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Adrenocortical carcinoma (ACC) is a rare and aggressive malignancy with poor prognosis and limited curative treatment options. While chimeric antigen receptor (CAR) T cells have shown some promise in solid tumors, ACC remains largely unexplored in this context. Here, we used patient-derived xenograft (PDX) models of ACC to identify immunotherapeutic targets and develop novel CAR T-cell strategies.

Target identification and tumor microenvironment (TME) profiling were conducted using publicly available bulk and single-cell RNA sequencing data from patients with ACC samples. Surface proteomic analysis and flow cytometry of PDXs were conducted to validate antigen candidates. CAR T cells were engineered and tested for cytotoxicity in vitro and in vivo and profiled using flow cytometry and cytokine analysis.

We identified ectonucleotide pyrophosphatase/phosphodiesterase family member 3 (ENPP3) as a shared immunotherapy target in 4/7 (57%) ACC PDXs. ENPP3-targeted CAR T-cells eradicated >85% of ENPP3⁺ ACC cells in vitro but showed attenuated efficacy in PDX mouse models. Restrained ENPP3 CAR T-cell activity correlated with immunosuppressive features of the TME, particularly the presence of CD206⁺ tumor-associated macrophages (TAMs). Co-treatment with an agent modulating CD206⁺ TAMs restored CAR T-cell function and improved antitumor responses in ENPP3^high and ENPP3^low PDX models (difference between mean tumor weights -270.1 mg±117.4; p<0.05).

ENPP3 is a novel target for CAR T-cell therapy in ACC. ENPP3 CAR T cells, when combined with CD206 modulation to overcome immune suppression within the TME, have therapeutic efficacy in ACC by mediating robust tumor growth suppression. This combinatorial strategy, which includes CAR T cells alongside therapies that recalibrate immunosuppressive CD206⁺ TAMs, may be a novel approach for improved immunotherapy of solid cancers beyond ACC.