Because metastatic pancreatic cancer cells can disseminate from the primary tumor during the earliest stages of cancer progression, long before (10 years) the patient becomes symptomatic, the majority of patients have advanced stage metastatic disease at the time of diagnosis. This and the fact that patients resist all form of conventional chemotherapy, pancreatic cancer has a dismal 5 year survival rate of less than 5%, and a median survival of 4-6 months. Clearly, to combat this devastating disease new biomarkers for early detection and new therapeutic targets directed at eliminating metastatic cells are urgently needed. In this regards, Pseudopodium-enriched Atypical Kinase One (PEAK1) is a newly discovered biomarker of human pancreatic cancer. PEAK1 is overexpressed in greater than 90% of patients and is a functional tyrosine kinase that drives pancreatic cancer progression making it a highly attractive therapeutic target. However, before this new kinase can be fully considered for therapeutic development, it is imperative to understand how it mediates cancer cell proliferation, migration and dissemination at the molecular level. Therefore, the objective of this proposal is to identify the signal transduction pathways responsible for PEAK1-mediated pancreatic cancer cell metastasis. Based on published and preliminary data, the central hypothesis to be tested is that PEAK1 kinase drives cancer progression and metastasis by assembling a triple tyrosine kinase scaffold consisting of Src, ErbB2, and PEAK1 kinase itself. This scaffold serves to amplify tyrosine kinase activity in the cell leading to activation of the canonical ErbB2/Src/p130CAS/c-CrkII/Rac/Pak1/MEK/ERK pathway, which modulates cytoskeletal and integrin functions to drive cell locomotion, invasion, and metastasis. The hypothesis will be specifically tested by introducing a series of genetic mutations in the effector domains of PEAK1 that uncouple it form the ErbB2/Src/p130CAS/c- CrkII/Rac/Pak1/MEK/ERK pathway.
In Aim 1, human pancreatic cancer cells will be depleted of endogenous PEAK1 then reconstituted with the PEAK1 effector mutants and tested for their ability to mediate cell proliferation, migration, and 3-D matrix invasion in vitro.
In Aim 2, thes same cells will be thoroughly tested in vivo for their metastatic abilities to form microtumors, invade living tissues, induce angiogenesis, enter and exit the vascular system, and colonize secondary tissues in the liver and lungs. Importantly, these studies will capitalize on an innovative approach that combines high resolution confocal microscopy with unique animal models (optically transparent zebrafish and chickens) that facilitate direct visualization of cells undergoing distinct steps in the metastastic cascade in unprecedented detail. The proposed work is highly significant because PEAK1's discovery and its contribution to pancreatic cancer research is the first step in the process that drives development of new therapeutics, which are greatly needed to treat this devastating disease. In conclusion, understanding the molecular details of how PEAK1 contributes to human pancreatic cancer is necessary because it is a possible new therapeutic target and clinical biomarker of disease progression.
The overall goal of this work is to determine at the molecular level how the novel tyrosine kinase PEAK1 mediates pancreatic cancer formation and its progression to metastatic disease. Human pancreatic cancer cells expressing PEAK1 with various domains and key phosphorylation sites mutated will be tested for their ability to mediate cell proliferation and invasion in vitro and in vivo using novel animal models of cancer metastasis.
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