PD-1 Blockade Reinvigorates Bone Marrow CD8 T Cells from Patients with Multiple Myeloma in the Presence of TGFβ Inhibitors.

PURPOSE

Immune-checkpoint inhibitors have shown therapeutic efficacy in various malignant diseases. However, anti-programmed death (PD)-1 therapy has not shown clinical efficacy in multiple myeloma.

EXPERIMENTAL DESIGN

Bone marrow (BM) mononuclear cells were obtained from 77 newly diagnosed multiple myeloma patients. We examined the expression of immune-checkpoint receptors in BM CD8 T cells and their functional restoration by treatment with anti-PD-1 and TGFβ inhibitors.

RESULTS

We confirmed the upregulation of PD-1 and PD-L1 expression in CD8 T cells and myeloma cells, respectively, from the BM of multiple myeloma patients. PD-1-expressing CD8 T cells from the BM of multiple myeloma patients coexpressed other checkpoint inhibitory receptors and exhibited a terminally differentiated phenotype. These results were also observed in BM CD8 T cells specific to myeloma antigens NY-ESO-1 and HM1.24. BM CD8 T cells from multiple myeloma patients exhibited reduced proliferation and cytokine production upon T-cell receptor stimulation. However, anti-PD-1 did not increase the proliferation of BM CD8 T cells from multiple myeloma patients, indicating that T-cell exhaustion in multiple myeloma is hardly reversed by PD-1 blockade alone. Intriguingly, anti-PD-1 significantly increased the proliferation of BM CD8 T cells from multiple myeloma patients in the presence of inhibitors of TGFβ, which was overexpressed by myeloma cells.

CONCLUSIONS

Our findings indicate that combined blockade of PD-1 and TGFβ may be useful for the treatment of multiple myeloma.