Defining the role of ERK1 and ERK2 in Pancreatic Cancer

 描述（由申请人提供）：胰腺癌是美国癌症死亡的第四大原因，预后不良，治疗选择有限。胰腺导管腺癌（PDAC）占这些病例的最大数量。基因KRAS在大于95%的PDAC病例中突变，这导致Raf-MEK-ERK促分裂原活化蛋白激酶（MAPK）途径的激活。大量的实验证据表明，这种蛋白激酶级联在驱动KRAS依赖性PDAC生长中起关键作用。尽管如此重要，ERK驱动PDAC生长的机制仍然令人惊讶地未得到解决。在Ras-Raf-MEK-ERK级联的每个水平上，存在结构和功能相关的同种型。现在有强有力的证据表明，不同的Ras和Raf亚型在信号传导和癌症中的作用存在显着差异。这是否也是两个高度相关的ERK 1和ERK 2亚型的情况下，共享84%的序列同一性，仍然有待探索。我们目前对ERK生物学功能的理解大多来自于对“ERK 1/2”的研究，这些研究没有区分这两种亚型。此外，ERK 1/2能够磷酸化超过200种已知底物，但对这些底物中哪些是ERK/MAPK通路的重要驱动因素知之甚少。广泛的底物列表导致关于哪些底物在胰腺癌的发展和维持中起积极作用的研究进一步复杂化。基于文献中的一些报告表明，ERK 1和ERK 2可能在某些情况下发挥不同的作用，我进行了初步研究，以确定这两种异构体是否在PDAC中是可互换的。我在一组10个PDAC细胞系中使用针对ERK 1或ERK 2的shRNA的研究表明，ERK 1或ERK 2的缺失降低了锚定依赖性克隆生长和锚定非依赖性软琼脂生长，表明这些高度相关的同种型都不能在功能上补偿另一种的缺失。因此，我假设ERK 1和ERK 2在驱动KRAS突变胰腺癌生长中具有不同的非冗余作用。我提出了三个具体的目标来验证我的假设：我将（1）确定KRAS突变型PDAC生长对ERK 1和ERK 2的依赖性;（2）确定ERK 1和ERK 2在PDAC上皮间质转化，侵袭和代谢改变中的作用;（3）确定PDAC中ERK亚型依赖性底物。这些研究将探讨ERK 1和ERK 2在胰腺癌中的不同和共享功能，并有可能发现ERK MAPK通路中这个关键节点的新信号机制。该奖学金还将提高我的研究技能，在基础和转化癌症生物学方面建立坚实的基础，并帮助发展我的技能，成为癌症研究的独立调查员。

 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.