Human pancreatic adenocarcinoma contains a side population resistant to gemcitabine

BACKGROUND: Therapy resistance remains one of the major challenges to improve the prognosis of patients with pancreatic cancer. Chemoresistant cells, which potentially also display cancer stem cell (CSC) characteristics, can be isolated using the side population (SP) technique. Our aim was to search for a SP in human pancreatic ductal adenocarcinoma (PDAC) and to examine its chemoresistance and CSC phenotype. RESULTS: A SP was identified in all PDAC samples, expanded and analyzed as first-generation xenografts. This SP was more resistant to gemcitabine than the other tumour cells as analyzed in vivo. Whole-genome expression profiling of the SP revealed upregulation of genes related to therapy resistance, apoptotic regulation and epithelial-mesenchymal transition. In addition, the SP displayed higher tumourigenic (CSC) activity than the other main tumour cell population (MP) as analyzed in vitro by sphere-forming capacity. CONCLUSION: We identified a SP in human PDAC and uncovered a chemoresistant and CSC-associated phenotype. This SP may represent a new therapeutic target in pancreatic cancer. Micro-array analysis was performed on SP and MP samples of 5 xenografts, grown from 5 different human PDAC samples.