PRF1 and sarcoma: Further, the cytotoxic capacity of PBMC from STS patients was analyzed by co-culturing of PBMC from STS patients and healthy donors with sarcoma cells (RD-ES, SaOs, and SW1353) in the presence of NKG2D‐CD3/CD16 for 24 h followed by intracellular staining for Perforin and IFNγ.