Abstract 3375: In vivo passaging of primary pancreatic tumor enriches for stem cells and PEAK expression
Authors: Metildi Cristina A. , Kaushal Sharmeela , Kelber Jonathan , Wright Tracy , Snyder Cynthia S. , Klemke Richard , Hoffman Robert M. , Bouvet Michael 
Published: August 2012

Abstract
The aim of this study was to select a more aggressive variant of a human pancreatic cancer cell line by serially passaging primary pancreatic tumor in nude mice and to evaluate for changes in tumor morphology as well as expression of stem cell markers and PEAK. Mouse models of human pancreatic cancer were established by orthotopically injecting 1x106 brightly-fluorescent BxPC-3 RFP pancreatic cancer cells into nude mice. Mice were subsequently followed with weekly whole body imaging using the Olympus OV-100 Small Animal Imaging System to follow tumor progression and time to metastasis. When deemed premorbid, the mice were sacrificed and their abdomens exposed for intravital imaging. Primary pancreatic tumor, a periportal metastatic deposit and ascites were removed from the premorbid mouse to establish cell lines. One million cells of the passaged primary pancreatic cell line were then orthotopically injected into another set of nude mice. Serially passaging continued until the life-span of the mouse with tumor stabilized. We subsequently analyzed samples of primary and metastatic lesions from the serially passaged tumors for analysis of stem cell markers and PEAK expression. With serial in vivo passaging of tumor, we were able to generate a more aggressive variant of human pancreatic cancer cell line BxPC-3 that displayed a more rapid primary tumor growth and a shortened overall survival in mice harboring tumor. Overall survival decreased from a mean of 20 weeks in mice with the parental cell line (P0) tumor to 7 weeks in mice with third-passage primary (P3) tumor. Additionally, tumor take was more readily established with the more aggressive cell line and time to metastasis within the abdominal cavity was shortened despite implanting a consistent number of cells at each passage. While mice harboring the parental line did not demonstrate evidence of metastasis until approximately three months post implantation, mice with P3 tumor developed metastatic disease by the second month after implantation. Real-time PCR evaluation demonstrated enrichment of the stem cell population in P3 compared to the parental cell line (P0). While there was an ∼2.5-fold increase in CD24 and EpCAM markers in the P3 primary tumor, CD44 had a 4-fold increase. Furthermore, P3 primary tumor had a 4-fold increase in PEAK expression while the periportal metastatic lesion from a P3 primary tumor had a 5.5-fold increase in the expression of PEAK. Further understanding of these in vivo effects on tumor initiation, progression and metastasis can aide in discovery of effective therapies to treat this dismal disease.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3375. doi:1538-7445.AM2012-3375