Abstract 5207: Targeting prion protein as a potential oncogene in pancreatic cancer.

Abstract

Abstract Background: Human prion protein (PrP) has been found to be up-regulated in gastric, breast, pancreatic cancers and its expression in cancer cells contributes to cancer progression and resistance to various cancer therapies. Current literature suggests that overexpression of PrP induces inherent resistance to cancer therapeutics, while repression of PrP induces sensitization to cancer therapeutics. Our previous studies using expression microarray have revealed that PrP is not detected in normal human pancreatic ductal cells but is expressed in human pancreatic ductal adenocarcinoma (PDAC) cell lines and 40% of pancreatic cancer specimens. Further, expression of PrP confers a worse prognosis in PDAC patients. The poor prognosis of pancreatic cancer demonstrates needs for better target and drug development. Our recent studies also found that PrP is universally expressed in fetal pancreatic precursor ductal cells, and co-expresses with pancreatic stem cell markers, such as Pdx1 and Notch1, suggesting that PrP is a marker of pancreatic stem cells and may cross-talk with Notch1 during development and pancreatic tumorigenesis. However, the role for PrP in the establishment or progression of cancer is unknown, and whether PrP cross-talks with oncogenes such as Notch in these processes need to be elucidated. Methods: We applied immunoprecipitation (Abcam, Anti-Prion protein antibody 8H4) and western blotting to investigate the binding partners for PrP. Knockdown and over-expression of PRNP gene were carried out on various pancreatic cell lines, followed by in vitro proliferation assay and apoptotic activity analysis of these cells. Results: Pancreatic cancer cell lines express different levels of PrP, e.g. BxPC3 and Pan02.03 have higher PrP expression when compared to Capan-1. Western blot analysis revealed that PrP can bind with Notch1 protein in both BxPC-3 and CAPAN-1 cell lines. Moreover, down-regulation of PrP led to decreased cell proliferation and accelerated apoptosis, accompanied by down-regulation of cleaved/activated Notch1 (ICN1) and Notch2 (ICN2) expression in BxPC3 cells, but had lesser effect on CAPAN-1 cells. In comparison, over-expression of PrP significantly increased the proliferation rate of CAPAN-1 cells and dramatically upregulated the expression of ICN1. In conjunction with our previous findings that PrP exists as a pro-prion that binds filamin A in pancreatic cancer cells, these findings suggest that PrP may mediate pancreatic cancer cell progression through regulation of Notch activity and other cell mechanic and signaling integrators. This hypothesis is being further tested by xenograft analysis. Elucidating the mechanisms for PrP mediated Notch activation in PDAC will further our long-term goal of understanding the role of oncogenic PrP in conferring pancreatic cancer aggressiveness, and potentially will lead to novel therapeutic options for treatment of pancreatic cancer. Citation Format: Yiwei Wang, Lan Zhou, Wei Xin. Targeting prion protein as a potential oncogene in pancreatic cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5207. doi:10.1158/1538-7445.AM2013-5207