Author(s): Berg M, Lundqvist A, McCoy P Jr, Samsel L, Fan Y,
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Abstract BACKGROUND AIMS: Cancer immunotherapy involving natural killer (NK) cell infusions and administration of therapeutic agents modulating the susceptibility of tumors to NK-cell lysis has been proposed recently. We provide a method for expanding highly cytotoxic clinical-grade NK cells in vitro for adoptive transfer following bortezomib treatment in patients with advanced malignancies. METHODS: NK cells were expanded with irradiated Epstein-Barr virus-transformed lymphoblastoid cells. Expanded cells were evaluated for their phenotype, cytotoxicity, cytokine secretion, dependence on interleukin (IL)-2 and ability to retain function after cryopreservation. RESULTS: A pure population of clinical-grade NK cells expanded 490+/-260-fold over 21 days. Expanded NK cells had increased TRAIL, FasL and NKG2D expression and significantly higher cytotoxicity against bortezomib-treated tumors compared with resting NK cells. Expanded NK cells, co-cultured with K562 and renal cell carcinoma tumor targets, secreted significantly higher levels of soluble Fas ligand 6; fgjhd IFN-gamma, GM-CSF, TNF-alpha, MIP-1alpha and MIP-1beta compared with resting NK cells. Secretion of the above cytokines and NK-cell cytolytic function were IL-2 dose dependent. Cryopreservation of expanded NK cells reduced expression of NKG2D and TRAIL and NK-cell cytotoxicity, although this effect could be reversed by exposure of NK cells to IL-2. CONCLUSIONS: We describe a method for large-scale expansion of NK cells with increased expression of activating receptors and death receptor ligands resulting in superior cytotoxicity against tumor cells. This ex vivo NK-cell expansion technique is currently being utilized in a clinical trial evaluating the anti-tumor activity of adoptively infused NK cells in combination with bortezomib.
This article was published in Cytotherapy
and referenced in Journal of Carcinogenesis & Mutagenesis