Defining the role of ERK1 and ERK2 in Pancreatic Cancer

 描述(申请人提供)：胰腺癌是美国癌症死亡的第四大原因，预后很差，治疗选择有限。胰腺导管腺癌(PDAC)是这些病例中数量最多的。KRAS基因在95%以上的PDAC病例中发生突变，导致Raf-MEK-ERK丝裂原活化蛋白激酶(MAPK)通路的激活。大量实验证据表明，这种蛋白激酶级联通路在驱动依赖KRAS的PDAC生长中起着关键作用。尽管有这样的重要性，ERK驱动PDAC增长的机制仍然令人惊讶地没有解决。在Ras-Raf-MEK-ERK级联的每个水平上，都有结构和功能上相关的异构体。现在有强有力的证据表明，不同的RAS和Raf亚型在信号转导和癌症中的作用存在显著差异。对于两种高度相关的ERK1和ERK2亚型是否也是如此，这两种亚型拥有84%的序列同源性，仍未得到充分研究。我们目前对ERK生物学功能的大部分了解来自于对“ERK1/2”的研究，这些研究没有区分这两种亚型。此外，ERK1/2能够磷酸化200多个已知底物，但人们对这些底物中哪些是ERK/MAPK途径的重要驱动因素知之甚少。广泛的底物清单为关于哪些底物在胰腺癌的发展和维持中发挥积极作用的研究带来了进一步的复杂性。根据文献中的一些报道，ERK1和ERK2在某些情况下可能发挥不同的作用，我进行了初步的研究，以确定这两种异构体在PDAC中是否可以互换。我使用针对ERK1或ERK2的shRNA在10个PDAC细胞系中进行的研究表明，ERK1或ERK2的缺失既减少了锚定依赖的克隆生长，也减少了锚定非依赖的软琼脂生长，表明这两种高度相关的异构体都不能在功能上补偿另一种异构体的丧失。因此，我假设ERK1和ERK2在驱动KRAS突变的胰腺癌生长中具有不同的和非多余的作用。我提出了三个具体的目标来验证我的假设：我将(1)定义KRAS突变的PDAC生长对ERK1和ERK2的依赖；(2)定义PDAC上皮细胞中ERK1和ERK2在间质转化、侵袭和代谢改变中的作用；以及(3)确定PDAC中依赖ERK异构体的底物。这些研究将探讨ERK1和ERK2在胰腺癌中的不同和共享的功能，并有可能发现ERK MAPK通路中这一关键节点的新的信号机制。这项奖学金还将增强我的研究技能，在基础和转译癌症生物学方面奠定坚实的基础，并帮助我发展成为癌症研究领域的独立研究员的技能。

 DESCRIPTION (provided by applicant): Pancreatic cancer is the fourth leading cause of cancer deaths in the United States, with a poor prognosis and limited treatment options. Pancreatic ductal adenocarcinoma (PDAC) accounts for the greatest number of these cases. The gene KRAS is mutated in greater than 95% of PDAC cases, and this leads to the activation of the Raf-MEK-ERK mitogen-activated protein kinase (MAPK) pathway. Substantial experimental evidence implicates the key role of this protein kinase cascade in driving KRAS-dependent PDAC growth. Despite this importance, the mechanisms by which ERK drives PDAC growth remain surprisingly unresolved. At every level of the Ras-Raf-MEK-ERK cascade there are structurally and functionally related isoforms. There is now strong evidence for striking differences in the role of different Ras and Raf isoforms in signaling and cancer. Whether this is also the case for the two highly related ERK1 and ERK2 isoforms, which share 84% sequence identity, remains underexplored. Much of our current understanding of ERK biological function comes from studies on "ERK1/2" that did not distinguish between these two isoforms. In addition, ERK1/2 are capable of phosphorylating greater than 200 known substrates, but there is little understanding of which of these substrates are important drivers of the ERK/MAPK pathway. The extensive list of substrates causes further complexity for studies regarding which substrates play an active role in the development and maintenance of pancreatic cancer. Based on some reports in the literature suggesting that ERK1 and ERK2 may play different roles in certain circumstances, I performed preliminary studies to determine whether these two isoforms are interchangeable in PDAC. My studies using shRNA directed against ERK1 or ERK2 in a panel of 10 PDAC cell lines showed that loss of ERK1 or ERK2 reduced both anchorage-dependent clonogenic growth and anchorage-independent soft agar growth, indicating that neither of these highly related isoforms can compensate functionally for the loss of the other. Therefore, I hypothesize that ERK1 and ERK2 have distinct and nonredundant roles in driving KRAS-mutant pancreatic cancer growth. I propose three specific aims to test my hypothesis: I will (1) define the dependency of KRAS-mutant PDAC growth on ERK1 and ERK2; (2) define ERK1 and ERK2 roles in PDAC epithelial to mesenchymal transformation, invasion and metabolic alterations; and, (3) Identify ERK isoform-dependent substrates in PDAC. These studies will investigate the divergent and shared functions of ERK1 and ERK2 in pancreatic cancer and have the potential to discover novel signaling mechanisms of this critical node in the ERK MAPK pathway. This fellowship will also enhance my research skills, establish a firm foundation in basic and translational cancer biology and help develop my skills to become an independent investigator in cancer research.