Abstract 797: Gemcitabine resistant pancreatic cancer cell lines acquire an invasive phenotype with characteristics of EMT

Abstract

Abstract Gemcitabine is currently the standard first line treatment for patients with pancreatic cancer, however overall survival remains poor, and few options are available for patients that fail gemcitabine therapy. To identify potential molecular targets in gemcitabine refractory pancreatic cancer, we have developed gemcitabine resistant cell lines. Resistant cells were obtained by continuous exposure of MiaPaCa2 (MP) cells with increasing concentrations of gemcitabine. Stable cell lines were obtained with up to 500-fold resistance to gemcitabine. Characterization of the drug resistance cell lines has demonstrated no significant changes in gemcitabine uptake or metabolic pathways. The growth rate and doubling time of the drug resistant cell line is very similar to the parental drug sensitive cells with only small differences in response to gemcitabine. Cross resistance profiles demonstrate approximately 100-fold cross resistance to pyrimidine nucleoside cytarabine, but no resistance to the same in class agents, azacytidine and decitabine. Similarly, the gemcitabine resistant (GR) cell line displays 20-fold and 10-fold cross resistance to the purine nucleosides clofarabine and cladribine, respectively, but no differential response to fludarabine. Cell morphology of the drug resistant cells demonstrates characteristics of an epithelial-mesenchymal transition (EMT). Similarly, the GR cells are 5-fold more invasive in matrigel assays in vitro, and are significantly more aggressive in vivo. Microarray analysis demonstrated induced expression of several signaling pathways associated with EMT, including c-kit, TGFβ, and the JAG1/Notch axis. These data suggest that the primary mechanism of gemcitabine resistance is not related to alterations in drug uptake or metabolism, rather, the phenotype may reflect the selection of an intrinsic mechanism of enhanced cell survival. They further support a relationship between chemoresistance and EMT, and provide evidence for molecular pathways that may emerge as therapeutic targets in refractory pancreatic cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 797. doi:1538-7445.AM2012-797