Defining the roles of ERK MAPK in driving KRAS-mutant pancreatic cancer growth.

KRAS基因突变发生在~95%的胰腺导管腺癌(PDAC)中，并且是支持PDAC所必需的 成长。NCI已经确定，开发抗KRAS疗法是该领域的四个主要目标之一。 在目前的方向中，通过RAF-MEK-ERK丝裂原激活的KRAS效应器信号的抑制物 蛋白激酶(MAPK)级联反应已经显示出希望。我们的实验室最近证实ERK抑制剂是一种 PDAC的治疗策略前景看好。然而，正常的细胞毒性和肿瘤细胞的先天性/获得性耐药 可能会限制ERK抑制剂治疗的长期疗效。我的研究将挖掘两个未发表的组学数据 在我的实验室中生成的集合，以确定可能有助于克服这些限制的治疗策略。首先，在我的 Aim 1研究我评估了来自可药物基因组RNAi筛查的数据，以确定调节 PDAC对ERK特异性抑制剂SCH772984(ERKI)的敏感性。我选择了评估最热门的歌曲之一，CHEK1， 它编码CHK1丝氨酸/苏氨酸激酶。Chk1是检查点介导的细胞周期停滞所必需的，并且 DNA损伤后DNA修复的激活。因此，CHK1抑制剂更符合常规 与破坏DNA的抗癌药物相结合。然而，我决定同时治疗埃尔基和 临床候选CHK1抑制剂prexasertib增强了体外对PDAC生长的抑制作用。我的学习将会 确定Erki和prexasertib联合作为阻断KRAS的新策略的机制基础 依赖PDAC增长。虽然我已经确定了抑制MYC癌基因的收敛 功能，我还将应用反相蛋白质阵列(RPPA)分析来无偏地分析信号 转导活性/表达的变化为这一联合治疗提供了额外的机制洞察。我 还将在更严格的临床前模型中进一步评估这种组合的潜在治疗价值， 在患者衍生的有机化合物和原位PDAC小鼠模型中。其次，在我的Aim 2研究中，我评估了一个 RNA-seq数据集，分析ERK依赖的转录组，目的是识别驱动ERK的基因- 依赖PDAC增长。我找出了20个上调和下调最多的基因，其中Egr1是最多的一个 显著抑制了基因。Egr1是一种转录因子，与癌症有关，但作为 癌基因或抑癌基因，取决于评估的癌症类型。由于Egr1表达式是 抑制ERK，我已经确定Egr1调节MYC的表达，MYC是一个关键 依赖KRAS和ERK的PDAC增长的贡献者，我假设Egr1将是一个关键组件 ERK介导的基因表达。同时，我还将使用包含20个下调基因的RNAi筛查 建立一个更全面的鉴定促进ERK介导的PDAC生长的基因。我的 拟议的研究将有助于推进PDAC治疗的靶向ERK，并为我提供严格的 培训以提高我的计算/生物信息学技能。

KRAS mutations occur in ~95% of pancreatic ductal adenocarcinoma (PDAC) and are essential to support PDAC growth. The NCI has identified the development of anti-KRAS therapies is one of four major goals for the field. Among current directions, inhibitors of KRAS effector signaling through the RAF-MEK-ERK mitogen-activated protein kinase (MAPK) cascade have shown promise. Our laboratory recently validated ERK inhibitors as a promising strategy for PDAC treatment. However, normal cell toxicity and tumor cell innate/acquired resistance will likely limit the long-term efficacy of ERK inhibitor therapy. My studies will mine two unpublished omics data sets generated in my lab, to identify therapeutic strategies that may help overcome these limitations. First, in my Aim 1 studies I have evaluated data from a druggable genome RNAi screen to identify genes that modulate PDAC sensitivity to the ERK-specific inhibitor SCH772984 (ERKi). I chose to evaluate one of the top hits, CHEK1, that encodes the CHK1 serine/threonine kinase. CHK1 is required for checkpoint-mediated cell cycle arrest and activation of DNA repair in response to DNA damage. As such, CHK1 inhibitors are more conventionally combined with DNA damaging anticancer drugs. Yet I determined that concurrent treatment with ERKi and the clinical candidate CHK1 inhibitor prexasertib enhanced suppression of PDAC growth in vitro. My studies will determine the mechanistic basis for combining ERKi with prexasertib as a novel strategy to block KRAS- dependent PDAC growth. While I have already identified inhibitor convergence on blocking MYC oncogene function, I will also apply reverse phase protein array (RPPA) analyses for an unbiased profiling of signal transduction activity/expression changes to provide addition mechanistic insight on this combination therapy. I will also further evaluate the potential therapeutic value of this combination in more rigorous preclinical models, in patient-derived organoids and orthotopic PDAC mouse models. Second, in my Aim 2 studies, I evaluated an RNA-seq data set profiling the ERK-dependent transcriptome with the goal of identifying genes that drive ERK- dependent PDAC growth. I identified the 20 most up- and down-regulated genes, with EGR1 one of the most significantly suppressed genes. EGR1 is a transcription factor that has been implicated in cancer, but as either an oncogene or tumor suppressor, depending on the cancer type evaluated. Since EGR1 expression is suppressed upon ERK inhibition, and I have determined that EGR1 regulates expression of MYC, a key contributor to KRAS- and ERK-dependent PDAC growth, I hypothesize that EGR1 will be a critical component of ERK mediated gene expression. In parallel, I will also use an RNAi screen with the 20 downregulated genes to establish a more comprehensive identification of genes that contribute to ERK-mediated PDAC growth. My proposed studies will help advance targeting ERK for PDAC treatment as well as provide me with rigorous training to enhance my computational/bioinformatics skills.