Natural killer cell lines preferentially kill clonogenic multiple myeloma cells and decrease myeloma engraftment in a
Brenna E Swift1, Brent A Williams, Yoko Kosaka
1Cell Therapy Program, Princess Margaret Hospital, 610 University Ave, Toronto, ON, Canada.
Background:
Novel therapies capable of targeting drug resistant clonogenic MM cells are required for more effective treatment of multiple myeloma. This study investigates the cytotoxicity of natural killer cell lines against bulk and clonogenic multiple myeloma and evaluates the tumor burden after NK cell therapy in a bioluminescent xenograft mouse model.
Design And Methods:
The cytotoxicity of natural killer cell lines was evaluated against bulk multiple myeloma cell lines using chromium release and flow cytometry cytotoxicity assays. Selected activating receptors on natural killer cells were blocked to determine their role in multiple myeloma recognition. Growth inhibition of clonogenic multiple myeloma cells was assessed in a methylcellulose clonogenic assay in combination with secondary replating to evaluate the self-renewal of residual progenitors after natural killer cell treatment. A bioluminescent mouse model was developed using the human U266 cell line transduced to express green fluorescent protein and luciferase (U266eGFPluc) to monitor disease progression in vivo and assess bone marrow engraftment after intravenous NK-92 cell therapy.
Results:
Three multiple myeloma cell lines were sensitive to NK-92 and KHYG-1 cytotoxicity mediated by NKp30, NKp46, NKG2D and DNAM-1 activating receptors. NK-92 and KHYG-1 demonstrated 2- to 3-fold greater inhibition of clonogenic multiple myeloma growth, compared with killing of the bulk tumor population. In addition, the residual colonies after treatment formed significantly fewer colonies compared to the control in a secondary replating for a cumulative clonogenic inhibition of 89-99% at the 20:1 effector to target ratio. Multiple myeloma tumor burden was reduced by NK-92 in a xenograft mouse model as measured by bioluminescence imaging and reduction in bone marrow engraftment of U266eGFPluc cells by flow cytometry.
Conclusions:
This study demonstrates that NK-92 and KHYG-1 are capable of killing clonogenic and bulk multiple myeloma cells. In addition, multiple myeloma tumor burden in a xenograft mouse model was reduced by intravenous NK-92 cell therapy. Since multiple myeloma colony frequency correlates with survival, our observations have important clinical implications and suggest that clinical studies of NK cell lines to treat MM are warranted.
Insights
Natural killer (NK) cells effectively target and reduce both bulk and drug-resistant clonogenic multiple myeloma (MM) cells. NK cell therapy also decreased tumor burden in a mouse model, showing promise for MM treatment.
Area of Science:
- Immunology
- Hematology
- Cancer Biology
Background:
- Multiple myeloma (MM) treatment requires novel therapies targeting drug-resistant clonogenic cells.
- Natural killer (NK) cells are investigated as a potential therapeutic approach.
Purpose of the Study:
- To assess the cytotoxicity of NK cell lines against bulk and clonogenic MM cells.
- To evaluate the efficacy of NK cell therapy in reducing MM tumor burden in a preclinical model.
Main Methods:
- Cytotoxicity assays (chromium release, flow cytometry) were used to evaluate NK cell activity against MM cell lines.
- Clonogenic assays assessed the inhibition of self-renewal in residual MM progenitors post-NK cell treatment.
- A bioluminescent xenograft mouse model (U266eGFPluc) monitored disease progression and bone marrow engraftment after NK-92 cell therapy.
Main Results:
- NK-92 and KHYG-1 cell lines demonstrated significant cytotoxicity against MM cells, mediated by activating receptors (NKp30, NKp46, NKG2D, DNAM-1).
- NK cells exhibited 2- to 3-fold greater inhibition of clonogenic MM growth compared to bulk populations, achieving 89-99% cumulative inhibition.
- Intravenous NK-92 cell therapy reduced MM tumor burden and bone marrow engraftment in a xenograft mouse model.
Conclusions:
- NK-92 and KHYG-1 cell lines effectively kill both bulk and clonogenic multiple myeloma cells.
- NK cell therapy reduced tumor burden in a preclinical model, suggesting clinical relevance.
- Clinical studies of NK cell therapy for multiple myeloma are warranted due to the correlation between colony frequency and survival.
