title: Longitudinal, noninvasive imaging of T-cell effector function and proliferation in living subjects.
abstract: Adoptive immunotherapy is evolving to assume an increasing role in treating cancer. Most imaging studies in adoptive immunotherapy to date have focused primarily on locating tumor-specific T cells rather than understanding their effector functions. In this study, we report the development of a noninvasive imaging strategy to monitor T-cell activation in living subjects by linking a reporter gene to the Granzyme B promoter (pGB), whose transcriptional activity is known to increase during T-cell activation. Because pGB is relatively weak and does not lead to sufficient reporter gene expression for noninvasive imaging, we specifically employed 2 signal amplification strategies, namely the Two Step Transcription Amplification (TSTA) strategy and the cytomegalovirus enhancer (CMVe) strategy, to maximize firefly luciferase reporter gene expression. Although both amplification strategies were capable of increasing pGB activity in activated primary murine splenocytes, only the level of bioluminescence activity achieved with the CMVe strategy was adequate for noninvasive imaging in mice. Using T cells transduced with a reporter vector containing the hybrid pGB-CMVe promoter, we were able to optically image T-cell effector function longitudinally in response to tumor antigens in living mice. This methodology has the potential to accelerate the study of adoptive immunotherapy in preclinical cancer models.
authors.affiliation: Molecular Imaging Program at Stanford, Stanford University, Stanford, California 94305, USA.
authors.forename: Manishkumar R
authors.initials: MR
authors.lastname: Patel
authors.forename: Ya-Fang
authors.initials: YF
authors.lastname: Chang
authors.forename: Ian Y
authors.initials: IY
authors.lastname: Chen
authors.forename: Michael H
authors.initials: MH
authors.lastname: Bachmann
authors.forename: Xinrui
authors.initials: X
authors.lastname: Yan
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Contag
authors.forename: Sanjiv S
authors.initials: SS
authors.lastname: Gambhir
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004742:Enhancer Elements, Genetic; D017930:Genes, Reporter; D053804:Granzymes / Q000096:biosynthesis / Q000235:genetics; D008163:Luminescent Measurements; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic; D013601:T-Lymphocytes / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D013945:Thymoma / Q000235:genetics / Q000276:immunology*; D013953:Thymus Neoplasms / Q000235:genetics / Q000276:immunology*; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D053804:Granzymes