Reversal of multidrug resistance by gefitinib via RAF1/ERK pathway in pancreatic cancer cell line.

Pancreatic cancer is a devastating malignancy, characterized by intrinsic or acquired resistance to conventional chemotherapies. Recent evidences suggest an involvement of tyrosine kinase pathway in the regulation of multidrug resistance (MDR) protein gene expression. The aim of this study was to test whether gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor could regulate the MDR protein gene expression and sensitize the resistant cancer cells to chemotherapy. The gene expression of MDR proteins (MRP1, MRP2, MRP3, and PGP) were evaluated by quantitative RT-PCR, and expression levels of various tyrosine kinases were investigated by quantitative RT-PCR and Western blot in pancreatic cancer cell line. MTT assay was used for evaluating the effect of chemotherapeutic agents. Chemotherapeutics induced drug resistance by regulating the gene expression of MDR proteins (MRP1, MRP2, and MRP3), and increased the gene expression of RAF1/ERK and the phosphorylation of ERK in pancreatic cancer Bxpc-3 cells. Gefitinib caused an inhibition of p-ERK tyrosine kinase activation in a dose-dependent manner, and reversed gemcitabine-induced RAF1/ERK gene expression and p-ERK activation. In addition, a reversal of MDR proteins gene expression was achieved by gefitinib, which sensitized resistant cells to gemcitabine. This study demonstrated that MDR of Bxpc-3 cell is involved in the RAF1/ERK tyrosine kinase pathway. Gefitinib reverses the MDR protein gene expression and restores sensitivity of resistant cells to gemcitabine via RAF1/ERK signaling pathway. Combination of gefitinib with conventional chemotherapeutic agents may offer a new approach for the treatment of patients with pancreatic cancer.