Abstract 2421: Extracellular DNA in pancreatic cancer metastasis

Abstract

Abstract Extracellular nucleic acids have received increasing attention for their potential application in the rapid, accurate, and non-invasive early detection of cancer and other diseases, but less attention is given to their potential roles in cancer biology. We initiated a study to examine the role of extracellular DNA in pancreatic cancer metastasis. Pancreatic cancer is one of the most lethal cancers with a prognosis of just six months to live, and a five-year survival rate less than 5%. This is mainly due to the fact that at the time of diagnosis, 80-90% of patients have metastatic cancer already. To better understand the metastasis mechanism of this cancer, we tested the hypothesis that pancreatic cancer cells produce extracellular DNA to promote their metastasis and cancer cell adhesion to a new micro-environment. We first examined the presence of extracellular DNA associated with pancreatic cancer cells by DAPI and CYTOX Green stains and by immunofluorescence assay (IFA) with the DNA-specific antibody. A large amount of extracellular DNA was observed on the surfaces and in the vicinity of the MiaPaCa-2 and BxPC3 pancreatic cancer cells but not the normal pancreas HPDE cells cultured on coverslips and in the 3D matrigel. A similarly larger amount of cell-free DNA was also found associated with the cancer cell line when the DNA from the cell culture media was extracted and analyzed. We subsequently stained tissue slides from human pancreatic cancer tissues, normal pancreas tissues, and the pancreatic cancer tissue microarrays using DNA-specific dyes and DNA -specific antibody in IHC and IFA. These experiments further confirmed the presence of extracellular DNA associated with the pancreatic cancer cells. To understand the role of extracellular DNA in cancer metastasis, we studied the effect of treatment with DNase I on cell migration, invasion, proliferation, and colonization in vitro. We measured cell adhesion to plates coated with adhesion proteins. We also investigated de-attachment of cells from coverslips by proteinase K in the presence or absence of DNase I. These functional studies showed DNase I inhibited cell migration, invasion, and adhesion without affecting cell viability. In the 3D matrigel, DNase I completely changed the pancreatic cancer cell growth pattern. We conclude that extracellular DNA associated with cancer cells play a novel role in cell migration, invasion, and cell adhesion in vitro. To our knowledge, this is the first report on the presence of a large amount of extracellular DNA on the surface and in the surrounding of pancreatic cancer cells and on the potential novel role of extracellular DNA in pancreatic cancer metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2421. doi:10.1158/1538-7445.AM2011-2421