP4, regulates PC cell growth, tumor progression, and survival, which suggests a new and important role for ZIP4. We have also found that ZIP4 is overexpressed in majority of PC specimens and PC cell lines to varying degrees. Forced overexpression of ZIP4 increases PC cell proliferation and tumor growth. Conversely, silencing of ZIP4 by shRNA inhibits PC growth and increases the survival rate in a mouse model, suggesting that ZIP4 is a potential therapeutic target. Our preliminary data also demonstrate that microRNA-224 (miR-224) is downregulated in ZIP4 over-expressing cells and xenografts, and is upregulated when ZIP4 is silenced. A potential target of miR-224, apoptosis inhibitor 5 (API-5), is found to be upregulated in ZIP4 overexpressing PC cells and downregulated in ZIP4 silenced PC cells, suggesting a new mechanism of ZIP4-mediated PC growth. We hypothesize that the aberrant expression of ZIP4 plays a critical role in PC cell growth and tumor progression through the miR-224/API-5 pathway, and ZIP4 may be a novel therapeutic target for PC. We propose to determine whether the expression of ZIP4 a) varies in a K-Ras transgenic mouse model and correlates with tumor progression, b) correlates with zinc levels in a K-Ras transgenic mouse model. We will also determine whether overexpression of ZIP4 a) downregulates the transcription of miR-224, and b) affects PC cell apoptosis through the miR-224/API-5 pathway. Finally, we will determine whether a) 3 cycles of liposome/ZIP4 shRNA treatment, and b) combinational therapy of liposome/ZIP4 shRNA plus gemcitabine is effective on PC in a mouse model. The novel findings in this R01 proposal are that the dietary zinc transporter ZIP4 is over-expressed in majority of patients with PC and regulates PC growth and survival. The proposed studies will help us to understand the correlation of ZIP4 and PC progression by using molecular approaches. PUBLIC HEALTH RELEVANCE: Pancreatic cancer is the fourth leading cause of cancer-related deaths in North America, therefore, there is a pressing need for more effective diagnostic and treatment strategies. The novel finding in this proposal is that the dietary zinc transporter protein ZIP4 regulates pancreatic cancer growth, which assigns a new and important role for ZIP4. Our preliminary data support that hypothesis that ZIP4 might be a therapeutic target for pancreatic cancer, and this study will lead to meaningful advances for understanding this horrible disease.