Role of TTK/Mps-1 upregulation by Ral GTPase activation in pancreatic oncogenesis

描述（由申请人提供）：胰腺癌是一种致命的疾病，治疗方法很少。虽然在一些癌症的信号转导靶向治疗方面取得了成功，但尚未发现针对胰腺癌的显著靶向治疗方法。癌基因KRAS在约100%的胰腺癌导管腺癌（PDAC）中被突变激活。然而，开发K-Ras直接抑制剂的努力一直令人失望。因此，重点已转移到抑制效应信号级联激活

DESCRIPTION (provided by applicant): Pancreatic cancer is a deadly disease with few therapeutic options available. While success has been made in signal transduction-targeted therapies for some cancers, no significant targeted therapies have been identified for pancreatic cancer. The oncogene KRAS is activated by mutation in ~100% of pancreatic cancer ductal adenocarcinomas (PDAC). However, efforts to develop direct inhibitors of K-Ras have been disappointing. Therefore, focus has shifted to inhibiting the effector signaling cascades activated downstream of K-Ras. The canonical K-Ras effector pathways, Raf-MEK-ERK and PI3K-AKT-mTOR have received the most attention with >40 inhibitors of these two pathways currently under evaluation in clinical trials. However, recent studies investigating KRAS dependency and synthetic lethality argue that other effectors are key to K-Ras regulated transformation. The Ral guanine-nucleotide exchange factor (RalGEF)-Ral pathway is a non-canonical K-Ras effector pathway that have recently been validated for its importance in K-Ras-mediated oncogenesis. RalGEF activates the RalA and RalB Ras-like small GTPases. RalA regulates PDAC anchorage-independent growth in vitro and tumorigenesis in vivo, whereas RalB regulates invasion in vitro and metastasis in vivo. Transcription factor activation is a key consequence of Ral effector signaling. Therefore, we hypothesize that gene array profiling will identify key gene targets of Ral signaling, providing therapeutically useful avenues for drug discovery. Recently I performed gene array analyses and identified the gene encoding the dual specificity protein kinase TTK (also called Mps-1) as a transcript regulated by both RalA and RalB in PDAC. I also identified TTK mRNA overexpression in PDAC primary tumors and metastatic lesions compared to normal pancreas tissue. Furthermore, my preliminary studies have validated the requirement for TTK expression in PDAC anchorage-independent growth and Matrigel invasion in vitro. Thus, TTK may be an attractive and tractable target for anti-Ral and Ras drug discovery. In Aim 1, I will further validate the role of TTK in PDAC oncogenesis by using orthotopic tumor mouse models that better model the invasive and metastatic disease of the patient. In Aim 2, I will establish the importance of specific Ral effector signaling pathways for TTK expression and PDAC growth. RalBP1/RLIP76 and the Sec5 and Exo84 exocyst components are the best- characterized Ral effectors and I will determine if Ral mutants that differentially uncouple Ral from these effectors can rescue impaired TTK expression due to endogenous Ral silencing. Finally, Aim 3 studies will utilize missense and truncation mutants of TTK to investigate the requirement for kinase and non-kinase sequences in TTK function in PDAC anchorage-independent growth and invasion through Matrigel. Taken together, these studies will require me to master an array of experimental techniques, while preparing me to do both basic and translational research.