STABLE TRANSDUCTION OF THE INTERLEUKIN-2 GENE INTO HUMAN NATURAL-KILLER-CELL LINES AND THEIR PHENOTYPIC AND FUNCTIONAL-CHARACTERIZATION IN-VITRO AND IN-VIVO

A variety of strategies have been attempted in the past to stably tran sduce natural killer (MK) cells with cytokine or other cellular genes. Here, we demonstrate the successful delivery of the interleukin-2 (IL -2) gene into two human NK cell lines, IL-2-dependent NK-92 and IL-2-i ndependent YT, by retroviral transduction, An MuLV-based retroviral ve ctor expressing human IL-2 and neo(r) markers from a polycistronic mes sage was constructed and transduced into a GRIP packaging cell line, B y coincubation of NK cells with monolayers of GRIP cells or by using r etrovirus-containing supernatants in a flow-through method, 10% to 20% of NK cells were stably transduced. Upon selection in the presence of increasing G418 concentrations, transduced NK cells were able to prol iferate independently of IL-2 for more than 5 months and to secrete up to 5.5 ng/10(6) cells/24 h of IL-2. IL-2 gene-transduced NK-92 cells had an in vitro cytotoxicity against tumor targets that was significan tly higher than that of parental cells and secreted interferon gamma ( IFN gamma) and tumor necrosis factor alpha (TNF alpha) in addition to IL-2. Moreover, the in vivo antitumor activity of IL-2 gene-transduced NK-92 cells against established 3-day liver metastases in mice was gr eater than that of parental nontransduced NK cells. Stable expression of the IL-2 transgene in NK cells improved their therapeutic potential in tumor-bearing hosts. Thus, transduced NK cells secreted sufficient quantities of bioactive IL-2 to proliferate in vitro and mediated the antitumor effects both in vitro and in vivo in the absence of exogeno us IL-2. These results suggest that genetic modification of NK cells e x vivo could be useful for clinical cancer therapy in the future. (C) 1998 by The American Society of Hematology.