Abstract 4961: Longitudinal bioluminescence imaging of primary versus abdominal metastatic tumor growth in orthotopic pancreatic tumor models in NOD/SCIDγ(-/-) mice

Abstract

Abstract Pancreatic ductal adenocarcinoma (PDAC) has a very poor prognosis and is currently the fourth leading cause of cancer death in the United States. The lethal nature of PDAC is strongly associated with metastases to distant organs. The purpose of the present study was to develop and validate noninvasive bioluminescence imaging methods for differentially monitoring the kinetics of primary and abdominal metastatic tumor growth in mouse orthotopic models of pancreatic cancer. A semiautomated maximum entropy segmentation method was implemented for the primary tumor region-of-interest (ROI), and a rule-based method for manually drawing an ROI for the abdominal metastatic region also was developed. The two ROI methods were first validated by having two observers independently construct ROIs for the tumors of animals implanted orthotopically with Panc-1 cells, and the results compared with the number of mesenteric lymph node metastatic nodules counted upon necropsy. The findings were extended to orthotopic tumors of the more metastatic MIA PaCa-2 and AsPC-1 cells where different groups of animals were implanted with different numbers of cells. When the data were expressed as the total photon flux (Ph/sec) in the ROIs for the primary tumor and metastases, the total flux within the metastasis ROI was larger in magnitude than the total flux from the primary tumor ROI, at times by as much as several orders of magnitude. However, when the data were expressed as the average flux density (Ph/sec*mm2) within the ROIs, the density of the flux within the smaller primary tumor ROI was larger in magnitude than the density of the flux from the larger metastasis ROI, by as much as several orders of magnitude. Interobserver assessments for total flux and flux density from ROIs for both the primary tumors and metastatic region were highly concordant, with correlation coefficients of r > 0.98, coefficients of variation of ≤ 0.02, and limits of agreement within <5%. Further, there were statistically significant differences in the growth kinetics of AsPC-1 and MIA PaCa-2 orthotopic tumors when mice were implanted with different numbers of cells for each cell line. The present results demonstrated that the segmentation methods were highly reliable, reproducible and robust, and allowed statistically significant discrimination in the growth kinetics of primary and abdominal metastatic tumors of different cell lines implanted with different cell numbers. Thus, primary tumors and abdominal metastatic foci in orthotopic pancreatic cancer models can be reliably monitored separately and noninvasively over time with bioluminescence imaging. The novel segmentation methods reported here will facilitate investigations of the biology of primary and metastatic tumor growth, as well as the effects of novel treatments, over time, in individual animals. Citation Format: Harlan E. Shannon, Melissa L. Fishel, Jingwu Xie, Dongsheng Gu, Brian P. McCarthy, Amanda A. Riley, Anthony L. Sinn, Jayne M. Silver, Mark R. Kelley, Helmut Hanenberg, Murray Korc, Karen E. Pollok, Paul R. Territo. Longitudinal bioluminescence imaging of primary versus abdominal metastatic tumor growth in orthotopic pancreatic tumor models in NOD/SCIDγ(-/-) mice. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4961. doi:10.1158/1538-7445.AM2014-4961