Iodine-124 Based Dual Positron Emission Tomography and Fluorescent Labeling Reagents for In Vivo Cell Tracking.

Truc Thuy Pham,Fangfang Sun,Ran Yan,John Maher,Zhi Lu,Christopher Davis,Chun Li

doi:10.1021/acs.bioconjchem.9b00799

Abstract

Understanding the in vivo behavior of experimental therapeutic cells is fundamental to their successful development and clinical translation. Iodine-124 has the longest half-life (4.2 days) among the clinically used positron emitters. Consequently, this isotope offers the longest possible tracking time for directly labeled cells using positron emission tomography (PET). Herein, we have radiosynthesized and evaluated two iodine-124/fluorescein-based dual PET and fluorescent labeling reagents, namely 124I-FIT-Mal and 124I-FIT-(PhS)2Mal for cell surface thiol bioconjugation. 124I-FIT-(PhS)2Mal labeled cells significantly more effectively than 124I-FIT-Mal. It conjugated to various cell lines in 22%–62% labeling efficiencies with prolonged iodine-124 retention. 124I-FIT-(PhS)2Mal mainly conjugated on the cell membrane, which was confirmed by high-resolution fluorescence imaging. The migration of 124I-FIT-(PhS)2Mal labeled Jurkat cells was visualized in NSG mice with excellent target-to-background contrast using PET/CT over 7 days. These data demonstrate that 124I-FIT-(PhS)2Mal can dynamically track cell migration in vivo using PET/CT over a clinically relevant time frame.

Highlights

Emerging as the fourth pillar of healthcare, cell-based therapies have shown great promise in cancer treatment,1 stem cell regenerative medicine,2 and immune tolerance in organ transplantation.3 For example, adoptive transfer of chimeric antigen receptor (CAR)-engineered T-cells is a novel immunotherapy that utilizes the patient’s own immune system to treat cancer.4 One fundamental challenge in both medical research and clinical applications of cell therapies is to understand the in vivo behavior of the infused cells
Azidoethan-1-amine to generate the 5-[3-(2-azidoethyl)thioureido]-fluorescein in 82% yield
FIT-(PhS)2Mal [2] labeled Jurkat cells was achieved with Positron emission tomography (PET)/CT imaging over 7 days with excellent target-tobackground contrast

Summary

Introduction

Emerging as the fourth pillar of healthcare, cell-based therapies have shown great promise in cancer treatment, stem cell regenerative medicine, and immune tolerance in organ transplantation. For example, adoptive transfer of chimeric antigen receptor (CAR)-engineered T-cells is a novel immunotherapy that utilizes the patient’s own immune system to treat cancer. One fundamental challenge in both medical research and clinical applications of cell therapies is to understand the in vivo behavior of the infused cells. To detect the initial distribution and migration of the infused cells, various direct cell labeling methods have been developed by which the therapeutic cells are labeled with a contrast reagent in vitro. An 89Zrdesferrioxamine-isothiocyanate bioconjugation reagent was reported to label cells through the amine groups in cell surface proteins, allowing the assessment of the distribution of the labeled cells in vivo for days.. An 89Zrdesferrioxamine-isothiocyanate bioconjugation reagent was reported to label cells through the amine groups in cell surface proteins, allowing the assessment of the distribution of the labeled cells in vivo for days.14 When applying both of the above 89Zr based cell tracking methods to monitor the experimental therapeutic cells in preclinical settings, the 89Zr leaks gradually from the labeled cells in vivo and deposits in bones, complicating the interpretation of PET images. An 89Zrdesferrioxamine-isothiocyanate bioconjugation reagent was reported to label cells through the amine groups in cell surface proteins, allowing the assessment of the distribution of the labeled cells in vivo for days. when applying both of the above 89Zr based cell tracking methods to monitor the experimental therapeutic cells in preclinical settings, the 89Zr leaks gradually from the labeled cells in vivo and deposits in bones, complicating the interpretation of PET images.

Results

Discussion

Conclusion