A Functional Chemiluminescent Probe for in Vivo Imaging of Natural Killer Cell Activity Against Tumours

Abstract

Natural killer (NK) cells are immune cells that can kill certain types of cancer cells. Adoptive transfer of NK cells represents a promising immunotherapy for malignant tumours; however, there is a lack of methods to validate anti‐tumour activity of NK cells in vivo. Herein, we report a new chemiluminescent probe to image in situ the granzyme B‐mediated killing activity of NK cells against cancer cells. We have optimised a granzyme B‐specific construct using an activatable phenoxydioxetane reporter so that enzymatic cleavage of the probe results in bright chemiluminescence. The probe shows high selectivity for active granzyme B over other proteases and higher signal‐to‐noise ratios than commercial fluorophores. Finally, we demonstrate that the probe can detect NK cell activity in mouse models, being the first chemiluminescent probe for in vivo imaging of NK cell activity in live tumours.

Endogenous Stimuli‐Activatable Nanomedicine for Immune Theranostics for Cancer

“…[ 146 ] Over the past decades, various molecular imaging modalities have been employed for tracking the tumor biomarkers (e.g., inflammatory signals, cytokines, immune cells, or immune checkpoints) and boosting immune theranostic of cancer. [ 147 ] Among these advanced techniques, NIR fluorescence imaging has been extensively used in the clinical setting due to its advantages of low autofluorescence, deep tissue penetration, and minimal light scattering. [ 148 ] However, most NIR fluorescence probes were designed for actively targeting the immune‐related proteins.…”

Activatable Chemiluminescent Molecular Probes for Bioimaging and Biosensing

“…Based on the above basic research, the researchers designed and synthesized various chemiluminescence probes based on Schaap's dioxetane for biological application (Fig- ure 6), such as sensing enzymes (β-galactosidase (68-72), [82,91,33] cathepsin B (73), NAD(P)H: quinone oxidoreductase-1 (74), alkaline phosphatase (75), [92,93,35] prostate specific antigen (76), [94] granzyme B (77), [95] H 2 O 2 (78, 79, 80), [91,35,96] azanone (81), [97] formaldehyde (82, 83), [37] H 2 S (84), [34] GSH (85), [35] F À (86), [36] ONOO À (87) [98] and 1 O 2 (88). [99] The corresponding chemiluminescence properties are presented in the Table 2.…”

Monitoring Immunotherapy With Optical Molecular Imaging

“…Similar to the assessment of immune response by imaging CD8 + and CD4 + T cells, imaging of granzyme B released by NK cells in situ can also effectively detect the tumor-killing activity of NK cells. [16] Upon recognition of target tumor cells, NK cells release cytolytic granzymes into target cells and induce apoptosis. [31a] Similar to the assessment of immune response by imaging CD8 + and CD4 + T cells, imaging of granzyme B released by NK cells in situ can also effectively detect the tumor-killing activity of NK cells.…”

“…Therefore, a noninvasive probe for imaging granzyme B is necessary to evaluate the process of NK cells killing cancer cells. Scott et al [16] optimized a granzyme B-specific construct using an activatable phenoxydioxetane chemiluminescent probe in a preclinical mouse model of NK cells adoptive transfer and quantitatively [14]. Copyright: 2020, American Chemical Society Publishing Group, Ref.…”