Abstract LB-366: Cryo-fluorescence tomography as a new tool in 3D visualization of tumor heterogeneity, metastatic proliferation and immuno-oncology
Authors: Brevard Mathew , Farhoud Mohammed , Dimant Hemi , Sahagian Gary , Rosenthal Eben , Nguyen Quang-De 
Published: August 2018

Abstract
Cryo-fluorescence tomography (CFT) is an imaging modality based on serial slicing with off-the-block fluorescence imaging and is capable of imaging a whole animal, producing a 3D dataset. This technique is also able to image isolated tumors at higher resolution either from rodent models, or human patients. It is a strong complement to traditional in vivo imaging techniques and fills in gaps these techniques leave such as MRI's lack of sensitivity and specificity or PET, SPECT and optical techniques lack of resolution. High value sections are also selectively identified and transferred to slide for further histology and co registration back to the whole sample data set in the many instances where a whole animal/organ microscopy data set is not feasible. In this study, we utilize CFT in several tumor models to track tumor microenvironment and heterogeneity, metastatic spread, and expression of specific markers in excised human tumors. A 4T1 mouse mammary tumor model expressing both luciferase and DsRed was used to study metastasis. CFT showed a complete account of metastatic disease in our subject animals when compared to bioluminescence imaging. The high resolution molecular 3D data is invaluable to measure tumor burden, even with very small tumors, and is supported with whole body white light imaging for anatomical landmarking. A unilateral intracranial inoculation with GL26-luc2 cells in a mouse model was imaged two weeks later with T1-weighted MRI and Gadolinium contrast. Additional bioluminescence was also acquired. The subjects were then injected with indocyanine green (ICG) and Angiosense680Ex prior to sacrifice and CFT imaging. The CFT data had very high specificity to the tumor and a very high correlation to the MRI meaning the 2 techniques are equally good at assessing tumor angiogenesis. Further fluorescent markers can also be employed in the CFT study to provide additional information on gene/protein expression or presence of immunologic factors as well. To investigate the translation potential of this technique we imaged clinical squamous cell carcinoma tumors resected under fluorescence guided surgery using Cetuximab-IRDye800. These samples were formalin fixed paraffin embedded (FFPE) prior to CFT. The heterogenous distribution of Cetuximab in the tumors is compared to pre-operative and operative images to assess tumor margin and characterization. CFT has proven to be a powerful technique for oncology investigations. This technique can characterize the 3D bio-distribution and localization of antibody drug conjugates, or diagnostic antibodies, across an entire sample. More complete and precise data sets fluorescent labeled CAR T cells or tumor associated macrophages can aid the development of immuno-oncologic therapies.
Citation Format: Mathew Brevard, Mohammed Farhoud, Hemi Dimant, Gary Sahagian, Eben Rosenthal, Quang-De Nguyen. Cryo-fluorescence tomography as a new tool in 3D visualization of tumor heterogeneity, metastatic proliferation and immuno-oncology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-366.