Rab5 improves CAR T cell efficacy via reducing fratricide and maintaining surface CAR levels.

Area of Science:

• Immunology
• Cell Biology
• Cancer Therapy

Background:

• Chimeric antigen receptor (CAR) T cell (CART) therapy shows promise but faces challenges like tumor-induced dysfunction.
• Tumor exposure leads to decreased CAR T cell endocytic activity via Rab5 downregulation.
• This dysfunction is linked to trogocytosis, a process exacerbating CAR T cell failure.

Purpose of the Study:

• To investigate the role of Rab5 in CAR T cell endocytosis and function.
• To determine if enhancing Rab5 expression can overcome tumor-induced CAR T cell dysfunction.
• To evaluate the therapeutic potential of Rab5-engineered CAR T cells in preclinical models.

Main Methods:

• Assessed CAR T cell endocytic activity and Rab5 expression after tumor exposure.
• Utilized genetic engineering to achieve constitutive Rab5 expression in CAR T cells.
• Evaluated CAR T cell fratricide and antitumor activity in vitro and in vivo models (BCMA-CARTs and mesothelin-specific CARTs).

Main Results:

• Continuous tumor exposure downregulated Rab5, impairing CAR T cell endocytosis and promoting fratricide.
• Constitutive Rab5 expression reduced fratricide by limiting trogocytosis and enhancing CAR recycling.
• Rab5-expressing CAR T cells demonstrated superior antitumor efficacy in both hematologic and solid tumor models.

Conclusions:

• Rab5 plays a critical role in maintaining CAR T cell function by regulating endocytosis and trogocytosis.
• Engineering CAR T cells with enhanced Rab5 expression represents a promising strategy to improve therapeutic efficacy.
• This approach could overcome key mechanisms of resistance in CAR T cell therapy.