Abstract 5228: Multi-modal in vivo imaging of breast cancer cells expressing dual reporters

We previously engineered tumor cell lines with bioluminescentmarkers and fluorescent proteins for whole animal imaging. In addition to conventional non-invasive tumor growth detection, these cells when harvested from animals can also be used to analyze cell-cell interactionsby immunohistochemistry. Moreover, fluorescent cells can be isolated using fluorescent activated cell sorting (FACS) for gene expression profiling. In this study, we used a mouse mammary gland tumor cell line 4T1 that was labeled with firefly luciferase and tdTomato fluorescent protein (4T1-luc2-tdTomato). The generated cell line was tested for in vitro signal stability with respect to bioluminescenceand fluorescence prior to injection into the animals. Tumor cells were implanted subcutaneously and monitored for tumor development by acquisition of bioluminescentand fluorescent images. In a separate study, 4T1-luc2-tdTomato cells were implanted orthotopically into mammary fat pads. Tumor growth was monitored and signals from the implantation sites were reconstructed into three dimensional images. In order to non-invasively detect bone metastases by 4T1-luc2-tdTomato cells, we applied both microCT and optical imaging. For this, an interchangeable imaging platform between an optical imager and microCT machine was developed. 4T1-luc2-tdTomato cells were injected into nu/nu mice by intracardiac injection. Bioluminescent imagingwas performed immediately to verify the injection of cells into the left ventricle. Fluorescent signals were not detected, likely due to the small number of cells in the secondary tumor sites. Animals demonstrating substantial whole body bioluminescencewere selected for further monitoring until post injection day 9. We found that bioluminescentsignals were located in the knee joint regions. For these animals, bioluminescentand X-ray images were also taken without changing the positions of the animals using the interchangeable platform. Bioluminescent imagesin the knee joints were reconstructed using a diffused luminescence imaging tomography algorithm. These images were then co-registered with microCT images. The results showed that bioluminescentsignals were colocalized within the joint area obtained by microCT. Moreover, high resolution images of the joints from these mice revealed bone erosionin the tibia induced by 4T1-luc2-tdTomato cells. These findings demonstrate that multimodal imaging can pinpoint the tumor lesions non-invasively. In addition, low dose microCT imaging can be used to acquire high resolution skeletal images longitudinally without inducing adverse effects on the animals. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5228. doi:10.1158/1538-7445.AM2011-5228