Purpose: Adoptive natural killer (NK) cell immunotherapy is a promising approach for the treatment of malignancies. The difficulty to culture NK cells from advanced cancer patients has been the limiting factor for generating sufficient cell numbers for autologous adoptive NK cell therapy. The aim of this study was to find the role of feeder cells in expanding NK cells ex vivo. Experimental Design: NK cells (CD3CD56+) were isolated from peripheral blood mononuclear cells of healthy volunteers (HV) and cancer patients (CP) using immune magnetic beads, and NK-negative fractions were used as feeder cells. Purified NK cells (0.2 x 106) were co-cultured with 4 x 106 feeder cells in fresh AIM-V media supplemented with 10 ng/mL anti-CD3 mAb, 5% human serum and 1000 unit/mL IL-2. On day 5 of culture, the anti-CD3 mAb-containing medium was washed out, and fresh medium with IL-2 was added regularly throughout the culturing period. Culture groups were compared for the fold-expansion, NK purity, cytotoxicity, and receptor expression patterns of expansion products. To characterize feeder cells, NK-negative fractions were α-irradiated and then were cultivated in the anti-CD3 mAb-containing medium for 3 days. Results: Fold expansion of NK cells co-cultured with feeder cells from HV (feeder- HV) was higher than with feeder cells from cancer patients (feeder-CP). During the 14 days period of culture, NK cells from advanced cancer patients co-cultivated with feeder-HV had expanded on average 299.6-fold (range: 21- to 620-fold). On the other hand, those co-cultivated with feeder-CP had expanded only on average 169.4-fold (range: 4.2- to 575-fold). The proportion of CD3CD56+ NK cells in expanded cell cultures with feeder-HV was significantly higher than that in cultures containing feeder-CP. Cultures grown in the presence of feeder-HV contained 93.8% ± 7.0 (mean ± SD; n = 6) of CD3CD56+ NK cells and those in the presence of feeder-CP, 83.6% ± 15.9. Cytotoxicity and receptor expression patterns were not significantly different among the groups. All of them were more cytotoxic in comparison to the freshly isolated NK cells. Feeder-HV used in this study presented relative increase (% day 3 - % day 0) in CD3+CD4+T cells (31.3% ± 5.7; n = 4), while the feeder-CP showed no relative change. In addition, IL-15, a cytokine inducing cell proliferation of NK cells, was detected in the culture supernatants of feeder-HV (53.8 pg/mL ± 29.2), but not in feeder-CP. Conclusions: Feeder cells obtained from healthy volunteers have the potential to expand and activate the NK cells from advanced cancer patients. The NK cell expansion method described in here provides a good basis for acquiring the large numbers of highly active NK cells from cancer patients for autologous adoptive immunotherapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3514. doi:1538-7445.AM2012-3514