The RAS and P13K Pathways in Pancreatic Adenocarcinoma

Dana-Farber Cancer Inst, Boston MA

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Abstract

The focus of this project is characterize signal transduction pathways downstream of K-Ras that mediate the[unreadable] pathogenesis of pancreatic ductal adenocarcinoma (PDAC). Our working hypothesis is that K-Rasdependent[unreadable] activation of phosphoinositide 3-kinase (PI3K) plays a critical role in this cancer. We speculate[unreadable] that pathways downstream of PI3K play diverse biological roles at every step along the PDAC progression[unreadable] process?specifically effecting rapid cell proliferation, resistance to apoptosis, aggressive motogenic[unreadable] behavior and angiogenesis. Further we propose that the detailed identification of both the upstream and[unreadable] downstream components of this signaling network would provide information on critical targets for improved[unreadable] therapeutics. The activation state of components of the Ras/PI3K/Akt signaling pathway will be assessed in[unreadable] the various mouse models for multistage PDAC being developed in Project 1. These models include[unreadable] expression of mutant K-Ras in the pancreas in the context of germline loss of various tumor suppressor[unreadable] genes (INK4a/Arf, p53; and/or SMAD4). Phospho-specific antibodies will be utilized in western blots, tissue[unreadable] staining and cytoimmunoflourescence to define the activation state of protein kinases downstream of Ras,[unreadable] including ERK, AKT, tuberin, FOXO family members, p70S6K, S6 and 4EBP1 as a function of tumor[unreadable] progression in the mouse models that are generated and phenotypically characterized in Projects 1 and 4. In[unreadable] addition these same components will be evaluated in human tissues and cell lines available from the[unreadable] Biobank Core. The activation of these pathways will be compared to the genetic profiles determined in[unreadable] Project 1 in order correlate genomic perturbations with biochemical responses. A strong emphasis will be[unreadable] placed on how these activation events relate to increasing grades of PanIN and the tumor biological[unreadable] properties of advanced PDAC tumors including angiogenesis in collaboration with Project 3. This same[unreadable] analysis will be used to characterize the properties of potential PDAC cancer stem cells defined in Project 4.[unreadable] In addition, the requirement for PI3K signaling components for tumorigenic growth in human PDAC cell lines[unreadable] will be evaluated using inducible shRNA vectors. Finally, a rigorous genetic approach to assess the[unreadable] functional role of PI3K signaling in PDAC pathogenesis will be undertaken by crossing mice that are[unreadable] conditionally deficient in PI3K subunits to the aforementioned mouse models. The identification of the crucial[unreadable] mediators of K-Ras-dependent tumorigenesis across the well-defined tumor contexts will illuminate future[unreadable] drug targets and pinpoint the critical molecules underpinning the biological progression of this deadly[unreadable] disease.