The effects of neurotensin and epidermal growth factor upon ERK-, Akt- and EGFR-phosphorylation in cells from the pancreatic adenocarcinoma cell line Panc-1

Abstract

In this paper we have used western blotting to study the phosphorylation of the intracellular enzymes ERK (MAPK) and Akt as well as the EGF receptor in response to stimulation with neurotensin (NT) and epidermal growth factor (EGF). Both these substances activate signaling cascades frequently overactive in cancer. Cells from the Panc-1 cell line, which is derived from a human ductal pancreatic carcinoma, have been used in our experiments. Previous studies have investigated ERK activation in these cells, but little is reported about Akt (PKB) phosphorylation in response to NT stimulation. We wanted to see whether or not NT induced transactivation of the EGF receptor and we also studied the effect of preincubation with different inhibitors in order to elucidate by which mechanisms EGF- and NT-induced phosphorylation occur. Finally, we stimulated our cells with thapsigargin or tetradecanoyl phorbol acetate (TPA) to investigate the effect of increased intracellular calcium and activation of protein kinase C (PKC), respectively. Results: EGF and NT stimulated ERK- and Akt-phosphorylation in a dose dependent fashion. EGF also stimulated EGFR phosphorylation dose dependently. We detected no NT-induced transactivation of EGFR. NT- and EGF-induced Akt activation was not mediated through PKC or increased intracellular calcium. NT-induced ERK activation seemed to be PKC-dependent, whereas EGF- induced ERK activation was reduced by 50% when inhibiting PKC.