Cellular Prion Protein Regulates Notch1 Expression in Pancreatic Ductal Carcinoma
Xueli Hao, Xiaoran Huang, Lihua Zhang, Lan Zhou, Wei Xin. University Hospitals Case Medical Center, Cleveland, OH; Case Western Reserve University, Cleveland, OH
Background: The Cellular Prion protein (PrP) is a GPI-anchored glycoprotein that is widely expressed on many normal cell surfaces. Over-expressions of PrP have been identified in many cancers including pancreas, breast, and colorectum. Our previous studies have found that PrP over-expression in PDAC patients was associated with a worse prognosis, as PrP enhanced PDAC invasiveness through binding with filamin A. Notch1 pathway plays an important role in cell proliferation, differentiation, and apoptosis in pancreatic organ development. The role of Notch1 in PDAC is controversial. Although one study suggested Notch might function as a tumor suppressor gene, many other studies suggested it promoted the development of pancreatic cancer. Inhibition of Notch signaling pathway has recently been explored as a therapeutic target for PDAC. In this study, we tested whether PrP interacts with Notch1 by using knockout cell lines.
Design: We used human PDAC cell line BxPC-3 with high expression of PrP (BxPC3-PrP-WT) and BxPC-3 cells after PrP shRNA treatment (BxPC-3-PrP-KO). PrP protein expressions in knockout cell lines were examined by Western blot. Gene array (Affymetrix GeneChip U133 plus 2.0 array) and flow cytometry were used to examine RNA and protein levels of PrP and Notch1 in these two cell lines.
Results: Knock-down of PrP via shRNA decreased PrP protein level by >90%. Consistently, there was an approximately 50% reduction of PrP mean fluorescent intensity (MFI) in PrP knock out (KO) pancreatic cancer cells compared with that of wild type (WT) cancer cells by flow cytometry. PrP KO cells showed a three fold reduction of Notch1 RNA compared with PrP WT cells by cDNA microarray analysis. This is further confirmed by our flow cytometric analysis that there was an approximately 50% reduction of cell surface Notch1 MFI in PrP KO cells compared with that of PrP WT cells.
Conclusions: Our data indicates that PrP up-regulates Notch1 expression in PDAC cell lines, and inhibition of PrP down-regulates Notch1 expression. It suggests that PrP may play an important role in the tumorigenesis of PDAC through regulation of Notch1 signaling, which provides a rationale for future study of this pathway as a novel therapeutic target for treating PDAC.
Monday, March 19, 2012 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 270, Monday Morning