(P 249) IN VITRO EXPANSION OF TUMOR-INFILTRATING GAMMA-DELTA T-CELLS FROM PATIENTS WITH SOFT TISSUE SARCOMAS

Objective: The role of γδ T-cells in anti-tumor immunity remains complex and not fully elucidated. Their MHC-independent target cell recognition distinguishes them from αβ T-cells, positioning them as promising candidates for novel immunotherapies, including adoptive cell transfer. In this study, we aimed to expand tumor-infiltrating γδ T-cells from sarcoma samples and conduct in vitro phenotypic and functional analyses.

Methods: Patients with detectable tumor-infiltrating γδ T-cells were identified from our institutional biobank, which includes samples (e.g. in vitro expanded TILs) from patients who underwent surgery for primary or recurrent soft tissue sarcoma. TILs were expanded from fresh tumor tissue using IL-2-supplemented culture medium. TIL samples exhibiting a substantial proportion of γδ T-cells (> 10%) were selected for this sub-study. Phenotypic and functional characterization was performed using flow cytometry.

Results: We identified nine samples containing a significant population of γδ T-cells, originating from patients with undifferentiated pleomorphic sarcoma, leiomyosarcoma, myxoid liposarcoma, and pleomorphic liposarcoma. The median TIL expansion time was 29 days (range: 22-42 days). The proportion of γδ T-cells within the total TIL product ranged from 10% to 60%, corresponding to an absolute number of 12-68 million cells. Phenotypic analysis revealed that the majority of γδ T-cells displayed a CD3+CD4-CD8- or CD3+CD8+CD4- phenotype. Notably, in one sample from a patient with undifferentiated pleomorphic sarcoma, a subset of γδ T-cells demonstrated in vitro tumor recognition, as evidenced by IFNγ and/or TNFα production upon co-culture with autologous tumor cells.

Conclusion: Our findings demonstrate that some soft tissue sarcomas are infiltrated by tumor-reactive γδ T-cells capable of in vitro expansion using clinically established methods. This suggests a role for γδ T-cells in the anti-tumor immune response and highlights the potential relevance of γδ T-cell-based immunotherapy for specific sarcoma subtypes.