Umbilical cord blood-derived cytotoxic T lymphocytes target melanoma via HLA-A2-restricted tumour antigens.

BACKGROUND: Melanoma is recognized as a highly malignant cancer with a generally poor prognosis, underscoring the critical need for effective therapeutic strategies. Adoptive cell therapy has emerged as a promising modality to improve treatment outcomes in melanoma. For endogenous cell therapy (ECT), peripheral blood (PB) has traditionally served as the primary cell source. However, the potential of umbilical cord blood (UCB) as an alternative source for ECT remains unclear. Furthermore, the repertoire of TCRs remains limited. These deficiencies impede the optimization and broader application of ECT for melanoma, highlighting the necessity for focused investigations to resolve these issues. METHODS: To evaluate the effects of HLA-A2 restricted antigen-specific CD8⁺ T cells on melanoma cells, the cytotoxic activity of CD8⁺ T cells derived from UCB and PB were conducted in vivo and in vitro assays. Single-cell RNA sequencing combined with TCR V(D)J sequencing was employed to characterize cellular composition and quantify the frequencies of specific TCR clonotypes. The generation probability and peripheral occurrence probability of antigen-specific CD8⁺ TCR sequences from UCB and PB were computed using the Simple Olga Sonia algorithm. Finally, molecular docking simulations were conducted to predict the binding affinity between isolated TCRs and pMHC. RESULTS: No significant differences were observed in the cytotoxic effects mediated by antigen-specific CD8⁺ T cells derived from UCB versus PB. Phenotypic analysis revealed that PB-derived antigen-specific CD8⁺ T cells were predominantly effector and proliferating cells, whereas those from UCB consisted largely of memory cells. TCR sequencing identified a greater diversity of antigen-specific TCR clonotypes in PB, meanwhile UCB-derived TCRs exhibited strong pMHC binding. Molecular docking simulations confirmed high binding affinity between pMHC and TCR clones isolated from both sources. CONCLUSIONS: Antigen-specific CD8⁺ T cells from UCB and PB display comparable cytotoxic efficacy against melanoma, albeit with distinct compositional profiles of antigen-specific CD8⁺ T cell subsets. Candidate TCRs can be effectively activated by the tumor-associated antigens MART1 and gp100. This activation promotes the expansion of the available TCR repertoires, thereby mitigating the previous constraint of a limited TCR library. KEY POINTS: Endogenous T-celltherapy for melanoma has used adult peripheral blood as the cell source andachieved certain results, but the cellular components of effector T cells werenot clear. At the same time, it was not clear whether umbilical cord bloodcould be used as a cell resource bank for endogenous T-cell therapy. This studydemonstrated that T cells from umbilical cord blood can be used as a cellresource bank for endogenous T-cell therapy. It further clarified that thereare different components of antigen-specific T cells in umbilical cord bloodand peripheral blood. Antigen-specific T cells from peripheral blood are mainlyproliferative T cells, while those from umbilical cord blood are mainlyeffector T cells and memory T cells. Finally, TCR sequencing was used to obtainTCRs that can target melanoma, expanding the corresponding TCR database.