Abstract 4200: Novel imaging strategy to assess the antitumor efficacy of treatments in an orthotopic mouse lung cancer model using ultrasound and photoacoustic imaging
Authors: Raes Florian , Sobilo Julien , Natkunarajah Sharuja , Trochet Philippe , Fuchs Dieter , Lerondel Stephanie , Le Pape Alain 
Published: July 2016

Abstract
Introduction
The aim of this study is to develop new strategies for the exploration of relevant preclinical lung tumor models dedicated to onco-pharmacology studies in mice. Here we refine a translational approach while overcoming physical ultrasound (US) imaging limitations allowing lung tumors exploration. Our data were compared to Computed Tomography (CT) and Bioluminescence (BLI) aiming to validate this promising approach.
Methods
Human lung cancer cells NCI-H460-luc2 were orthotopically xenografted in Balb/c nude mice. BLI was performed 7 days after implantation then once a week until the end of the study (Day 28) using an IVIS-Lumina II (Perkin Elmer). Tumors were imaged with the Vevo®LAZR System (FUJIFILM VisualSonics Inc.), 3D scans of US, Contrast Enhanced Ultrasound (CEUS) (Vevo MicroMarkerTM) and photoacoustic (PA) image being recorded digitally. A comparison between in vivo US and CT was achieved with additional ex vivo weight and volumetric measurements.
Results
The control of the tumor cell implantation was determined by BLI allowing the early quantification of tumor burden. 3D US measurements made possible longitudinal tumor volumes assessment. Compared to the other in vivo measurements, results clearly indicated the gross correlation of volumes processed with US and CT (R2 = 0.75). Such a correlation is also observed with ex vivo US weight and volumetric measurements (R2 = 0.72, R2 = 0.75 and R2 = 0.65 respectively). PA imaging evidenced the hemoglobin saturation with oxygen inside tumors, and targeted CEUS imaging allowed assessing the relative VEGFR2 expression in lung tumors.
Conclusions
This study proved the ability of US imaging to detect and control the in vivo orthotopic lung tumor growth. This real-time approach is fast while being completely inert regarding the in situ proliferation, as compared to dosimetry related to repeated CT examinations. Furthermore it allows overcoming the limitation of BLI at the time tumors become hypoxic since the luciferase/luciferin reaction is strictly dependent upon O2 and ATP. We described here a PA and US imaging strategy to follow the orthotopic lung tumors growth and consider biomarkers such as VEGFR2 expression or hypoxia in vivo for the first time. This procedure would be of great interest to longitudinally investigate tumor proliferation in animals when evaluating new anticancer therapies efficacy, avoiding any perturbation of the tumor progression compared to other available imaging modalities.
Citation Format: Florian Raes, Julien Sobilo, Sharuja Natkunarajah, Philippe Trochet, Dieter Fuchs, Stephanie Lerondel, Alain Le Pape. Novel imaging strategy to assess the antitumor efficacy of treatments in an orthotopic mouse lung cancer model using ultrasound and photoacoustic imaging. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4200.