Contributions
Abstract: EP942
Type: E-Poster Presentation
Session title: Myeloma and other monoclonal gammopathies - Biology & Translational Research
Background
Antibody-dependent cellular toxicity (ADCC) is among predominant MOAs of anti-CD38 and anti-SLAMF7 therapeutic monoclonal antibodies (mAbs), which is augmented with IMiDs, lenalidomide (LEN) and pomalidomide (POM). However, effector function of immune cells is attenuated and exhausted in patients with MM, especially after repeated relapses or elderly frail patients, which hampers clinical efficacy of these therapeutic mAbs. To overcome this issue, we have been studying the utilization of γδ T cells for MM treatment. Human γδ T cells are important effectors in the first-line defense against infection and tumors, and we reported that such expanded γδ T cells effectively target and impair not only MM cells but also osteoclasts (OCs) (Cui, et al. IJH 2011) and that LEN and POM are able to activate and expand Th1-like γδ T cells and enhance their cytotoxic activity against MM cells in combination with recombinant phosphoantigens as well as zoledronic acid (Harada et al. Leukemia 2017).
Aims
The present study was undertaken to explore the effects of anti-CD38 and anti-SLAMF7 therapeutic mAbs on cytotoxic activity of the expanded human Th1-like γδ T cells against OCs and MM cells.
Methods
Th1-like γδ T cells were expanded from peripheral blood mononuclear cells (PBMCs) ex vivo by aminobisphosphonates in combination with IL-2. OCs were induced from PBMCs or isolated monocytes using M-CSF plus RANK ligand. The suface markes and protein expression were detected by flow cytometry and Western blotting.
Results
The expanded Th1-like γδ T cells highly expressed CD16, FcγRIIIa, together with perforin and granzymeB as well as the cytotoxicity-associated costimulatory molecules NKG2D and DNAX accessory molecule-1 (DNAM-1; CD226), similar to NK cells. The expanded Th1-like γδ T cells exerted direct cytotoxic activity towards OCs as well as MM cells. Addition of the anti-SLAMF7 mAb elotuzumab (ELO) further increased the cytotoxic activity of Th1-like γδ T cells against SLAMF7-expressing MM.1S and OPM-2 cells but not RPMI 8226 cells with marginal SLAMF7 expression, indicating induction of ADCC activity by Th1-like γδ T cells in combination with ELO. Induction of ADCC activity by Th1-like γδ T cells was much more potent with ELO compared to anti-CD38 therapeutic mAbs, daratumumab and isatuximab, suggesting suitability of Th1-like γδ T cells for ADCC induction with ELO. Interestingly, cytotoxic activity of Th1-like γδ T cells against OCs was also augmented in combination with ELO, although ELO alone did not show any cytotoxic activity against OCs, indicating the emergence of ELO’s ADCC with Th1-like γδ T cells towards OCs. SLAMF7 expression was induced and robustly upregulated during osteoclastic differentiation from monocytes with M-CSF and RANK ligand, and ELO could target preOCs as well as OCs. MM cells interact with OCs to form vicious cycle between MM cell growth and osteoclastogenesis (Abe, et al. Blood 2004); however, ELO markedly potentiated the γδ T cell-induced cell death against both MM cells and OCs in their cocultures.
Conclusion
These results collectively demonstrate that SLAMF7 is highly expressed in both MM cells and OCs, and that OCs as well as MM cells are susceptible to ELO’s ADCC with Th1-like γδ T cells. Further study is warranted on ELO’s ADCC activity for ambient cells in MM bone marrow and effective revitalization and expansion of Th1-like γδ T cells to make the better use of ELO’s ADCC activity.
Keyword(s): ADCC, Immune therapy, Myeloma, Osteoclast
Abstract: EP942
Type: E-Poster Presentation
Session title: Myeloma and other monoclonal gammopathies - Biology & Translational Research
Background
Antibody-dependent cellular toxicity (ADCC) is among predominant MOAs of anti-CD38 and anti-SLAMF7 therapeutic monoclonal antibodies (mAbs), which is augmented with IMiDs, lenalidomide (LEN) and pomalidomide (POM). However, effector function of immune cells is attenuated and exhausted in patients with MM, especially after repeated relapses or elderly frail patients, which hampers clinical efficacy of these therapeutic mAbs. To overcome this issue, we have been studying the utilization of γδ T cells for MM treatment. Human γδ T cells are important effectors in the first-line defense against infection and tumors, and we reported that such expanded γδ T cells effectively target and impair not only MM cells but also osteoclasts (OCs) (Cui, et al. IJH 2011) and that LEN and POM are able to activate and expand Th1-like γδ T cells and enhance their cytotoxic activity against MM cells in combination with recombinant phosphoantigens as well as zoledronic acid (Harada et al. Leukemia 2017).
Aims
The present study was undertaken to explore the effects of anti-CD38 and anti-SLAMF7 therapeutic mAbs on cytotoxic activity of the expanded human Th1-like γδ T cells against OCs and MM cells.
Methods
Th1-like γδ T cells were expanded from peripheral blood mononuclear cells (PBMCs) ex vivo by aminobisphosphonates in combination with IL-2. OCs were induced from PBMCs or isolated monocytes using M-CSF plus RANK ligand. The suface markes and protein expression were detected by flow cytometry and Western blotting.
Results
The expanded Th1-like γδ T cells highly expressed CD16, FcγRIIIa, together with perforin and granzymeB as well as the cytotoxicity-associated costimulatory molecules NKG2D and DNAX accessory molecule-1 (DNAM-1; CD226), similar to NK cells. The expanded Th1-like γδ T cells exerted direct cytotoxic activity towards OCs as well as MM cells. Addition of the anti-SLAMF7 mAb elotuzumab (ELO) further increased the cytotoxic activity of Th1-like γδ T cells against SLAMF7-expressing MM.1S and OPM-2 cells but not RPMI 8226 cells with marginal SLAMF7 expression, indicating induction of ADCC activity by Th1-like γδ T cells in combination with ELO. Induction of ADCC activity by Th1-like γδ T cells was much more potent with ELO compared to anti-CD38 therapeutic mAbs, daratumumab and isatuximab, suggesting suitability of Th1-like γδ T cells for ADCC induction with ELO. Interestingly, cytotoxic activity of Th1-like γδ T cells against OCs was also augmented in combination with ELO, although ELO alone did not show any cytotoxic activity against OCs, indicating the emergence of ELO’s ADCC with Th1-like γδ T cells towards OCs. SLAMF7 expression was induced and robustly upregulated during osteoclastic differentiation from monocytes with M-CSF and RANK ligand, and ELO could target preOCs as well as OCs. MM cells interact with OCs to form vicious cycle between MM cell growth and osteoclastogenesis (Abe, et al. Blood 2004); however, ELO markedly potentiated the γδ T cell-induced cell death against both MM cells and OCs in their cocultures.
Conclusion
These results collectively demonstrate that SLAMF7 is highly expressed in both MM cells and OCs, and that OCs as well as MM cells are susceptible to ELO’s ADCC with Th1-like γδ T cells. Further study is warranted on ELO’s ADCC activity for ambient cells in MM bone marrow and effective revitalization and expansion of Th1-like γδ T cells to make the better use of ELO’s ADCC activity.
Keyword(s): ADCC, Immune therapy, Myeloma, Osteoclast