Extracellular DNA Contributes to Pancreatic Cancer Invasion and Metastasis
Jiaqi Shi, Fushi Wen, Alex Shen, Andrew Choi. University of Michigan, Ann Arbor, MI; University of Arizona, Tucson, AZ
Background: Pancreatic cancer is the fourth leading cause of cancer death in US due to metastasis. Inflammation has been shown to facilitate metastasis. Extracellular DNA (exDNA) is a newly discovered component for inflammation and was reported on cancer cell surfaces. Analysis of exDNA as potential diagnostic, prognostic or predictive biomarkers for cancer indicated that their concentrations in the circulation are higher in cancer than in normal conditions. However, whether exDNA contributes to pancreatic cancer invasion and metastasis is not known.
Design: We used DNA fluorescent dye or antibody to detect exDNA. Using DNase I to digest exDNA, MTT, migration and invasion assays, we examined whether exDNA affected pancreatic cancer cell viability and contributed to invasion and migration in vitro. Finally human pancreatic cancer plugs were implanted into mouse pancreas to determine whether exDNA impacts metastasis in vivo. Two groups of mice received either introperitoneal saline or DNase I (1 U/mouse). Tumor growth and metastasis were monitored noninvasively every week by bioluminescence imaging. Organs were harvested for histology and bioluminescence analysis to evaluate the presence of exDNA and tumor metastasis.
Results: We detected exDNA on the surface and in vicinity of cultured pancreatic cancer cells and metastasized pancreatic cancer tissue, but not on normal human pancreatic ductal epithelial cells or in adjacent normal tissue. The presence of cell surface exDNA or DNase I treatment did not affect cell viability or growth, which is important for using DNase I to study the role of exDNA in metastasis. We showed that DNase I treatment significantly reduced pancreatic cancer cell migration and invasion. Normal pancreatic cells were not affected. Finally, the orthotopic human pancreatic cancer xenograft mouse model showed that tumor burden and metastasis were significantly inhibited by DNase I treatment.
Conclusions: Our results strongly support the hypothesis that exDNA contributes to the invasion and metastasis of pancreatic cancer. The increased presence of exDNA in pancreatic cancer and its role in metastasis support its potential as a useful diagnostic, prognostic or predictive biomarker as well as therapeutic target for pancreatic cancer.
Monday, March 4, 2013 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 272, Monday Morning