T cells in multiple myeloma display features of exhaustion and senescence at the tumor site.
Multiple myeloma is an incurable plasma cell malignancy that is mostly restricted to the bone marrow. Cancer-induced dysfunction of cytotoxic T cells at the tumor site may be responsible for immune evasion and therapeutical failure of immunotherapies. Therefore, enhanced knowledge about the actual status of T cells in myeloma bone marrow is urgently needed. Here, we assessed the expression of inhibitory molecules PD-1, CTLA-4, 2B4, CD160, senescence marker CD57, and CD28 on T cells of naive and treated myeloma patients in the bone marrow and peripheral blood and collected data on T cell subset distribution in both compartments. In addition, T cell function concerning proliferation and expression of T-bet, IL-2, IFNγ, and CD107a was investigated after in vitro stimulation by CD3/CD28. Finally, data was compared to healthy, age-matched donor T cells from both compartments.



Multicolor flow cytometry was utilized for the analyses of surface molecules, intracellular staining of cytokines was also performed by flow cytometry, and proliferation was assessed by3H-thymidine incorporation. Statistical analyses were performed utilizing unpaired T test and Mann-Whitney U test.



We observed enhanced T cell exhaustion and senescence especially at the tumor site. CD8+ T cells expressed several molecules associated with T cell exhaustion (PD-1, CTLA-4, 2B4, CD160) and T cell senescence (CD57, lack of CD28). This phenotype was associated with lower proliferative capacity and impaired function. Despite a high expression of the transcription factor T-bet, CD8+ T cells from the tumor site failed to produce IFNγ after CD3/CD28 in vitro restimulation and displayed a reduced ability to degranulate in response to T cell stimuli. Notably, the percentage of senescent CD57+CD28- CD8+ T cells was significantly lower in treated myeloma patients when compared to untreated patients.



T cells from the bone marrow of myeloma patients were more severely impaired than peripheral T cells. While our data suggest that terminally differentiated cells are preferentially deleted by therapy, immune-checkpoint molecules were still present on T cells supporting the potential of checkpoint inhibitors to reactivate T cells in myeloma patients in combination therapies. However, additional avenues to restore anti-myeloma T cell responses are urgently needed.
Tyrolean Cancer Research Institute, Innrain 66, 6020, Innsbruck, Austria.
Claudia
C
Zelle-Rieser
Tyrolean Cancer Research Institute, Innrain 66, 6020, Innsbruck, Austria.
Shanmugapriya
S
Thangavadivel
Department of Orthopedic Surgery, Medical University of Innsbruck, Anichstraße 35, Innsbruck, Austria.
Rainer
R
Biedermann
Department of Pathology, Medical University of Innsbruck, Müllerstraße 44, Innsbruck, Austria.
Andrea
A
Brunner
Department of Dermatology, Venereology and Allergology, Medical University of Innsbruck, Anichstraße 35, Innsbruck, Austria.
Patrizia
P
Stoitzner
Department of Internal Medicine V, Medical University of Innsbruck, Anichstraße 35, Innsbruck, Austria.
Ella
E
Willenbacher
Tyrolean Cancer Research Institute, Innrain 66, 6020, Innsbruck, Austria.|Salzburg Cancer Research Institute (SCRI), Müllner Hauptstraße 48, 5020, Salzburg, Austria.|Third Medical Department at The Paracelsus Medical University Salzburg, Müllner Hauptstraße 48, Salzburg, Austria.
Richard
R
Greil
Tyrolean Cancer Research Institute, Innrain 66, 6020, Innsbruck, Austria. Karin.Joehrer@tkfi.at.
Karin
K
Jöhrer
D000368:Aged; D001773:Blood Cells; D001854:Bone Marrow Cells; D018414:CD8-Positive T-Lymphocytes / Q000473:pathology; D016022:Case-Control Studies; D049109:Cell Proliferation; D016922:Cellular Senescence; D005260:Female; D006801:Humans; D016130:Immunophenotyping; D008213:Lymphocyte Activation; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000473:pathology*; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000473:pathology; D013602:T-Lymphocytes, Cytotoxic / Q000473:pathology
Bone marrow; Immune-checkpoint molecules; Multiple myeloma; T cell exhaustion; T cell senescence