Abstract 4287: Novel method of liver tumor detection and characterization using ultrasound-induced biomarker release
Authors: D'Souza Aloma L. , Yan Xinrui , Gambhir Sanjiv S. 
Published: May 2015

Abstract
Blood biomarkers can revolutionize early cancer detection by earlier detection of circulating tumor biomarkers. We have shown that cell membrane permeabilization by low frequency ultrasound can release biomarkers from tumor cells. We use this non-invasive method to increase the detectable blood biomarker level from orthotopic liver tumors in mice, allowing for tumor characterization. The ability to focus ultrasound enables localization of the biomarker-release site. This novel strategy could lead to the earlier characterization of unknown incidental lesions leading to earlier detection and localization of cancer.
METHODS: The colon cancer cell line LS174T transfected with the firefly luciferase2 reporter gene was used to produce liver tumors in nude mice. This cell line produces the biomarkers carcinoembryonic antigen (CEA) and cancer antigen 19-9 (CA-19-9), which were detected using an enzyme-linked immunosorbant assay. The liver tumors were produced by either injecting 3 million cells in matrigel or transplantation of a piece of previously established subcutaneous tumor into the liver. The tumor growth was followed using bioluminescence and size was measured using ultrasound. The liver was exposed to low frequency (1MHz) ultrasound for 6 minutes, serum was collected and biomarkers measured. The increase in serum biomarker was determined by the difference in pre and post-ultrasound-treatment levels. Control samples were from tumor-bearing mice not ultrasound treated. Cells in culture were treated with the low frequency and biomarker release studied with an increase in time (0, 10, 30 min).
RESULTS: Both the methods used to produce the liver tumors showed an 80% rate of tumor establishment within a week of implantation. The other 20% showed tumor growth at a slower rate. The transplantation of the previously established subcutaneous tumor piece showed a better control of the tumor size compared to the cells implanted. The tumors showed an exponential growth in three weeks (week-3 mean volume 0.815 cm3). The ultrasound treated tumors showed a significant increase in blood biomarkers released (CEA: p&lt;0.007, n=10; CA19-9: p&lt;0.002, n=6), when compared to controls. The cells in culture showed significant biomarker release (CEA and CA19-9 p&lt;0.05) when treated with ultrasound. Previously studied cell death has been shown to be below 5 % under all conditions.
CONCLUSIONS: Increase in biomarkers released from cells in culture and liver tumors was observed with ultrasound-treatment. This allows for characterization of tumors depending on the amplification of tumor specific blood biomarkers. This orthotopic liver model can be used to study tumor characterization as well as has implications in diagnostic monitoring of lesions and therapy. This novel method has a clear pathway for application of MR-guided focused ultrasound in characterization of incidental tumors, merging the fields of imaging and in vitro diagnostics.
Citation Format: Aloma L. D'Souza, Xinrui Yan, Sanjiv S. Gambhir. Novel method of liver tumor detection and characterization using ultrasound-induced biomarker release. [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 4287. doi:10.1158/1538-7445.AM2014-4287