增强 Fas/FasL 信号提升 CAR-T 旁观者杀伤并减轻异质性肿瘤中的抗原逃逸

Antigen (Ag) escape is a frequent mechanism of relapse after CAR-T therapy, even though only 1% of leukemic and 0. 1% of lymphoma cells are Ag at baseline. In this study, we modeled extreme Ag heterogeneity (>20%) to define how Fas/FasL-dependent bystander killing contributes to tumor clearance. Across patient cohorts, Fas expression predicted survival after CD19 CAR-T therapy, particularly in CD19-low disease.

In both murine and human systems, Fas-dependent bystander killing required Ag stimulation and cell contact, operated within a defined therapeutic window, and could eradicate large fractions of Ag tumors in vivo . Pharmacologic potentiation with inhibitor of apoptosis protein antagonists or genetic stabilization of CAR-T membrane-bound FasL enhanced bystander killing but simultaneously induced CD4 T cell fratricide, which was rescued by CAR-T Fas knockout.

Importantly, Fas sensitization also enabled bispecific antibody-redirected T cells to mediate bystander killing in resistant tumors.

Finally, targeting tumor-associated macrophages triggered Fas-dependent clearance of neighboring tumor cells.

These findings establish Fas-mediated bystander killing as a generalizable and therapeutically actionable axis to prevent Ag escape and broaden the scope of targeted T cell therapies.