Functional heterogeneity of cytotoxic T cells and tumor resistance to cytotoxic hits limit anti‐tumor activity in vivo

• Published in: The EMBO journal Vol. 40; no. 11; pp. e106658 - n/a
• Main Authors: Khazen, Roxana, Cazaux, Marine, Lemaître, Fabrice, Corre, Beatrice, Garcia, Zacarias, Bousso, Philippe
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.06.2021; Springer Nature B.V; EMBO Press; John Wiley and Sons Inc
• Subjects: Animals; Antigens, CD19 - immunology; Apoptosis; B-Lymphocytes - immunology; Bone imaging; Bone marrow; Calcium; Calcium - metabolism; CAR T cells; CD19 antigen; Cell Membrane - metabolism; Cells, Cultured; CTL; Cytotoxicity; Damage; EMBO03; EMBO19; Genetic code; Heterogeneity; Immunological synapses; Immunological Synapses - immunology; Immunology; Immunotherapy, Adoptive; intravital imaging; lethal hit; Life Sciences; Lymphocytes; Lymphocytes B; Lymphocytes T; Lymphoma; Lymphoma - immunology; Lymphoma - therapy; Membranes; Mice; Mice, Inbred C57BL; Receptors, Chimeric Antigen - immunology; sublethal hit; Synapses; T-Lymphocytes, Cytotoxic - immunology; Target recognition; Tumor cells; Tumor microenvironment; Tumors; CTL; CAR T cells; intravital imaging; sublethal hit; lethal hit; Immunology; sublethal hit Subject Categories Cancer
• DOI: 10.15252/embj.2020106658
• ISSN: 0261-4189; 1460-2075

Cytotoxic T cells (CTLs) can eliminate tumor cells through the delivery of lethal hits, but the actual efficiency of this process in the tumor microenvironment is unclear. Here, we visualized the capacity of single CTLs to attack tumor cells in vitro and in vivo using genetically encoded reporters that monitor cell damage and apoptosis. Using two distinct malignant B‐cell lines, we found that the majority of cytotoxic hits delivered by CTLs in vitro were sublethal despite proper immunological synapse formation, and associated with reversible calcium elevation and membrane damage in the targets. Through intravital imaging in the bone marrow, we established that the majority of CTL interactions with lymphoma B cells were either unproductive or sublethal. Functional heterogeneity of CTLs contributed to diverse outcomes during CTL–tumor contacts in vivo . In the therapeutic settings of anti‐CD19 CAR T cells, the majority of CAR T cell–tumor interactions were also not associated with lethal hit delivery. Thus, differences in CTL lytic potential together with tumor cell resistance to cytotoxic hits represent two important bottlenecks for anti‐tumor responses in vivo . SYNOPSIS The efficiency of CTL or CAR T cell lethal hit delivery in the tumor microenvironment is unclear. Here, intravital imaging and functional reporters were used to quantify the various outcomes of T cell‐tumor contacts, revealing that a minority of interactions resulted in target cell killing. Most CTL‐tumor cell contacts are non‐lethal. Tumor cells often recover from CTL‐induced membrane damage. CTLs or CAR T cells exhibit extensive variability in killing capacities in vivo . Graphical Abstract Intravital imaging of T cell‐tumor contacts reveals variability in the ability of cytotoxic T cells to kill tumor cells and that the majority of interactions are non‐lethal.