Immune Cell-Mediated Killing
The differences in clinical efficacy of immunotherapy between non-solid and solid tumours are multifactorial. These include physical restrictions, such as the limited accessibility of cancer cells, intrinsic properties of the tumor cells that influence their immunogenicity and sensitivity to immune effectors, and the presence of inhibitory metabolic processes and soluble inhibitors in the parenchyma surrounding cancer cells, all of which can adversely affect T cell immunotherapy efficacy.
Preclinical testing to evaluate the efficacy of the different modifications introduced in engineered T cells for cancer immunotherapy still relies on expensive animal models that are not fully able to recapitulate human pathology; additionally, tests in animal models lack the flexibility to control individual parameters in distinct anatomical locations. In vitro testing offers an alternative, but 2D in vitro models cannot mimic the spatiotemporal dynamics encountered by T cells targeting cancer cells within solid parenchyma. In addition, such testing methodologies have neglected the obvious 3D morphology of solid tumors and the tumor cell clusters necessary for metastasis formation.
T Cells Single Cells
Dispersed GFP-expressing HepG2-Env liver cancer cells (green) in 3D collagen matrix were targeted by engineered T-cells (blue) and killed specifically (red, labelled with DRAQ7). Killing efficiency can be calculated by dividing the number of live cancer cells at the endpoint by the number of live cancer cells at time 0.
T Cells Organiods
HepG2-Env aggregates embedded in a 3D collagen matrix and exposed to engineered T-cells resulted in a quantifiable increase in killed cells (red). Quantifying live & dead cells in cancer aggregates is usually less accurate as the cancer cells clump together. Therefore, the % of cell death is estimated based on the volumes of DRAQ7-positive cells and GFP-positive cells. The killing efficiency of T cells can be obtained by comparing the % of cell death before the addition of T cells with that after 15 h incubation. The greater the difference in % of cell death between the two time points, the more potent the T cells.
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