Amphiregulin regulates the activation of ERK and Akt through epidermal growth factor receptor and HER3 signals involved in the progression of pancreatic cancer

Pancreatic cancer is one of the most lethal malignancies. Epidermal growth factor receptor (EGFR), HER3, Akt, and amphiregulin have been recognized as targets for pancreatic cancer therapy. Although gemcitabine + erlotinib has been the recommended chemotherapy for pancreatic cancer, the prognosis is extremely poor. The development of molecularly targeted therapies has been required for patients with pancreatic cancer. To assess the validation of amphiregulin as a target for pancreatic cancer therapy, we examined its expression in pancreatic cancer using real‐time PCR analyses and ELISA. We also measured the apoptotic cell rate using TUNEL assays. In addition, alterations in signaling pathways were detected by immunoblotting analyses. Treatment with gemcitabine, which reduced the cell viability and augmented the cell apoptotic rate, activated and subsequently attenuated ERK and EGFR signals. However, gemcitabine, paclitaxel, or cisplatin treatment enhanced the Akt activation, heterodimer formation of EGFR with HER3, and secretion of amphiregulin, indicating that the presence of gemcitabine promoted the activity of targeted molecules including amphiregulin, Akt, and HER3 for pancreatic cancer therapy. Combined treatment with an inhibitor for amphiregulin and gemcitabine, paclitaxel, or cisplatin induced synergistic antitumor effects, accompanied by the suppression of Akt and ERK activation. Blockade of amphiregulin suppressed the activities of EGFR, HER3, and Akt and the expression of amphiregulin itself. According to this evidence, combination chemotherapy of conventional anticancer drugs plus an inhibitor for amphiregulin would allow us to provide more favorable clinical outcomes for patients with pancreatic cancer. (Cancer Sci 2010; 101: 2351–2360)