Phenotypic Models of CAR T-Cell Activation Elucidate the Pivotal Regulatory Role of CAR Downmodulation

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• Adoptive cell immunotherapy using chimeric antigen receptor (CAR) T-cells has shown success in blood cancers but limited efficacy in solid tumors.
• Previous research explored biophysical parameters like affinity, avidity, and antigen density in CAR T-cell activity, revealing complex relationships.

Purpose of the Study:

• To investigate the role of receptor downmodulation in CAR T-cell function and identify strategies to enhance anti-tumor responses.
• To develop and utilize an evolving phenotypic model for CAR T-cell regulation.

Main Methods:

• Developed an evolving phenotypic model to predict CAR T-cell regulation.
• Measured and manipulated receptor downmodulation and intracellular signaling pathways.
• Inhibited actin polymerization and regulatory inhibitory phosphatases to assess effects on CAR T-cell responses.
• Documented trogocytosis in CAR T-cells and its dependence on actin polymerization.

Main Results:

• Receptor downmodulation was identified as a critical factor in CAR T-cell function.
• Inhibiting CAR T-cell receptor downmodulation by blocking actin polymerization significantly increased CAR T-cell anti-tumor responses.
• Inhibition of regulatory inhibitory phosphatases did not enhance CAR T-cell responses.
• Trogocytosis, a cell-cell interaction mechanism, was observed in CAR T-cells and linked to actin polymerization.

Conclusions:

• CAR T-cell function is significantly influenced by receptor downmodulation, a process dependent on actin polymerization.
• Targeting actin polymerization to inhibit receptor downmodulation represents a promising strategy to enhance CAR T-cell efficacy in solid tumors.
• This study provides insights into CAR T-cell regulation, potentially guiding the rational design of improved adoptive cell therapies.