Bursting Tumor Bubbles to Improve CAR T-cell Therapy

Area of Science:

• Immunotherapy
• Extracellular Vesicles
• Solid Tumor Oncology

Background:

• Chimeric antigen receptor (CAR) T-cell therapy shows success in B-cell cancers but limited efficacy in solid tumors.
• The mechanisms limiting CAR T-cell activity in solid tumors remain incompletely understood.

Purpose of the Study:

• To investigate the role of tumor-derived small extracellular vesicles (sEVs) in suppressing CAR T-cell activity in solid tumors.
• To explore strategies targeting sEV secretion for enhancing CAR T-cell therapy.

Main Methods:

• Analysis of CAR target antigens and PD-L1 expression in tumor-derived sEVs.
• In vivo studies assessing CAR T-cell interactions with sEVs and the impact of PD-L1 blockade.
• Evaluation of genetic and pharmacologic inhibition of sEV secretion on CAR T-cell efficacy.

Main Results:

• Tumor-derived sEVs were found to contain CAR target antigens (e.g., mesothelin) and interact with CAR T cells.
• PD-L1 expression on sEVs increased post-CAR T-cell infusion, leading to PD-L1-dependent suppression of CAR T cells.
• Inhibition of sEV secretion significantly improved CAR T-cell accumulation, function, and antitumor activity in vivo.

Conclusions:

• Tumor-derived sEVs represent a significant mechanism of CAR T-cell suppression in solid tumors.
• Targeting sEV secretion presents a promising therapeutic approach to overcome CAR T-cell resistance in solid tumors.