Supplementary Figure S2 PDF file - 39K, A standard 51Cr release assay was performed using K562, U937 or KL-1 as target cell lines, as described in the "Materials and Methods" section. These targets were labeled with 51Cr (Perkin Elmer, Boston, MA, USA) at 50 ��Ci/5 �~ 105 cells and incubated at 5 �~ 103 cells/well with resting human NK cells at E:T ratios of 30:1, 10:1 and 3:1. Percent specific lysis was calculated as follows: 100 �~ (experimental release-spontaneous release)/(maximum release-spontaneous release)
ARTICLE ABSTRACTAdoptive natural killer (NK) cell therapy may offer an effective treatment regimen for cancer patients whose disease is refractory to conventional therapy. NK cells can kill a wide range of tumor cells by patterned recognition of target ligands. We hypothesized that tumor targets sensitive to NK lysis would drive vigorous expansion of NK cells from human peripheral blood mononuclear cells (PBMC). Here, we provide the basis for developing a novel ex vivo expansion process. By screening class I–negative or –mismatched tumor cell lines we identified a Jurkat T-lymphoblast subline termed KL-1, which was highly effective in specifically expanding NK cells. KL-1 addition to PBMC cultures achieved approximately 100-fold expansion of NK cells with nearly 90% purity, accompanied by reciprocal inhibition of T-cell growth. Marked elevations in expression of activation receptors, natural cytotoxicity receptors (NKp30, NKp44), and adhesion molecules (CD11a, ICAM-1) were associated with high tumor-lytic capacity, in both in vitro and in vivo models. KL-1–mediated expansion of NK cells was contact dependent and required interactions with CD16, the Fcγ receptor on NK cells, with ligands that are expressed on B cells. Indeed, B-cell depletion during culture abrogated selective NK cell expansion, while addition of EBV-transformed B cells further augmented NK expansion to approximately 740-fold. Together, our studies define a novel method for efficient activation of human NK cells that employs KL-1–lysed tumor cells and cocultured B cells, which drive a robust expansion of potent antitumor effector cells that will be useful for clinical evaluation. Cancer Res; 73(8); 2598–607. ©2012 AACR.