Mouse Model for Human Pancreatic Ductal Adenocarcinoma

描述（由申请人提供）：大多数人类胰腺癌表现为胰腺导管腺癌（PDA）。尽管在过去的二十年中我们对胰腺癌（PC）遗传学的了解有所增加，但PC患者的5年生存率仍为5%。更好地了解转移和开发更有效的治疗方法是胰腺癌研究人员面临的两大挑战。癌基因KRAS和肿瘤抑制基因p16和SMAD4在人PDA中经常发生突变。我们将重点研究这3个基因在胰腺癌进展转移中的作用及其作为药物靶点的可行性。基于PDA的遗传学，我们开发了一种小鼠模型，该模型在胰腺中含有致癌Kras和失活p16 （p16/Kras/Pdx1小鼠）。我们已经证明p16/Kras/Pdx1小鼠会发生mPanIN（类似于在人类中观察到的癌前病变）、侵袭性癌症（类似于PDA）和100%的转移。我们的数据表明，p16失活和Kras激活在促进胰腺进展和转移方面协同作用，超越早期肿瘤发生。p16和Kras在胰腺癌进展中的持续参与支持它们作为有效的治疗靶点。此外，我们还证明了野生型Kras等位基因的逐渐丧失与小鼠和人类的转移有关，这表明野生型Kras可能是选择性失活的，因为它抑制了转移。在Aim 1中，我们将通过恢复或删除人类和小鼠胰腺癌细胞系中的野生型Kras等位基因来研究野生型Kras是否具有肿瘤抑制功能，并在体外和体内研究对细胞增殖和/或转移的影响。如果野生型Kras确实具有肿瘤抑制功能，这将影响未来针对Kras的药物设计。在Aim 2中，我们提出产生可诱导的p16敲入小鼠系（p16KI）。在p16/Kras/Pdx1小鼠胰腺肿瘤发生过程中暂时诱导p16表达的能力将使我们能够评估体内恢复p16是否是一种可行的治疗策略。最后，在Aim 3中，我们希望继续努力产生不涉及工程致癌Kras等位基因的新小鼠模型。人类PDA的一部分不携带KRAS突变。我们建议继续我们对Smad4lox/lox的表征；P48Cre / +;MT-TGFalpha小鼠已显示出mPanIN的发展前景，有可能发展为PDA。该模型将使我们能够了解不涉及KRAS突变的胰腺肿瘤发生，并测试EGFR靶向治疗。随着癌症治疗朝着靶向治疗的方向发展，对我们来说，了解我们设计的靶向基因和途径变得更加重要。除了进一步了解KRAS， p16和SMAD4在胰腺癌进展和转移中的作用外，该应用的成功将影响我们如何设计KRAS靶向治疗，为p16替代/恢复治疗和EGFR抑制剂治疗提供新的见解，并为人类胰腺癌研究提供新的小鼠模型。

DESCRIPTION (provided by applicant): The majority of human pancreatic cancer is presented as pancreatic ductal adenocarcinoma (PDA). Although we have increased our understanding of pancreatic cancer (PC) genetics in the past two decades, the 5-year survival of PC patients remains at 5%. Gaining a better understanding of metastasis and developing more effective treatments are two major challenges for pancreatic cancer researchers. Oncogene KRAS and tumor-suppressor genes p16 and SMAD4 are frequently mutated in human PDA. Our studies will focus on the roles of these 3 genes in pancreatic cancer progression and metastasis and their feasibility as drug targets. Based on the genetics of PDA, we have developed a mouse model that harbors an oncogenic Kras and inactivated p16 in the pancreases (p16/Kras/Pdx1 mice). We have shown that p16/Kras/Pdx1 mice develop mPanIN (precancerous lesions similar to those observed in humans), invasive cancer (similar to PDA), and metastasis at 100%. Our data demonstrate that p16 inactivation and Kras activation work synergistically in promoting pancreatic progression and metastasis, beyond early tumorigenesis. The continual participation of p16 and Kras in pancreatic cancer progression supports them as valid therapeutic targets. In addition, we also demonstrated progressive loss of the wild-type Kras allele is associated with metastasis in both mice and humans, suggesting that the wild-type Kras might have been selectively inactivated because it was inhibiting metastasis. In Aim 1, we will investigate if the wild-type Kras harbors tumor-suppressive functions by restoring or deleting the wild-type Kras allele in both human and murine pancreatic cancer cell lines and examine the impacts on cell proliferation and/or metastasis in vitro and in vivo. If wild-type Kras does have tumor- suppressive function, it would impact future drug design targeting Kras. In Aim 2 we propose to generate an inducible p16 knock-in mouse line (p16KI). The ability to induce p16 expression temporally during pancreatic tumorigenesis in p16/Kras/Pdx1 mice will allow us to evaluate if restoration of p16 is a feasible therapeutic strategy in vivo. Finally in Aim 3, we wish to continue our efforts of generating a new mouse model that does not involved an engineered oncogenic Kras allele. A portion of human PDA does not harbor KRAS mutations. We propose to continue our characterization of the Smad4lox/lox; P48Cre/+; MT-TGFalpha mice, which has shown promising development of mPanIN, which will likely progress to PDA. This model will enable us to understand pancreatic tumorigenesis that does not involve mutated KRAS and to test EGFR targeted therapies. As cancer treatments move toward target therapies, it is more important for us to understand the genes and the pathways that we design to target. In addition to further our understandings of the roles of KRAS, p16, and SMAD4 in pancreatic cancer progression and metastasis, the success of this application will impact how we design KRAS target therapies, provide new insights to p16 replacement/restoration therapies and EGFR inhibitor treatments, and offers new mouse models for human pancreatic cancer research. PUBLIC HEALTH RELEVANCE: Oncogene KRAS and tumor-suppressor genes p16 and SMAD4 are frequently mutated in human pancreatic cancer. Our studies will focus on the roles of these 3 genes in pancreatic cancer progression and metastasis and their feasibility as drug targets. These experiments will help us better understand the mechanism of metastasis and to develop more effective target therapies for pancreatic cancer patients.