FcεRγI promotes canine CD8 chimeric antigen receptor T cell cytotoxicity through a Syk-NF-κB axis

Area of Science:

• Comparative oncology
• Immunotherapy
• Cellular immunology

Background:

• Chimeric antigen receptor T cell (CART) therapy shows promise in comparative oncology but its mechanisms in canines are not fully understood.
• Previous canine CART trials using canine 4-1BB-CD3ζ (cBBζ) domains showed limited efficacy, with lymphoma outgrowth and lack of B cell depletion.

Purpose of the Study:

• To investigate the therapeutic potential of canine CARTs incorporating human 4-1BB-CD3ζ (hBBζ) domains.
• To elucidate the cellular mechanisms underlying enhanced CART function mediated by hBBζ domains.

Main Methods:

• Comparative analysis of canine CARTs with cBBζ versus hBBζ domains in vitro and in a canine B cell leukemia xenograft model.
• Transcriptional profiling of CART subsets.
• CRISPR-mediated gene deletion and pharmacologic inhibition to investigate signaling pathways.

Main Results:

• Canine CARTs with hBBζ domains demonstrated superior cytolysis and CD8 T cell expansion compared to cBBζ-CARTs.
• hBBζ-CARTs exhibited upregulation of FCER1G and innate-like immune genes.
• Syk-NF-κB signaling pathway activation was identified as crucial for FcεRγI-mediated enhancement of hBBζ-CART cytotoxicity, leading to increased granzyme B and IFN-γ/TNF-α production.

Conclusions:

• Canine CARTs incorporating hBBζ domains represent a potent therapeutic subset with enhanced cytotoxic function, mediated by FcεRγI and Syk-NF-κB signaling.
• These findings offer a potential strategy to improve CART therapy efficacy in both canine and human oncology.