Contributions
Abstract: EP410
Type: E-Poster Presentation
Session title: Acute myeloid leukemia - Biology & Translational Research
Background
The inhibitory receptor TIGIT, as well as the ectonucleotidases CD39 and CD73 constitute potential exhaustion markers for T cells. Detailed analysis of these markers may shed light into dysregulation of the T-cell response in acute myeloid leukemia (AML) and help to identify potential therapeutic targets.
Aims
In the current study we analyzed multiple inhibitory receptors and members of the purinergic system which have also been involved into downregulation of T-cell effector function aiming to identify relevant new pathways of T-cell mediated immune failure in AML.
Methods
The differentiation state, phenotype and expression of transcription factors was assessed on T cells derived from peripheral blood (PB n=38) and bone marrow (BM n=43). PB and BM collected from patients with newly diagnosed primary AML, at relapse after intensive chemotherapy and in remission were compared to healthy volunteers (HD n=12). The surface expression of PD-1, TIGIT, CD73, and CD39, as well as of the differentiation markers CD45RO, CCR7, CD25 and CD127 were determined on CD8+and conventional and regulatory CD4+T (CD4+CD127-CD25hi)cells using multiparameter flow cytometry.
Results
An increased frequency of terminally differentiated (CD45R-CCR7-) CD8+ T cells was confirmed in the PB and BM regardless of the AML disease status (p<0,05). Moreover, CD39 was aberrantly expressed on this population: we observed an increased frequency of CD39+TIGIT+CD73-CD8+ T cells in PB from patients with newly diagnosed AML and relapsed AML compared to PB from HDs (13,47 ± 4,03 vs. 15,8 ± 3,04 vs. 3,03 ± 1,21; p<0.05; p<0.01). For analysis of the functional relevance of the CD39+TIGIT+CD73-CD8+ T cells mononuclear cells of the PB (PBMC) from HDs were pre-incubated with inhibitors against TIGIT (50µg/ml) and CD39 (50µg/ml) and co-cultured with either AML OCI-3 or OCI-5 cells (E:T Ratio 6:1, n=3). After 24 hours of co-culture lysis of AML cells was assessed by flow cytometry. Treatment of anti-TIGIT, anti-CD39 or the combinatorial inhibition significantly increased T-cell mediated lysis of AML cells (lysis of AML OCI-3 cells measured by fold change: anti-CD39 1,53; anti-TIGIT 2,22 ; anti-CD39 + anti-TIGIT 2,67 and lysis of AML OCI-5 cells: anti-CD39 2,21; anti-TIGIT 1,63 ; anti-CD39 + anti-TIGIT 2,81).
Conclusion
CD8+ T cells in the PB and BM from patients with AML exhibit a key signature of CD39+TIGIT+CD73-CD8+ T cells that were specifically increased at different stages of the disease. Through inhibition of CD39 in combination with TIGIT T-cell mediated lysis could be increased in AML. These results provide a rationale to further evaluate the TIGIT checkpoint blockade in combination with inhibition of the purinergic signaling to improve T-cell mediated cytotoxicity in AML.
Keyword(s): AML, CD8 T cells, Immune therapy
Abstract: EP410
Type: E-Poster Presentation
Session title: Acute myeloid leukemia - Biology & Translational Research
Background
The inhibitory receptor TIGIT, as well as the ectonucleotidases CD39 and CD73 constitute potential exhaustion markers for T cells. Detailed analysis of these markers may shed light into dysregulation of the T-cell response in acute myeloid leukemia (AML) and help to identify potential therapeutic targets.
Aims
In the current study we analyzed multiple inhibitory receptors and members of the purinergic system which have also been involved into downregulation of T-cell effector function aiming to identify relevant new pathways of T-cell mediated immune failure in AML.
Methods
The differentiation state, phenotype and expression of transcription factors was assessed on T cells derived from peripheral blood (PB n=38) and bone marrow (BM n=43). PB and BM collected from patients with newly diagnosed primary AML, at relapse after intensive chemotherapy and in remission were compared to healthy volunteers (HD n=12). The surface expression of PD-1, TIGIT, CD73, and CD39, as well as of the differentiation markers CD45RO, CCR7, CD25 and CD127 were determined on CD8+and conventional and regulatory CD4+T (CD4+CD127-CD25hi)cells using multiparameter flow cytometry.
Results
An increased frequency of terminally differentiated (CD45R-CCR7-) CD8+ T cells was confirmed in the PB and BM regardless of the AML disease status (p<0,05). Moreover, CD39 was aberrantly expressed on this population: we observed an increased frequency of CD39+TIGIT+CD73-CD8+ T cells in PB from patients with newly diagnosed AML and relapsed AML compared to PB from HDs (13,47 ± 4,03 vs. 15,8 ± 3,04 vs. 3,03 ± 1,21; p<0.05; p<0.01). For analysis of the functional relevance of the CD39+TIGIT+CD73-CD8+ T cells mononuclear cells of the PB (PBMC) from HDs were pre-incubated with inhibitors against TIGIT (50µg/ml) and CD39 (50µg/ml) and co-cultured with either AML OCI-3 or OCI-5 cells (E:T Ratio 6:1, n=3). After 24 hours of co-culture lysis of AML cells was assessed by flow cytometry. Treatment of anti-TIGIT, anti-CD39 or the combinatorial inhibition significantly increased T-cell mediated lysis of AML cells (lysis of AML OCI-3 cells measured by fold change: anti-CD39 1,53; anti-TIGIT 2,22 ; anti-CD39 + anti-TIGIT 2,67 and lysis of AML OCI-5 cells: anti-CD39 2,21; anti-TIGIT 1,63 ; anti-CD39 + anti-TIGIT 2,81).
Conclusion
CD8+ T cells in the PB and BM from patients with AML exhibit a key signature of CD39+TIGIT+CD73-CD8+ T cells that were specifically increased at different stages of the disease. Through inhibition of CD39 in combination with TIGIT T-cell mediated lysis could be increased in AML. These results provide a rationale to further evaluate the TIGIT checkpoint blockade in combination with inhibition of the purinergic signaling to improve T-cell mediated cytotoxicity in AML.
Keyword(s): AML, CD8 T cells, Immune therapy