Background & Aims: The epidermal growth factor (EGF) receptor family and the corresponding ligands are frequently overexpressed in pancreatic cancer. To compare the biological effects of transforming growth factor (TGF)-α and amphiregulin (AR) on growth and differentiation of the exocrine pancreas, we have generated transgenic mice overexpressing AR under control of the elastase promoter. Methods: Two independently generated transgenic mouse lines overexpress 50-, 43-, 28-, 26-, and 16-kilodalton AR forms in the pancreas. Results: Morphologic and immunohistochemical examinations suggest that small intralobular duct and centro-acinar cells proliferate in response to AR in these mice. AR transgenic mice display increased Ras, Erk1/2, cyclin D/CDK4, and cyclin E/CDK2 activity and G1/S progression in pancreatic duct cells. In contrast to TGF-α transgenic mice, AR neither induced tubular complex formation nor elicited a strong fibrogenic response. AR induced a slight induction of ErbB2 on duct cells, whereas TGF-α resulted in overexpression of the EGF receptor in cells within tubular complexes. Furthermore, AR and TGF-α displayed different effects on differentiation of isolated acini in vitro comparable to the situation in vivo. Conclusions: These data suggest that AR induces a mitogenic response selectively in small duct cells through activation of Ras, CDK2, and CDK4, respectively. The closely related EGF receptor ligands, AR and TGF-α, display different biological effects when overexpressed in the exocrine pancreas in vivo.
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