Enhanced Cytotoxicity And Underlying Mechanism Of Ex Vivo Expanded Natural Killer Cells Against Breast Cancer Cells

Despite significant advances in treatment, breast cancer, especially the metastatic breast cancer, usually can't be cured by current therapies and has a poor prognosis. To develop more effective therapy for patients with breast cancer, we examined the potential of ex vivo expanded natural killer (NK) cells to exert anti-tumor cytotoxicity. We used K562-mb15-41BBL cells to expand NK cells from peripheral blood mononuclear cells (PBMCs) of healthy donors (HD). We then investigated the expression of NK cell receptors and NK cell cytotoxicity against breast cancer cell lines MCF-7, MDA-MB-231, MDA-MB-468 and patient breast cancer cells (n=4), with and without the addition of neutralizing antibodies. As a result, NK cells were sharply expanded to a mean of 254.4-fold (range: 93.4-436.7, n=8). Cell expansion led to NK cell receptor activation, with remarkable up-regulation of activating molecules NK-G2D, NKp30, NKp44, CD26, CD69, CD70 and DNAM-1, and resulted in enhanced cytotoxicity against three breast cancer cell lines and primary breast cancer cells (n=4), while sparing patients' normal PBMCs. Blocking studies confirmed that allogeneic NK cell cytotoxicity is established through these multiple activating receptor-ligand interactions. Taken together, the present study demonstrates that large numbers of NK cells with potent cytotoxicity against breast cancer cells can be generated from PBMCs of HD, providing a necessary preclinical evidence for clinical evaluation of these ex vivo expanded NK cells in patients with breast cancer.