Increased frequency of TIGIT+CD73-CD8+ T cells with a TOX+ TCF-1low profile in patients with newly diagnosed and relapsed AML

The inhibitory receptor TIGIT, as well as theectonucleotidases CD39 and CD73 constitute potential exhaustion markers for T cells. Detailed analysis of these markers can shed light into dysregulation of the T-cell response in acute myeloid leukemia (AML) and will help to identify potential therapeutic targets. The phenotype and expression of transcription factors was assessed on different T-cell populations derived from peripheral blood (PB, n = 38) and bone marrow (BM, n = 43). PB and BM from patients with AML diagnosis, in remission and at relapse were compared with PB from healthy volunteers (HD) (n = 12) using multiparameter flow cytometry. An increased frequency of terminally differentiated (CD45R(-)CCR7(-))CD8(+) T cells was detected in PB and BM regardless of the disease state. Moreover, we detected an increased frequency of two distinct T-cell populations characterized by the co-expression of PD-1 or CD39 on TIGIT(+)CD73(-)CD8(+) T cells in newly diagnosed and relapsed AML in comparison to HDs. In contrast to the PD-1(+)TIGIT(+)CD73(-)CD8(+) T-cell population, the frequency of CD39(+)TIGIT(+)CD73(-)CD8(+) T cells was normalized in remission. PD-1(+)- and CD39(+)TIGIT(+)CD73(-)CD8(+) T cells exhibited additional features of exhaustion by decreased expression of CD127 and TCF-1 and increased intracellular expression of the transcription factor TOX. CD8(+) T cells in AML exhibit a key signature of two subpopulations, PD-1(+)TOX(+)TIGIT(+)CD73(-)CD8(+)- and CD39(+)TOX(+)TIGIT(+)CD73(-)CD8(+) T cells that were increased at different stages of the disease. These results provide a rationale to analyze TIGIT blockade in combination with inhibition of the purinergic signaling and depletion of TOX to improve T-cell mediated cytotoxicity in AML.