Multiple myeloma (MM) is an incurable plasma cell malignancy. NK cells have demonstrated anti-MM activity in allogeneic transplants and donor lymphocyte infusions, and may provide a more effective therapy for MM. This work demonstrates cytotoxicity of NK-92 and KHYG-1 against MM cells in chromium release and flow cytometry cytotoxicity assays. At a 10:1 effector to target ratio, the cytotoxicity of NK cell lines against MM cells is 50-90%. Blocking NKp30 significantly reduces the cytotoxicity of NK-92 and KHYG-1, while blocking NKG2D and DNAM-1 only reduces the cytotoxicity of NK-92. Notably, NK-92 and KHYG-1 have shown preferential cytotoxicity against the clonogenic population, killing 89-99% in a methylcellulose cytotoxicity assay. Preliminary results in a xenograft bioluminescent mouse model show that NK-92, but not KHYG-1, reduces the tumor burden detected by bioluminescence imaging and bone marrow engraftment by flow cytometry. Therefore, NK cell lines may offer a more effective therapy for MM.

Multiple myeloma (MM) is an incurable plasma cell malignancy. NK cells have demonstrated anti-MM activity in allogeneic transplants and donor lymphocyte infusions, and may provide a more effective therapy for MM. This work demonstrates cytotoxicity of NK-92 and KHYG-1 against MM cells in chromium release and flow cytometry cytotoxicity assays. At a 10:1 effector to target ratio, the cytotoxicity of NK cell lines against MM cells is 50-90%. Blocking NKp30 significantly reduces the cytotoxicity of NK-92 and KHYG-1, while blocking NKG2D and DNAM-1 only reduces the cytotoxicity of NK-92. Notably, NK-92 and KHYG-1 have shown preferential cytotoxicity against the clonogenic population, killing 89-99% in a methylcellulose cytotoxicity assay. Preliminary results in a xenograft bioluminescent mouse model show that NK-92, but not KHYG-1, reduces the tumor burden detected by bioluminescence imaging and bone marrow engraftment by flow cytometry. Therefore, NK cell lines may offer a more effective therapy for MM.