Non-invasive cell-tracking methods for adoptive T cell therapies.

• In vivo tracking of engineered T cells provides important spatiotemporal information. • Direct cell labeling with radionuclides or MRI-contrast agents can be envisioned. • Indirect cell labeling with reporter genes allows prolonged T cell-tracking. • Both labeling approaches could benefit from improved intracellular delivery methods. Adoptive T cell therapies (ACT) have demonstrated groundbreaking results in blood cancers and melanoma. Nevertheless, their significant cost, the occurrence of severe adverse events, and their poor performance in solid tumors are important hurdles hampering more widespread applicability. In vivo cell-tracking allows instantaneous and non-invasive monitoring of the distribution, tumor homing, persistence, and redistribution to other organs of infused T cells in patients. Furthermore, cell-tracking could aid in the clinical management of patients, allowing the detection of non-responders or severe adverse events at an early stage. This review provides a concise overview of the main principles and potential of cell-tracking, followed by a discussion of the clinically relevant labeling strategies and their application in ACT. [ABSTRACT FROM AUTHOR]