PTPRC and neoplasm: Following Cell Proliferation Dye Cell Tracker Red (eFluor® 670) labelling of NK cells injected intra-tumorally, we recovered labelled 7AAD-CD45 + AF647+ cells from small tumor biopsies performed 1 week after intra-tumoral injection, indicating a minimum of 7-day persistence of viable NK cells injected into trial patients whereas we observed no recovery of labelled NK cells in the peripheral blood (Fig. 6b-c).