Objectives Endoscopic pancreatic function tests are used to diagnose pancreatic diseases and are a viable source for the discovery of biomarkers to better characterize pancreatic disorders. However, pancreatic fluid (PF) contains active enzymes that degrade biomolecules. Therefore, we tested how preservation methods and time to storage influence the integrity and quality of proteins and nucleic acids. Methods We obtained PF from 9 subjects who underwent an endoscopic pancreatic function test. Samples were snap frozen at the time of collection; after 1, 2, and 4 hours on ice; or after storage overnight at 4°C with or without RNase or protease inhibitors (PIs). Electrophoresis and mass spectrometry analysis determined protein abundance and quality, whereas nucleic acid integrity values determined DNA and RNA degradation. Results Protein degradation increased after 4 hours on ice and DNA degradation after 2 hours on ice. Adding PIs delayed degradation. RNA was significantly degraded under all conditions compared with the snap frozen samples. Isolated RNA from PF-derived exosomes exhibited similar poor quality as RNA isolated from matched PF samples. Conclusions Adding PIs immediately after collecting PF and processing the fluid within 4 hours of collection maintains the protein and nucleic acid integrity for use in downstream molecular analyses.
Background: Pancreatic ductal adenocarcinoma (PDAC) has a dismal 5-year survival rate of 10% due to a lack of early detection and effective treatments. Aspartic protease Cathepsin E (CTSE) expression is increased early in PDAC, but its role in tumorigenesis is unknown. We hypothesize that high CTSE expression promotes proliferation, invasion, inhibition of apoptosis, and the secretion of cancer-associated cytokines in PDAC. Methods: Human PDAC cell lines (Mpanc96, Panc-1, and Miapaca2) were engineered to express high levels of CTSE. Cell proliferation, invasion, and apoptosis were analyzed and compared to control cell lines expressing low levels of CTSE. Cells were treated with aspartic protease inhibitors (Pepstatin A and Ritonavir) and monitored for proliferation (24 - 72 hours) and invasion (48 hours). Apoptosis was measured using propidium iodide and analyzed via flow cytometry. Conditioned media from cells was collected (72 hours) after treatment to assess differential secretion of cancer-associated cytokines using a cytokine array. Results: Proliferation was not affected by the overexpression of CTSE; however, inhibition of CTSE slowed proliferation in the Panc-1 and MiaPaca2, but not Mpanc96 cells. CTSE inhibitors promoted invasion of Mpanc96 and Panc-1, but not Miapaca2 cells, regardless of CTSE levels. Apoptosis was not significantly different between the cell lines treated with the aspartic protease inhibitors compared to controls. Increased expression of CTSE induced the secretion of various cytokines such as epithelial neutrophil-activating protein 78 (ENA-78), a chemokine expressed in inflammatory pancreatic disorders. Treatment with the inhibitor Pepstatin A decreased ENA-78 secretion. Conclusions: CTSE levels does not appear to affect proliferation or apoptosis; however, inhibition of CTSE increased cell invasion and resulted in altered cytokine secretion. Further studies examining how CTSE influences invasiveness, and cytokine secretion may create new opportunities for developing effective therapies for PDAC. Citation Format: Ericka Velez-Bonet, Sabrina Kaul, Corbin Pontious, Marcus Hong, Kelly Dubai, Zobeida Cruz-Monserrate. The role of Cathepsin E expression in pancreatic ductal adenocarcinoma tumorigenesis [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr PO-061.
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