Chelerythrine and chelidonine synergistically target the adenosine pathway to improve anti-PD-L1 immunotherapy efficacy in lung cancer.

BACKGROUND: Despite the success of immune checkpoint blockade in advanced cancer, non-redundant immunosuppressive mechanisms within the tumor microenvironment (TME) limit its effectiveness in many patients. Extracellular adenosine (eADO) signaling is a major contributor to immunosuppression, and inhibitors of eADO production or signaling have entered clinical trials as monotherapies or in combination with anti-PD-L1 therapy. PURPOSE: We aimed to identify potent compounds from Chelidonium majus L. (C. majus) that target eADO production or signaling pathway and thereby improve the efficacy of anti-PD-L1 immunotherapy in lung cancer. METHODS: A systems pharmacology platform was used to screen compounds from C. majus for potential antitumor activity. Synergistic interactions among the candidate compounds were evaluated using the Chou-Talalay method. The ability of chelerythrine and chelidonine (CC) to enhance anti-PD-L1 efficacy was evaluated in a syngeneic Lewis lung carcinoma (LLC) mouse model. ELISA, quantitative real-time PCR and Western blotting were used to assess eADO production and CD39/CD73-axis signaling in the CC-treated TME. Flow cytometry, Transwell co-culture assays and ELISA were used to evaluate immunomodulatory effects of CC on CD8+ T cells. RESULTS: We investigated whether chelerythrine and chelidonine combined at a 1:1 concentration ratio (CC), two alkaloids derived from C. majus, inhibit eADO production and signaling through the CD39/CD73 axis and thereby enhance CD8+ T-cell responses in LLC-bearing mice. Computational modeling predicted favorable antitumor properties for CC, which were subsequently validated in vitro and in vivo. Mechanistically, CC significantly reduced CD39 and CD73 expression and alleviated eADO-mediated immunosuppression in the TME. CC also enhanced antitumor CD8+ T-cell immunity in LLC-bearing mice by increasing intratumoral infiltration and cytotoxic function. Furthermore, CC improved the therapeutic efficacy of anti-PD-L1 treatment in established tumors. CONCLUSIONS: This study demonstrates that CC synergistically targets the eADO pathway and improves the efficacy of anti-PD-L1 immunotherapy through the CD39/CD73/A2AR axis in lung cancer model. These findings provide a scientific rationale for developing adenosine-targeted combination strategies with immune checkpoint blockade (ICB).