Pancreatic ductal adenocarcinoma (PDAC) is a devastatingly lethal disease. The molecular mechanisms that dictate its biological aggressiveness are yet to be elucidated. We determined that PDAC tumor cells express high levels of the epidermal growth factor (EGF) receptor (EGFR) and related receptors (ErbB-2, -3, -4). We now hypothesize that excessive activation of the EGFR family contributes in a fundamental manner to the pathobiology of PDAD. To test this hypothesis, we will block receptor signaling through each member of this family in cultured pancreatic cancer cell lines, using a highly specific dominant-negative approach in conjunction with our recently established adenoviral gene delivery system. Signaling will next be blocked through multiple members of this family in order to determine which signaling pathways are attenuated by single versus combined receptor blockades, which pathways modulate mitogenesis and which confer resistance to anoikis. In vivo, we will assess effects of receptor blockade on tumor growth and metastasis in order to determine whether excessive activation of EGFR family signaling contributes to these biological characteristics of PDAC. To more clearly define the signaling components that mediate EGFR family actions, we will use dominant-negative constructs and chemical inhibitors to suppress specific downstream components of these pathways, and constructs encoding proteins that are active in a constitutive manner. To define novel signaling pathways that are modulated by EGFR, we will use Chinese hamster ovary cells that have a relatively normal gene background and that are devoid of endogenous EGFR, but that have been stably transfected with a cDNA encoding a wild type or variant human EGFR. We will thus gain insight into the biological roles of these highly homologous receptors with respect to mitogenesis, anoikis and invasiveness. To assess the potential for receptor heterodimerization in PDAC in vivo, we will use laser capture microdissection and quantitative polymerase chain reaction (PCR) to assay in the same cancer cells the levels of expression of all four members of the EGFR family. If we exclude gene amplification as a mechanism for in vivo overexpression, we will confirm that our cultured cell lines overexpress these receptors as a result of enhanced transcription in nuclear-run-on studies. We will then characterize their transcriptional control elements in order to develop second generation viral vectors that are preferentially targeted to pancreatic cancer cells.
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