N-3 Fatty Acid-Induced Akt Suppression: Chemoprevention for Pancreatic Neoplasia

描述(申请人提供)：几种癌症和一些侵袭前病变对w-3脂肪酸有反应，w-3脂肪酸在抑制细胞增殖的同时促进细胞凋亡。在胰腺癌中也有类似的反应，尽管胰腺正常和/或肿瘤细胞中w-3脂肪酸的抑制性质仍然是推测的。随着胰腺癌早期检测方法的出现，早期诊断将很快成为现实。因此，必须发展抗击这些癌前疾病的新方法，包括化学预防，即饮食中脂肪的摄取和关键信号通路的抑制可能会在早期癌症扩散之前减少其产生。为了检验这种可能性，有或没有表达激活的Kras的人胰腺导管上皮(HPDE)细胞和正常胰腺的小鼠以及那些发生突变的Kras诱导的胰腺癌前病变的小鼠将暴露于高水平的多不饱和脂肪酸(PUFAs)、w-3和w-6。观察正常组织和疾病进展过程中的细胞变化、细胞增殖和凋亡以及特定的分子事件(Akt的激活、PGE3结合的EP2对Akt激活的影响、Akt、FOXO和Bad等各种蛋白质的磷酸化)将确定w-3脂肪酸在这些建模系统中的作用机制。这项工作的前提是w-3脂肪酸将通过产生更高水平的PGE3来发挥作用，这将导致以EP2依赖的方式降低pakt。随后的下游事件包括FOXO和Bad的去磷酸化将促进细胞死亡的增加和细胞分裂的减少。这些评估的一部分将包括使用w-6脂肪酸作为对照，但也将阐明它们在这些建模系统中的潜在机制。体外操作将利用化学抑制或激活、siRNA技术和表达载体的转染，通过这一途径逐步抑制或增强各种信号。在体内，这项工作将在表达EP2、PI3K、COX-2、Akt、FOXO或Bad缺失的小鼠胰腺的突变Kras中完成。以这种方式，可以在途径的每一步进行系统和逐步的分析，以证明w-3脂肪酸、Akt途径和下游事件之间的直接和关键联系，这些下游事件改变了正常胰腺和癌前细胞的细胞增殖和诱导凋亡。了解培养的人类和小鼠胰腺细胞中的这些过程将阐明类似的饮食对人类胰腺癌前病变和癌症发展的影响，同时可能提供一种更有效的手段来抑制人类群体的早期疾病过程。

DESCRIPTION (provided by applicant): Several cancers and a few preinvasive lesions respond to w-3 fatty acids, which serves to promote apoptosis while blocking cellular proliferation. A similar response has been demonstrated in pancreatic cancer, although the suppressive nature of w-3 fatty acids in normal and/or neoplastic cells of the pancreas remains speculative. With the advent of modalities for earlier detection of pancreatic cancer, earlier diagnosis will soon be a reality. Hence, novel approaches to fighting these precancerous conditions must evolve, including chemoprevention, where dietary intake of fats and inhibition of key signaling pathways may reduce production of early cancer before it spreads. To examine this possibility, human pancreatic ductal epithelial (HPDE) cells with and without expression of activated Kras and mice with normal pancreas and those that develop mutant Kras-induced pancreatic precancer will be exposed to high levels of polyunsaturated fatty acids (PUFAs), w-3 and w-6. Observing cellular changes, cell proliferation, and apoptosis in normal tissue and during disease progression along with specific molecular events (activation of Akt, effects of PGE3-bound EP2 on Akt activation, phosphorylation of various proteins like Akt, Foxo, and Bad,) will determine the mechanisms of action for w-3 fatty acids in these modeling systems. The premise of this work is that w-3 fatty acids will function by generating increased levels of PGE3 which will lead to decreased pAkt in an EP2-dependent manner. Subsequent downstream events including dephosphorylation of Foxo and Bad will promote an increase in cell death and reduced cell division. Part of these evaluations will include employing w-6 fatty acids as controls but will also elucidate their potential mechanism in these modeling systems. In vitro manipulation will employ chemical inhibition or activation, siRNA technology, and transfection of expression vectors to suppress or enhance various signals in a stepwise manner through this pathway. In vivo, this work will be done in mutant Kras expressing mouse pancreas void of EP2, PI3K, Cox-2, Akt, Foxo, or Bad. In this manner, a systematic and stepwise analysis can be done at each step in the pathway to demonstrate a direct and critical link between w-3 fatty acids, the Akt pathway, and downstream events altering cell proliferation and inducing apoptosis in normal and precancerous cells of the pancreas. Understanding these processes in human cultured and mouse pancreas cells will illuminate similar dietary effects on human pancreatic precancer and cancer development while potentially providing a more effective means of inhibiting early disease processes in the human population.