Noriko Sato MD, Presenter: Nothing to Disclose

Omer Aras MD, Abstract Co-Author: Nothing to Disclose

Peter L. Choyke MD, Abstract Co-Author: Researcher, Koninklijke Philips Electronics NV Researcher, General Electric Company Researcher, Siemens AG Researcher, F. Hoffmann-La Roche Ltd Researcher, iCAD, Inc

The aim of this study is to examine the potential of a near-infrared (NIR) fluorescent probe with phosphstidylserin binding motif to visualize tumor killing effect of cytotoxic T cells in a murine immune cell therapy model.

A NIR probe PSVue 794 (Em 810 nm) binds to anionic phospholipids, including phosphatidylserine, via its zinc(II)-dipocilylamine motif. To examine if PSVue 794 allows visualization of cancer cell death induced by tumor specific cytotoxic T cells, adoptive transfer of CD8 T cells was employed in a mouse tumor model. CD8 T cells specific for obalbumin (OVA) were obtained from OT-1 T cell receptor transgenic mice. After labeling of OT-1 CD8 T cells with cell-permeable far-red DDAO dye (DDAO, Em 655nm) for tracking purpose, T cells were transferred to recipient mice bearing an intramascular OVA-expressing thymoma (EG.7) and the parental OVA-non-expressing thymoma (EL4) in the thigh. Twelve hours later, PSVue 794 (4mg/kg) was injected intravenously and optical images were acquired up to 5 days after the injection. Binding of PSVue 794 to apoptotic tumor cells was examined by double staining of the cells with fluorescein (FITC) -annexin V analyzed by flow cytometry.

Optical imaging demonstrated distribution of PSVue 794 to both EG.7 and EL4 tumors at 1.5hr, but showed a high specific accumulation in EG.7 tumor, the target of OT-1 CD8 T cells, at 24hr and at later time points. Migration of the DDAO labeled OT-1 T cells to the EG.7 tumor was observed at the same site. Imaging of tumor sections revealed the co-localization of PSVue 794 and DDAO within EG.7 tumors. Flow cytometry analysis of cells isolated from the tumors demonstrated the binding of PSVue 794 to the dead EG.7 tumor cells, which were also stained with FITC-annexin V. Collectively, PSVue 794 visualized EG.7 tumor apoptosis induced by cytotoxic effect of OT-1 CD8 T cells targeted the tumor.

A near-infrared optical probe PSVue 794 with an apoptotic cell binding capacity enabled visualization of tumor cell death induced by cytotoxic T cells in vivo in an immune cell therapy model. This is a unique imaging method to monitor functionality and therapeutic effect of adoptively transferred T cells.

Non-invasive in vivo imaging that allow us not only to track adoptively transferred cytotoxic T lymphocytes, but also to monitor the therapeutic effect, would contribute to the development and improve

Sato, N, Aras, O, Choyke, P, A Near-Infrared Probe Enables Optical Imaging of Tumor Killing by Cytotoxic T Cells in an Adoptive Immune Therapy Model.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11004853.html