EGFR High Expression, but not KRAS Status, Predicts Sensitivity of Pancreatic Cancer Cells to Nimotuzumab treatment in vivo.

Nimotuzumab, a monoclonal antibody against EGFR, has been shown to be efficacious in the treatment of advanced pancreatic cancer, but its predictive marker has not been established. The present study was designed to investigate the impact of EGFR and KRAS status on the antitumor efficacy of nimotuzumab and to explore its underlying mechanism of action. EGFR expression levels of pancreatic cancer cell lines, BxPC3, Panc-1, and Patu-8988, were analyzed by Western blot and immunocytochemistry, and their KRAS status was determined by gene sequencing. Anti-tumor effect of nimotuzumab on the cell lines were evaluated by cell proliferation and apoptosis assays in vitro, and mouse xenograft model in vivo. The expression levels of related molecules in EGFR pathway and IL-6 were analyzed by Western blot, immunohistochemistry, and/or real-time PCR.BxPC3 cells had wild type KRASand high-level EGFR; Panc-1 cells had mutant KRAS (G13A) and low-level EGFR; and Patu-8988 cells had mutant KRAS (G12V) and high-level EGFR. Nimotuzumab did not affect cell proliferation or apoptosis in vitro. The growth of BxPC3 and Patu-8988xenografts were significantly inhibited by nimotuzumab, but not Panc-1 xenografts, compared with that of the control group. The expression of EGFR in BxPC3 and Patu-8988 xenografts was significantly reduced by nimotuzumab. Changes of p-EGFR and p-Erk expression were different between BxPC3 and Patu-8988 cells, while p-Akt was not significantly changed after nimotuzumab treatment in all three cell lines. The IL-6 expression levels in BxPC3 and Patu-8988 xenografts were higher than that in Panc-1 xenografts in the control group, and were significantly reduced by nimotuzumab treatment. Pancreatic cancer cells with EGFR high expression were more sensitive to nimotuzumab treatment in vivo, than those with EGFR low expression. KRAS status had no impact on anti-tumor efficacy of nimotuzumab in pancreatic cancer cells.