Ex Vivo Radiolabeling and In Vivo PET Imaging of T Cells Expressing Nuclear Reporter Genes
Recent advances in T cell-based immunotherapies from bench to bedside have highlighted the need for improved diagnostic imaging of T cell trafficking in vivo and the means to noninvasively investigate failures in treatment response. T cells expressing tumor-associated T cell receptors (TCRs) or engineered with chimeric antigen receptors (CARs) face multiple challenges, including possible influence of genetic engineering on T cell efficacy, inhibitory effects of the tumor microenvironment, tumor checkpoint proteins and on-target, off-tissue toxicities (Kershaw et al., Nat Rev Cancer 13:525–541, 2013; Corrigan-Curay et al., Mol Ther 22:1564–1574, 2014; June et al., Sci Trans Med 7:280–287, 2015; Whiteside et al., Clin Cancer Res 22:1845–1855, 2016; Rosenberg and Restifo, Science 348:62–68, 2015). Positron emission tomography (PET) imaging with nuclear reporter genes is potentially one of the most sensitive and noninvasive methods to quantitatively track and monitor function of adoptively transferred cells in vivo. However, in vivo PET detection of T cells after administration into patients is limited by the degree of tracer accumulation per cell in situ and cell density in target tissues. We describe here a method for ex vivo radiolabeling of T cells, a reliable and robust technique for PET imaging of the kinetics of T cell biodistribution from the time of administration to subsequent localization in targeted tumors and other tissues of the body. This noninvasive technique can provide valuable information to monitor and identify the potential efficacy of adoptive cell therapies.
Key wordsT cell Immunotherapy Adoptive cell therapy PET Human nuclear reporter gene Reporter probe Ex vivo radiolabeling Tumor microenvironment
This work was supported by NIH P50 CA86438, R01 CA163980 and R01 CA161138 grants, Mr. William H. Goodwin and Mrs. Alice Goodwin and the Commonwealth Foundation for Cancer Research and The Experimental Therapeutics Center of Memorial Sloan Kettering Cancer Center, NIH Small-Animal Imaging Research Program (SAIRP), NIH Shared Instrumentation Grant No 1 S10 RR020892-01, NIH Shared Instrumentation Grant No 1 S10 RR028889-01, and NIH Center Grants P30 CA08748 and P30 CA08748.
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