Contributions
Abstract: EP943
Type: E-Poster Presentation
Session title: Myeloma and other monoclonal gammopathies - Biology & Translational Research
Background
Multiple myeloma is an incurable plasma cell malignancy and identifying mechanisms driving disease progression is crucial for future development of novel therapies. Immune-mediated control of tumor progression is an important factor in many malignancies, yet the cells and signals that constitute an effective anti-myeloma immune response are incompletely defined.
Aims
To identify immune-related mechanisms of disease progression in experimental multiple myeloma.
Methods
Intravenous transfer of 106 5TGM1-GFP murine myeloma cells into KaLwRij mice leads to myeloma development in 3 weeks. In contrast, C57BL/6 mice are reported to be resistant to myeloma development. We used both mouse strains and monitored tumor development through serum M-protein levels. Bone marrow and spleen were harvested to analyze the immune microenvironment and determine tumor dissemination with flow cytometry and histology.
Results
Myeloma was defined by >5% tumor cells in BM, presence of tumor cells in the spleen and detection of M-protein >2 mg/ml. In KaLwRij mice, myeloma developed in 100% (14/14) of mice while C57BL/6 mice did not develop myeloma based on these criteria. Interestingly, 65% (9/14) of C57BL/6 mice presented with myeloma cells in the bone marrow, but with significantly lower tumor load (M-protein 1.1 mg/ml vs. 5.8 mg/ml) compared to KaLwRij mice. This low tumor burden remained stable and was confined to the bone marrow, without any splenic involvement, suggestive of active tumor restraint. To identify the mechanism of successful immunological containment of myeloma cells, we compared the cytotoxic immune response in C57BL/6 and KaLwRij mice. In both murine strains, NK cell activation was apparent, with upregulation of early activation markers such as CD69 in response to tumor presence. In contrast, while activation was accompanied by an increase in NK cell numbers in the C57BL/6 mice, this expansion was absent from KaLwRij mice. Similarly, CD8+ T cell activation and an increase in number of CD11b+ recently activated CD8+ T cells was present in C57BL/6 mice, yet absent from KaLwRij mice.
These data suggest a combined innate and adaptive immune-mediated control of multiple myeloma in C57BL/6 mice. To determine the stability of this immune-mediated control of multiple myeloma we followed C57BL/6 mice injected with 5TGM1 myeloma cells over time while monitoring tumor load through serum M protein. At 6 weeks post injection, 71% (5/7) of the C57BL/6 mice with low tumor load at 3 weeks had developed progressive disease, with serum M protein levels > 2 mg/ml and >5% myeloma cells in the bone marrow. Reassessing cytotoxic immune responses in myeloma-bearing C57BL/6 mice revealed a stark decline in absolute numbers of activated NK cells, very similar to the phenotype in KaLwRij mice. Interestingly, loss of CD8+ T cells was seen in about half (2/5) of the C57BL/6 mice and was associated with loss of bone marrow-containment and the appearance of myeloma cells in the spleen.
Conclusion
Failure to mount adequate anti-myeloma immune responses is one of the drivers of disease development in KaLwRij mice. Transfer of 5TGM1 myeloma cells in C57BL/6 mice leads to tumor control via expansion of innate and adaptive immune cells. With time, immune-mediated restraint of multiple myeloma fails, exemplified by loss of NK cell and CD8+T cell expansion, culminating in tumor outgrowth and systemic dissemination. This model will allow generation of novel insights into the mechanisms of immune escape by multiple myeloma cells.
Keyword(s): CD8 T cells, Myeloma, NK cell
Abstract: EP943
Type: E-Poster Presentation
Session title: Myeloma and other monoclonal gammopathies - Biology & Translational Research
Background
Multiple myeloma is an incurable plasma cell malignancy and identifying mechanisms driving disease progression is crucial for future development of novel therapies. Immune-mediated control of tumor progression is an important factor in many malignancies, yet the cells and signals that constitute an effective anti-myeloma immune response are incompletely defined.
Aims
To identify immune-related mechanisms of disease progression in experimental multiple myeloma.
Methods
Intravenous transfer of 106 5TGM1-GFP murine myeloma cells into KaLwRij mice leads to myeloma development in 3 weeks. In contrast, C57BL/6 mice are reported to be resistant to myeloma development. We used both mouse strains and monitored tumor development through serum M-protein levels. Bone marrow and spleen were harvested to analyze the immune microenvironment and determine tumor dissemination with flow cytometry and histology.
Results
Myeloma was defined by >5% tumor cells in BM, presence of tumor cells in the spleen and detection of M-protein >2 mg/ml. In KaLwRij mice, myeloma developed in 100% (14/14) of mice while C57BL/6 mice did not develop myeloma based on these criteria. Interestingly, 65% (9/14) of C57BL/6 mice presented with myeloma cells in the bone marrow, but with significantly lower tumor load (M-protein 1.1 mg/ml vs. 5.8 mg/ml) compared to KaLwRij mice. This low tumor burden remained stable and was confined to the bone marrow, without any splenic involvement, suggestive of active tumor restraint. To identify the mechanism of successful immunological containment of myeloma cells, we compared the cytotoxic immune response in C57BL/6 and KaLwRij mice. In both murine strains, NK cell activation was apparent, with upregulation of early activation markers such as CD69 in response to tumor presence. In contrast, while activation was accompanied by an increase in NK cell numbers in the C57BL/6 mice, this expansion was absent from KaLwRij mice. Similarly, CD8+ T cell activation and an increase in number of CD11b+ recently activated CD8+ T cells was present in C57BL/6 mice, yet absent from KaLwRij mice.
These data suggest a combined innate and adaptive immune-mediated control of multiple myeloma in C57BL/6 mice. To determine the stability of this immune-mediated control of multiple myeloma we followed C57BL/6 mice injected with 5TGM1 myeloma cells over time while monitoring tumor load through serum M protein. At 6 weeks post injection, 71% (5/7) of the C57BL/6 mice with low tumor load at 3 weeks had developed progressive disease, with serum M protein levels > 2 mg/ml and >5% myeloma cells in the bone marrow. Reassessing cytotoxic immune responses in myeloma-bearing C57BL/6 mice revealed a stark decline in absolute numbers of activated NK cells, very similar to the phenotype in KaLwRij mice. Interestingly, loss of CD8+ T cells was seen in about half (2/5) of the C57BL/6 mice and was associated with loss of bone marrow-containment and the appearance of myeloma cells in the spleen.
Conclusion
Failure to mount adequate anti-myeloma immune responses is one of the drivers of disease development in KaLwRij mice. Transfer of 5TGM1 myeloma cells in C57BL/6 mice leads to tumor control via expansion of innate and adaptive immune cells. With time, immune-mediated restraint of multiple myeloma fails, exemplified by loss of NK cell and CD8+T cell expansion, culminating in tumor outgrowth and systemic dissemination. This model will allow generation of novel insights into the mechanisms of immune escape by multiple myeloma cells.
Keyword(s): CD8 T cells, Myeloma, NK cell