MUC1-targeted CAR-T cell secreted anti-PD-1 IgG antibody enhances antitumor activity in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a highly aggressive malignancy with poor prognosis and limited therapeutic options. Gene expression analysis of patient samples and flow cytometry of CCA cell lines demonstrated significant upregulation of MUC1 and PD-L1, supporting their relevance as immunotherapeutic targets. To address immune suppression mediated by PD-1/PD-L1 signaling, we developed MUC1-specific CAR-T cells engineered to secrete a full-length anti-PD-1 immunoglobulin (MUC1.PD1 CAR-T cells). The MUC1.PD1 CAR-T cells exhibited high transduction efficiency and showed memory phenotypes comparable to conventional MUC1 CAR-T cells. Both constructs mediated antigen-specific cytotoxicity against MUC1⁺PD-L1⁺ CCA cells in vitro. Under chronic antigen stimulation, MUC1.PD1 CAR-T cells displayed reduced detectable PD-1 expression and maintained superior proliferative capacity compared with conventional MUC1 CAR-T cells. In vivo, in a NOD/SCID xenograft model of CCA, conventional MUC1 CAR-T cells failed to control tumor growth, whereas MUC1.PD1 CAR-T cells significantly suppressed tumor progression. These findings demonstrate that the secretion of full-length anti-PD-1 immunoglobulin enhances CAR-T cell function and anti-tumor activity in the context of CCA.