SMAD7 expression in CAR-T cells improves persistence and safety for solid tumors

Despite the tremendous progress of chimeric antigen receptor T(CAR-T)cell therapy in hematological malignancies,their application in solid tumors has been limited largely due to T-cell exhaustion in the tumor microenvironment(TME)and systemic toxicity caused by excessive cytokine release.As a key regulator of the immunosuppressive TME,TGF-βpromotes cytokine synthesis via the NF-κB pathway.Here,we coexpressed SMAD7,a suppressor of TGF-βsignaling,with a HER2-targeted CAR in engineered T cells.These novel CAR-T cells displayed high cytolytic efficacy and were resistant to TGF-β-triggered exhaustion,which enabled sustained tumoricidal capacity after continuous antigen exposure.Moreover,SMAD7 substantially reduced the production of inflammatory cytokines by antigen-primed CAR-T cells.Mechanistically,SMAD7 downregulated TGF-βreceptor I and abrogated the interplay between the TGF-βand NF-κB pathways in CAR-T cells.As a result,these CAR-T cells persistently inhibited tumor growth and promoted the survival of tumor-challenged mice regardless of the hostile tumor microenvironment caused by a high concentration of TGF-β.SMAD7 coexpression also enhanced CAR-T-cell infiltration and persistent activation in patient-derived tumor organoids.Therefore,our study demonstrated the feasibility of SMAD7 coexpression as a novel approach to improve the efficacy and safety of CAR-T-cell therapy for solid tumors.