NRCAM variant defined by microexon skipping is a targetable cell surface proteoform in high-grade gliomas

Area of Science:

• Neuro-oncology
• Molecular Biology
• Immunotherapy

Background:

• Pediatric high-grade glioma (pHGG) lacks specific surface antigens for targeted therapies.
• Existing chimeric antigen receptor (CAR)-T cell targets can cause off-tumor toxicities due to shared expression in normal tissues.

Purpose of the Study:

• To identify novel, tumor-specific targets for pHGG immunotherapy.
• To investigate alternatively spliced cell adhesion molecules as potential therapeutic targets.

Main Methods:

• Comparative analysis of splicing patterns in pHGG and normal brain samples.
• RNA sequencing (RNA-seq) to identify microexon skipping events.
• Development of a monoclonal antibody against a specific NRCAM proteoform.
• Assessment of antibody-mediated T-cell killing of pHGG cells.

Main Results:

• Microexon skipping, particularly in L1-IgCAM family members like NRCAM, is a pervasive alteration in pHGG.
• A specific NRCAM proteoform (Δex5Δex19) is crucial for pHGG cell migration, invasion, and tumor growth.
• A novel antibody targeting Δex5Δex19 NRCAM facilitates T-cell mediated killing of pHGG cells.

Conclusions:

• pHGG-specific alternatively spliced NRCAM proteoforms are promising targets for selective immunotherapy.
• This approach may overcome on-target/off-tumor toxicities associated with current CAR-T cell therapies.