Metabolic radiolabeling and in vivo PET imaging of cytotoxic T lymphocytes to guide combination adoptive cell transfer cancer therapy

Abstract

Background Adoptive T cell transfer-based immunotherapy yields unsatisfactory results in the treatment of solid tumors, partially owing to limited tumor infiltration and the immunosuppressive microenvironment in solid tumors. Therefore, strategies for the noninvasive tracking of adoptive T cells are critical for monitoring tumor infiltration and for guiding the development of novel combination therapies. Methods We developed a radiolabeling method for cytotoxic T lymphocytes (CTLs) that comprises metabolically labeling the cell surface glycans with azidosugars and then covalently conjugating them with 64Cu-1,4,7-triazacyclononanetriacetic acid-dibenzo-cyclooctyne (64Cu-NOTA-DBCO) using bioorthogonal chemistry. 64Cu-labeled control-CTLs and ovalbumin-specific CTLs (OVA-CTLs) were tracked using positron emission tomography (PET) in B16-OVA tumor-bearing mice. We also investigated the effects of focal adhesion kinase (FAK) inhibition on the antitumor efficacy of OVA-CTLs using a poly(lactic-co-glycolic) acid (PLGA)-encapsulated nanodrug (PLGA-FAKi). Results CTLs can be stably radiolabeled with 64Cu with a minimal effect on cell viability. PET imaging of 64Cu-OVA-CTLs enables noninvasive mapping of their in vivo behavior. Moreover, 64Cu-OVA-CTLs PET imaging revealed that PLGA-FAKi induced a significant increase in OVA-CTL infiltration into tumors, suggesting the potential for a combined therapy comprising OVA-CTLs and PLGA-FAKi. Further combination therapy studies confirmed that the PLGA-FAKi nanodrug markedly improved the antitumor effects of adoptive OVA-CTLs transfer by multiple mechanisms. Conclusion These findings demonstrated that metabolic radiolabeling followed by PET imaging can be used to sensitively profile the early-stage migration and tumor-targeting efficiency of adoptive T cells in vivo. This strategy presents opportunities for predicting the efficacy of cell-based adoptive therapies and for guiding combination regimens. Graphic Abstract

Direct Cell Radiolabeling for in Vivo Cell Tracking with PET and SPECT Imaging

“…The authors used this methodology to incorporate azide-functionalized oligosaccharides on the surface of CTLs by first pretreating them with the monosaccharide Ac 4 ManNAz for 24 h to generate azide groups, and then labeling with radioactive biorthogonal click component [ 64 Cu]­Cu-NOTA-DBCO (Figure ). The cell labeling was shown to be specific for the glycoengineered cells with approximately three times higher LE for CTLs treated with the monosaccharide than for untreated cells. Additionally, the cellular retention of the bound [ 64 Cu]­Cu-NOTA-DBCO was high, with <20% efflux of 64 Cu after 48 h. While this method may be unnecessarily complicated for direct cell labeling and tracking, glycoengineering could be used as a basis for indirect cell labeling: azide-functionalized cells could potentially be imaged longitudinally using bioorthogonal tracers.…”

“…Figure 12. Schematic overview of metabolic glycoengineering approached used by Lu et al168 The OVA-CTLs were metabolically modified with azide-linked oligosaccharides which allowed radiolabeling of the cells with the [64 Cu]Cu-NOTA-DBCO click component.…”

Emerging Biomaterials Imaging Antitumor Immune Response

“…First, the CTL surface was modified with azide, and then 64 Cu‐1,4,7‐triazacyclononanetriacetic acid‐dibenzo‐cyclooctyne ( 64 Cu‐NOTA‐DBCO) was covalently bound to the surface of CTL ( Figure a). [ 110 ] The obtained 64 Cu‐NOTA‐DBCO molecule showed more than 80% purity after 24 h in phosphate‐buffered saline (PBS) and fetal bovine serum, with good stability and almost no toxicity to CTL. Moreover, PET imaging can be used to analyze the early migration of adoptive T cells in vivo and tumor targeting efficiency.…”

“…Reproduced with permission. [ 110 ] Copyright 2021, Springer Nature. d,e) Schematic illustration of bioorthogonal labeled CTLs (Cy5.5–CTLs) and monitoring Cy5.5–CTLs by using NIRF.…”

“…b) PET images, c) quantification of tumor uptake and tumor-to-muscle ratios of64 Cu-OVA-CTLs. Reproduced with permission [110]. Copyright 2021, Springer Nature.…”