Original Article
Copyright ©2012 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Nov 21, 2012; 18(43): 6226-6234
Published online Nov 21, 2012. doi: 10.3748/wjg.v18.i43.6226
Insights into erlotinib action in pancreatic cancer cells using a combined experimental and mathematical approach
Falko Lange, Katja Rateitschak, Christina Kossow, Olaf Wolkenhauer, Robert Jaster
Falko Lange, Katja Rateitschak, Christina Kossow, Olaf Wolkenhauer, Department of Systems Biology and Bioinformatics, University of Rostock, 18057 Rostock, Germany
Falko Lange, Robert Jaster, Department of Medicine II, Division of Gastroenterology, University Medicine Rostock, 18057 Rostock, Germany
Olaf Wolkenhauer, Stellenbosch Institute for Advanced Study, Wallenberg Research Centre at Stellenbosch University, Stellenbosch 7600, South Africa
Author contributions: Lange F and Rateitschak K contributed equally to this work; Wolkenhauer O, Lange F, Rateitschak K and Jaster R designed the study; Lange F performed the experiments; Rateitschak K and Lange F designed the mathematical model; Lange F, Rateitschak K, Kossow C, Wolkenhauer O, Jaster R analyzed the data; Jaster R and Lange F wrote the manuscript.
Supported by A grant of the Bundesministerium für Bildung und Forschung through the FORSYS partner program, No. 0315255; and the Helmholtz Society as part of the Systems Biology Network
Correspondence to: Robert Jaster, MD, Department of Medicine II, Division of Gastroenterology, University Medicine Rostock, E-Heydemann-Str 6, 18057 Rostock, Germany. jaster@med.uni-rostock.de
Telephone: +49-381-4947349 Fax: +49-381-4947482
Received: May 9, 2012
Revised: August 27, 2012
Accepted: September 12, 2012
Published online: November 21, 2012

AIM: To gain insights into the molecular action of erlotinib in pancreatic cancer (PC) cells.

METHODS: Two PC cell lines, BxPC-3 and Capan-1, were treated with various concentrations of erlotinib, the specific mitogen-activated protein kinase kinase (MEK) inhibitor U0126, and protein kinase B (AKT) inhibitor XIV. DNA synthesis was measured by 5-bromo-2'-deoxyuridine (BrdU) assays. Expression and phosphorylation of the epidermal growth factor receptor (EGFR) and downstream signaling molecules were quantified by Western blot analysis. The data were processed to calibrate a mathematical model, based on ordinary differential equations, describing the EGFR-mediated signal transduction.

RESULTS: Erlotinib significantly inhibited BrdU incorporation in BxPC-3 cells at a concentration of 1 μmol/L, whereas Capan-1 cells were much more resistant. In both cell lines, MEK inhibitor U0126 and erlotinib attenuated DNA synthesis in a cumulative manner, whereas the AKT pathway-specific inhibitor did not enhance the effects of erlotinib. While basal phosphorylation of EGFR and extracellular signal-regulated kinase (ERK) did not differ much between the two cell lines, BxPC-3 cells displayed a more than five-times higher basal phospho-AKT level than Capan-1 cells. Epidermal growth factor (EGF) at 10 ng/mL induced the phosphorylation of EGFR, AKT and ERK in both cell lines with similar kinetics. In BxPC-3 cells, higher levels of phospho-AKT and phospho-ERK (normalized to the total protein levels) were observed. Independent of the cell line, erlotinib efficiently inhibited phosphorylation of EGFR, AKT and ERK. The mathematical model successfully simulated the experimental findings and provided predictions regarding phosphoprotein levels that could be verified experimentally.

CONCLUSION: Our data suggest basal AKT phosphorylation and the degree of EGF-induced activation of AKT and ERK as molecular determinants of erlotinib efficiency in PC cells.

Keywords: Erlotinib, Pancreatic cancer, Epidermal growth factor receptor, Signal transduction, Mathematical modeling