CAR-T cell therapy senses ‘faint’ targets to clear solid tumours, PgII

Key Highlights:

• CAR-T cell therapy works well in blood cancers, but faces difficulty in solid tumours due to antigen heterogeneity
• Tumour cells previously thought “undetectable” actually express very low levels of CD70 protein
• This low expression is not absence, but a hidden signal missed by conventional CAR-T cells
• Scientists developed a HIT (HLA-independent T-cell) receptor to detect these faint signals
• HIT receptor links detection directly to the natural activation pathway of T-cells
• In experimental models, HIT-based T-cells showed complete and long-lasting tumour removal

Detailed Insights:

• Antigen heterogeneity in solid tumors allows some cells to evade detection by CAR-T cells, leading to cancer regrowth.
• The enzyme EZH2 suppresses the gene for CD70, reducing its production and making cells undetectable to current immune therapies.
• The HIT receptor bypasses the HLA system, enabling it to detect antigens at much lower densities than synthetic CAR-T cells.
• Safety concerns about the HIT receptor reacting to normal cells were addressed by analyzing a single-cell atlas, which showed limited CD70 activity in vital organs.
• Drug-tolerant persisters, which survive targeted therapies, can be addressed by the HIT receptor's ability to uncover and eliminate hidden cells.

Key Concepts Involved:

• CAR-T Cell Therapy: Immunotherapy using engineered T-cells to identify and destroy cancer cells
• Antigen Heterogeneity: Variation in protein expression across tumour cells, enabling immune evasion
• HLA System: Cell-surface protein system that helps immune cells recognise targets
• Pseudo-heterogeneity: Apparent absence of antigen due to extremely low expression levels

CAR-T Cell Therapy