SUMMARY The high expression across multiple tumor types and restricted expression in normal tissues make B7-H3 an attractive target for immunotherapy. We generated chimeric antigen receptor (CAR) T cells targeting B7-H3 (B7-H3.CAR-Ts) and found that B7-H3.CAR-Ts controlled the growth of pancreatic ductal adenocarcinoma, ovarian cancer and neuroblastoma in vitro and in orthotopic and metastatic xenograft mouse models, which included patient-derived xenograft. We also found that 4–1BB co-stimulation promotes lower PD-1 expression in B7-H3.CAR-Ts, and superior antitumor activity when targeting tumor cells that constitutively expressed PD-L1. We took advantage of the cross-reactivity of the B7-H3.CAR with murine B7-H3, and found that B7-H3.CAR-Ts significantly controlled tumor growth in a syngeneic tumor model without evident toxicity. These findings support the clinical development of B7-H3.CAR-Ts.

Chimeric antigen receptor (CAR)-redirected T lymphocytes (CAR T cells) show modest therapeutic efficacy in solid tumors. The desmoplastic structure of the tumor and the immunosuppressive tumor microenvironment usually account for the reduced efficacy of CAR T cells in solid tumors. Mild hyperthermia of the tumor reduces its compact structure and interstitial fluid pressure (IFP), increases blood perfusion, releases antigens and promotes the recruitment of endogenous immune cells. Therefore, the combination of mild hyperthermia with the adoptive transfer of CAR T cells could potentially increase the therapeutic index of these cells in solid tumors. We found that the chondroitin sulfate proteoglycan-4 (CSPG4)-specific CAR T cells infused in Nod scid gamma (NSG) mice engrafted with the human melanoma WM115 cell line had superior antitumor activity after photothermal ablation of the tumor. Our findings suggest that photothermal therapy facilitates the accumulation and effector function of CAR T cells within the solid tumor.

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Highlights d LCK promotes basal CAR-CD3z phosphorylation in the synapse of CAR.CD28z d THEMIS-SHP1 counteracts the effect of LCK in the synapse of CAR.4-1BBz d Engineering LCK kinase tunes up the antitumor activity of CAR.4-1BBz-T cells d Engineering druggable SHP1 phosphatase tunes down the function of CAR.