Carcinoma of the pancreas is a devasting disease that is characterized by poor survival rates and unresponsiveness to chemotherapy. The molecular mechanisms that lead to malignant transformation of pancreatic exocrine cells and subsequent growth advantage are not known. However, cultured human pancreatic cancer cells overexpress the epidermal growth factor (EGF) receptor (EGFR), produce transforming growth factor-alpha (TGF-alpha), and commonly exhibit mutations in the K-ras oncogene and p53 tumor suppressor gene that may lead to aberrant transduction of EGFR-mediated signaling pathways. In contrast to EGFR, the receptors for insulin, insulin-like growth factor 1 (EGF-1), tumor necrosis factor (TNF), interferon-gamma (IFN), and acetylcholine are not overexpressed in these cells. In vivo, human pancreatic tumors overexpressed EGFR and four growth factors that activate EGFR: EGF, TGF-alpha, amphiregulin (AR) and heparin-binding EGF-like growth factor (HB- EGF). Therefore, in the present proposal they will test the hypothesis that excessive activation of EGFR may be of fundamental importance for the growth advantage of human pancreatic cancer cells. To test the hypothesis, they will use specific antisense oligodeoxynucleotides and/or antisense expression constructs to inhibit the expression of EGFR-activating growth factors in human pancreatic cancer cells, examine the effects of a dominant-negative EGFR construct and of a specific and potent inhibitor of EGFR kinase activity on the growth of these cells, study the growth characteristics and signal transduction pathways that are activated by EGF, TGF-alpha HB-EGF, and AR in these cells, conduct similar studies with Chinese Hamster Ovary (CHO) cells expressing various levels of wild-type EGFR and a novel variant EGFR in the absence and presence of mutated p53, and determine whether the fifth member of the EGF family, betacellulin, is also overexpressed in human pancreatic tumors. Because chronic pancreatitis (CP) has been associated with an increased incidence of pancreatic cancer, they will also study the expression of the EGF family of peptides in the pancreas of CP patients. CP may be associated with episodes of acute injury termed acute pancreatitis (AP). Therefore, they will also study the expression of EGFR and EGF-like peptides in the pancreas of acute pancreatitis (AP) patients and in a rat model of acute pancreatic injury. Because both cancer and CP are associated with altered acinar cell differentiation, they will delineate the role of EGFR in pancreatic differentiation by studying the effects of EGFR and TGF- alpha in AR42J cells, a well-differentiated cell with acinar characteristics. To this end, they will express wild type and variant EGFR and precursor and authentic TGF-alpha in AR42J cells, and characterize the growth of these cells in vitro and following injection into nude mice in vivo.
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