Engineered PD-L1 co-expression in PD-1 knockout and MAGE-C2-targeting TCR-T cells augments the cytotoxic efficacy toward target cancer cells

Expression of the PD-1 protein by tumor cells is relatively common and has been shown to exert proliferation-inhibitory effects across various tumor types, including T-cell malignancies, non-small cell lung cancer, and colon cancer. However, harnessing this tumor suppressor pathway is challenging because PD-1 activation by PD-L1 also suppresses normal T-cell function. We hypothesized that cancer antigen-specific TCR-T cells engineered to express PD-L1 could selectively activate the PD-1 pathway in tumor cells while simultaneously preventing self-inhibition by knocking out intrinsic PD-1 expression in TCR-T cells. To test this hypothesis, we co-expressed a MAGE-C2-specific recombinant TCR and the PD-L1-encoding CD274 gene in normal human T cells in which the PDCD1 gene was knocked out. These engineered TCR-T cells targeted MAGE-C2-expressing malignant cells, activating PD-1 signaling to suppress tumor proliferation while maintaining suppressed PD-1 signaling in the TCR-T cells themselves. To evaluate the tumor-suppressive potential of this approach, we compared the efficacy of PDL1-MC2-TCR-T^PD1⁻ cells against subtypes lacking PD-L1 expression, PD-1 knockout, or both. Our findings demonstrated that this TCR-T model exhibited significantly enhanced cytotoxic efficacy compared to other subtypes in vitro, ex vivo, and in vivo. These results suggest that the targeted activation of intrinsic PD-1 signaling in T-cell malignancies inhibits tumor proliferation and, when combined with PD-1 inhibition in TCR-T cells, synergistically enhances their cancer-suppressing efficacy. This study provides a foundation for novel cancer treatment strategies.