Targeting the Pim 1 Protein Kinase to Overcome Resistance to AKT Inhibitors

描述（由申请人提供）：迄今为止，靶向信号转导通路用于开发新的前列腺癌疗法的成功受到随后耐药机制发展的限制。在几乎70%的转移性前列腺癌病例中发现的高度活化的AKT蛋白激酶是这种疾病治疗的重要靶点。该提案中的初步数据表明，向前列腺癌细胞系中添加AKT抑制剂诱导细胞表面受体酪氨酸激酶（RTK）的显著增加，所述细胞表面受体酪氨酸激酶（RTK）通过增加细胞AKT活性来限制这些抑制剂的活性。 重要的是，还证明了AKT抑制剂诱导Pim-1蛋白激酶，这是一种与前列腺癌发生和进展有关的酶。南卡罗来纳州医科大学的研究人员发现，通过siRNA或基因工程小鼠成纤维细胞敲低Pim-1将抑制AKT抑制剂诱导RTK的能力。使用由该研究小组开发的小分子Pim-1抑制剂，他们已经证明AKT和Pim-1抑制剂的组合协同阻断组织培养和软琼脂中的前列腺癌细胞生长，并显着抑制免疫抑制动物中肿瘤的生长。这些令人兴奋的结果导致了独特的假设，即AKT抑制剂治疗引起Pim-1导向的反馈回路，从而诱导RTK。因此，AKT和Pim抑制剂的组合可能会协同杀死前列腺癌。本提案的具体目标是通过以下方式增强靶向这两种途径的能力：1）理解AKT抑制剂诱导Pim-1的机制; 2）破译Pim-1如何调节RTK水平以及Pim-1的抑制如何抑制这些生长因子受体;和3）在基因工程动物模型中验证这一假设，并探索这种组合在杀死生长在前列腺中的前列腺癌中的活性。小鼠这些研究将确定RTK和诱导的Pim-1水平作为药物作用的中间标志物。拟议的研究设计将利用基因工程细胞培养模型，mRNA表达分析，染色质免疫沉淀，和一种新的组织重组模型。完成后，这些研究将显著加速Pim和AKT抑制剂联合治疗的开发，以靶向反馈抗性机制，该机制将控制对目前正在研究的前列腺癌治疗单药疗法的反应。

DESCRIPTION (provided by applicant): The success of targeting signal transduction pathways for the development of new prostate cancer therapies has been limited to date by the subsequent development of drug resistance mechanisms. Highly activated AKT protein kinase found in almost 70% of cases of metastatic prostate cancer are an important target for therapies in this disease. Preliminary data in this proposal demonstrate that the addition of AKT inhibitors to prostate cancer cell lines induces a marked increase in cell surface receptor tyrosine kinases (RTKs) that function to limit the activity of these inhibitors by increasing cellular AKT activity. Importantly, it is also demonstrated that AKT inhibitors induce the Pim-1 protein kinase, an enzyme that has been implicated in prostate cancer initiation and progression. Investigators at the Medical University of South Carolina have discovered that knocking down Pim-1 either by siRNA or genetically engineered mouse fibroblasts will inhibit the ability of AKT inhibitors to induce RTKs. Using a small molecule Pim-1 inhibitor developed by this team of investigators, they have demonstrated that the combination of an AKT and Pim-1 inhibitor synergistically blocks prostate cancer cell growth in tissue culture and soft agar, and markedly inhibits the growth of tumors in immunosuppressed animals. These exciting results lead to the unique hypothesis that AKT inhibitor treatment causes a Pim-1-directed feedback loop that induces RTKs. Thus, the combination of an AKT and Pim inhibitor likely will synergize to kill prostate cancer. The specific aims in this proposal are to enhance the ability to target both of these pathways by: 1) understanding the mechanism by which AKT inhibitors induce Pim-1; 2) deciphering how Pim-1 modulates RTK levels and how inhibition of Pim-1 suppresses these growth factor receptors; and 3) validating this hypothesis in genetically engineered animal models and exploring the activity of this combination in killing prostate cancer grown in mice. These studies will identify RTK and induced-Pim-1 levels as intermediate markers of drug action. The proposed study designs will make use of genetically engineered cell culture models, mRNA expression analysis, chromatin immunoprecipitation, and a novel tissue recombination model. When completed, these studies will markedly accelerate the development of combination therapies with Pim and AKT inhibitors to target feedback resistance mechanisms that would control responses to single agent therapies currently under investigation for the treatment of prostate cancer.