Investigations into the role of cyclooxygenase-2 (COX-2) in pancreatitis and pancreatic cancer have been very limited. A recently generated transgenic mouse that over- expresses COX-2 under the control of a keratin 5 promoter, K5.COX-2, develops spontaneous pancreatitis leading to pancreatic adenocarcinoma that has many of the same histological and molecular characteristics as the human disease. This occurs with a 100% incidence and is fatal by 8 months of age. The major prostaglandin (PG) product, PGE2, binds to one or more of the 4 EP receptors. EP2 and EP4 are linked to adenylate cyclase causing an increase in cAMP and subsequent activation of protein kinase A (PKA) and phosphorylation of CREB. Preliminary data indicate that the cAMP/PKA/pCREB pathway is highly activated in pre-lesion pancreata of K5.COX-2 mice, however, the MAPK/Akt/NFkB pathway is also highly activated. We hypothesize that activation of both the cAMP/PKA/pCREB and MAPK/Akt/NFkB signaling pathways are required for a full neoplastic response as is the inflammatory response, and that inflammation is driving the metaplastic and neoplastic changes.
Aim 1 will determine the requirement for PG signaling through the cAMP/PKA/pCREB pathway for adenocarcinoma development by generating transgenic mice with inducible, targeted activated CREB on a wildtype background, and dominant negative (dn)CREB on the K5.COX-2 background.
Aim 2 will determine the critical involvement of MAPK/Akt/NFkB signaling in adenocarcinoma development through the use dnAkt/K5.COX-2 bitransgenic mice and the use of MAPK and NFkB inhibitors. Activation of c-Src, EGF receptors, Erk, Akt and NFkB will be assessed in wild type, pre-lesion and lesions from K5.COX-2 pancreata.
Aim 3 will determine whether prostaglandins are driving acinar metaplasia by elevating cytokines that then recruit leukocytes. The effect of inhibition of COX-2 with celecoxib, or of inhibiting cytokine synthesis with pentoxyfylline, on cytokine expression, inflammatory cell infiltration and the development of acinar metaplasia and pancreatic cancer will be assessed. The effect of inhibition of COX-2 or cytokine synthesis on inflammatory cell infiltration in established lesions will also be determined to assess whether this will prevent further progression or reversion of the disease.
The proposed studies are significant because pancreatic cancer is one of the most fatal of all human malignancies and the lack of good animal models has severely hampered research into its etiology, prevention and treatment. Because of the associations between chronic inflammation, COX-2 and human pancreatic cancer, it is likely that the proposed work will generate information on the signaling pathways and receptors that are critical determinants in pancreatic cancer development, which should be useful for guiding future studies on chemoprevention and therapy.
