A Critical Role for Fas-Mediated Off-Target Tumor Killing in T-Cell Immunotherapy
Published OnlineFirst December 17, 2020; DOI: 10.1158/2159-8290.CD-20-0756 RESEARCH BRIEF A Critical Role for Fas-Mediated Off-Target Tumor Killing in T-cell Immunotherapy Ranjan Upadhyay1,2,3, Jonathan A. Boiarsky1,2,3, Gvantsa Pantsulaia1,2,3, Judit Svensson-Arvelund1,2,3, Matthew J. Lin1,2,3, Aleksandra Wroblewska2,3,4, Sherry Bhalla3,4, Nathalie Scholler5, Adrian Bot5, John M. Rossi5, Norah Sadek1,2,3, Samir Parekh1,2,3, Alessandro Lagana4, Alessia Baccarini2,3,4, Miriam Merad2,3,6, Brian D. Brown2,3,4, and Joshua D. Brody1,2,3 ABSTRACT T cell–based therapies have induced cancer remissions, though most tumors ulti- mately progress, reflecting inherent or acquired resistance including antigen Bianca Dunn by Illustration escape. Better understanding of how T cells eliminate tumors will help decipher resistance mecha- nisms. We used a CRISPR/Cas9 screen and identified a necessary role for Fas–FasL in antigen-specific T-cell killing. We also found that Fas–FasL mediated off-target “bystander” killing of antigen-negative tumor cells. This localized bystander cytotoxicity enhanced clearance of antigen-heterogeneous tumors in vivo, a finding that has not been shown previously. Fas-mediated on-target and bystander killing was reproduced in chimeric antigen receptor (CAR-T) and bispecific antibody T-cell models and was augmented by inhibiting regulators of Fas signaling. Tumoral FAS expression alone predicted survival of CAR-T–treated patients in a large clinical trial (NCT02348216). These data suggest strate- gies to prevent immune escape by targeting both the antigen expression of most tumor cells and the geography of antigen-loss variants.
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