CD70 and myeloid leukemia: Next, NK cells were sorted according to their expression of CD8α and CD70 and tested for their cytotoxicity against classical NK target cell lines 721.221 (B cell lymphoma) and K562 (myeloid leukaemia), as well as non-hematological tumor cell lines PC3 (prostate), A549 (lung) and Colo829 (melanoma).