Tumor-infiltrating CD39highCD8+ T cells exhibit a poor effector response and are associated to immunogenic tumors and hypoxic environments.

CANALE FP; BOSSIO SN; ABRATE C; GRUPPI A; ACOSTA RODRIGUEZ EV; MONTES CL

Congreso; Reunión Conjunta de Sociedades de Biociencias.; 2017

Previously we described that upregulation of the immunomodulatoryecto-enzyme CD39 on tumor-infiltrating CD8⁺ T lymphocytes(CD8+ TILs) is associated with an exhausted phenotype. Inthis work we aimed to better characterize the effector phenotype ofCD39⁺CD8⁺ TILs and their specific response against tumors. UsingB16F10-OVA mouse cancer model, we observed by FACS thatCD39highCD8+ TILs exhibited a higher frequency of KLRG-1⁺CD127-cells, a phenotype of short-live effector cells, than CD39lowCD8+TILs (p≤0,05). They also showed lower % of Ki-67⁺ cells (p≤0.05)and lower phosphorylation of mTOR and S6 (p≤0.05 for both) thanCD39lowCD8+ TILs, when re-stimulated in vitro. A high proportion ofCD39highCD8+ TILs were CD11a⁺CD49d⁺, a phenotype associatedwith antigenic stimulation. In accordance, when comparing the frequencyof CD39highCD8+ TILs between B16F10 and B16F10-OVAtumors we observed a significant higher percentage of these cellsin the latter (p≤0.01), indicating that higher immunogenicity promotesCD39 expression on CD8+ TILs. Studying OVA-specific CD8+TILs we observed that around 75% of these cells were CD39high.OVA-specific CD39highCD8+ TILs showed lower frequency of TNF⁺and IL-2⁺ cells, lower proliferative potential and higher inhibitoryreceptors expression than OVA-specific CD39lowCD8+ TILs (p≤0.05for all). Immunohistofluorescence of tumoral tissue showed thatCD39⁺CD45⁺ cells are accumulated in hypoxic foci. Moreover,CD39highCD8+ TILs showed higher binding to pimonidazole, a hypoxiamarker, than CD39lowCD8+ TILs. Our results demonstrate thatCD39 expression on CD8+ TILs is related to tumor immunogenicity.Moreover, high CD39 expression is associated to a dysfunctionalstate of antigen-specific CD8+ TILs. Interestingly, hypoxic environmentswithin tumors could promote CD39 expression. Consideringthe modulatory role of CD39, it emerges as a target for treatmentsaimed to restore CD8+ T cells anti-tumor immunity.CD8+ T cells, cancer, CD39, exhaustion, hypoxia.