Abstract 1294: Suppression of uPA in chemo-sensitization and p53 regulation in pancreatic cancer cells

Abstract

Abstract Despite new knowledge of the molecular profile of pancreatic cancer and its precursor lesions, survival rates have changed very little over the last 40 years. The ability to predict which patients would benefit most from surgical intervention and/or chemotherapy would be a great clinical asset. Researchers have demonstrated that uPA is frequently present in a higher concentration in the serum of pancreaticobiliary cancer patients. It is known that uPA is involved in ECM degradation and has been correlated with malignant transformation of cancer cells. Emerging data have suggested that the capability of a tumor to grow and propagate is dependent on a small subset of cells within a tumor called cancer stem cells (CSCs) or cancer initiating cells. Under in vitro cell culture conditions, these cells possess sphere-forming ability, which is known to be one of the properties of CSCs. Interestingly, the significance of this sphere formation ability still remains unclear. Recent studies have demonstrated that these sphere-forming cells acquired chemoresistance to cisplatin. In the present study, as observed by FACS analysis, we show that a sub-population of MIA PaCa-2 and PANC-1 pancreatic cancer cells possess cancer stem cell properties. RNAi-mediated suppression of uPA in these cells retarded their tumor forming ability in a nude mouse model. We also observed that uPA-suppressed MIA PaCa-2 and PANC-1 cells, after supplementation with uPA protein regained their cancer stem cell phenotype and showed increased expression of Lhx-2. To determine whether these sub-population cells possess any chemoresistance, we treated these cells with varying concentrations of gemcitabine (0-1000 nM) and observed that these cells were resistant to gemcitabine even at the 1000 nM concentration. Further suppression of uPA using siRNA in these cells sensitized these cells to gemcitabine. In addition, to determine whether uPA has any transcriptional role, we examined whether uPA interacted with any known transcription factors we used a TF-protein array. We observed that uPA interacted with Hoxa-5 very strongly. To further determine whether the interaction of uPA with Hoxa-5 invokes any regulatory response, we used a p53 promoter known to possess Hoxa-5 binding regions to drive a Luciferace gene, both with and without the presence of uPA. We observed that uPA retarded p53 promoter activity. Finally, nude mice implanted with MIA PaCa-2 cancer stem cells were susceptible to gemcitabine treatment after uPA downregulation. Taken together, these results indicate that targeting uPA can sensitize chemoresistant pancreatic cells to gemcitabine. 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 1294. doi:1538-7445.AM2012-1294