ALL STEM CELLS

http://www.jimmunol.org/cgi/content/full/181/5/3449

Adoptive Transfer of Gene-Modified Primary NK Cells Can
Specifically Inhibit Tumor Progression In Vivo

NK cells hold great potential for improving the immunotherapy of cancer. Nevertheless, tumor cells can effectively escape NK cell-mediated apoptosis through interaction of MHC molecules with NK cell inhibitory receptors. Thus, to harness NK cell effector function against tumors, we used Amaxa gene transfer technology to gene-modify primary mouse NK cells with a chimeric single-chain variable fragment (scFv) receptor specific for the human erbB2 tumor-associated Ag. The chimeric receptor was composed of the extracellular scFv anti-erbB2 Ab linked to the transmembrane and cytoplasmic CD28 and TCR-ζ signaling domains (scFv-CD28-ζ). In this study we demonstrated that mouse NK cells gene-modified with this chimera could specifically mediate enhanced killing of an erbB2⁺ MHC class I⁺ lymphoma in a perforin-dependent manner. Expression of the chimera did not interfere with NK cell-mediated cytotoxicity mediated by endogenous NK receptors. Furthermore, adoptive transfer of gene-modified NK cells significantly enhanced the survival of RAG mice bearing established i.p. RMA-erbB2⁺ lymphoma. In summary, these data suggest that use of genetically modified NK cells could broaden the scope of cancer immunotherapy for patients.

In summary, we have demonstrated high level expression of the scFv anti-erbB2-CD28-ζ chimeric receptor in primary mouse NK cells and that adoptive transfer of these cells could mediate Ag-specific tumor inhibition in vivo. The use of this receptor containing the CD28 costimulatory signaling molecule was appropriate for mouse NK cells given that CD28-mediated signaling has been demonstrated in these cells (51, 52). However, the incorporation of other signaling domains into the receptor may result in even better activation of NK cells. An anti-CD19 scFv chimeric receptor containing the 4-1BB signaling domain linked in tandem with the TCR-ζ domain was shown to enhance human NK cell function compared with receptors containing either TCR-ζ or DAP10-signaling domains alone (28). Whether this type of receptor incorporating the 4-1BB signaling domain can enhance NK cell function and anti-tumor effects in vivo warrants further investigation. Previous studies have shown superior functional activity and trafficking by CD27^hi NK cells (53). Thus comparison of different gene modified NK cell subsets (CD27^hi vs CD27^lo) may identify which subset to use for achieving optimal therapeutic effects. Overall, the results of this study have highlighted that use of gene-modified NK cells to overcome HLA-mediated inhibition is a novel and exciting prospect for cancer immunotherapy.