CD39 delineates cell exhaustion in mouse and human tumor-associated CD8+ T cells: a possible immunomodulatory role of a ?dysfunctional? cell subset

FP CANALE; MC RAMELLO; N NÚÑEZ; CL ARAUJO FURLAN; M GOROSITO SERRÁN; J TOSELLO BOARI; SN BOSSIO; A DEL CASTILLO; M LEDESMA; C SEDLIK; E PIAGGIO; A GRUPPI; EV ACOSTA RODRIGUEZ; CL MONTES

Mar del Plata

Congreso; LXIV Reunión Anual de la Sociedad Argentina de Inmunología (SAI); 2016

Tumor-infiltrating CD8+ T lymphocytes (CD8+ TILs) are crucial to eliminate tumors through cytotoxicity and cytokine production. Cancer cells blunt this process developing a microenvironment that induces dysfunctional and regulatory T cells. Here, we aimed to study by flow cytometry the expression of the immunomodulatory ecto-enzyme CD39 on CD8+ T cells in the context of anti-tumorresponse. Studying B16F10-OVA and other mouse cancer models, we defined three subsets: CD39-, CD39int and CD39high CD8+ T cells, being the latter predominant in tumors but absent in lymphoid organs (p≤0.0001). Of note, the frequency of CD39high CD8+ TILs increased with tumor growth (p≤0.0001). CD39high CD8+TILs exhibited an exhausted phenotype with lower production of TNF (p≤0.001) and IL-2 (p≤0.01) than CD39-/CD39int CD8+ TILs, and higher expression of inhibitory receptors (PD-1, Tim-3, LAG-3, TIGIT and 2B4) (p≤0.0001 for all). Murine exhausted CD8+ T cells displayed high ability to hydrolyze extracellular ATPin vitro, indicating that CD39 is enzymatically active on these cells. Moreover, co-culture experiments showed that exhausted CD8+ TILs are able to reduce IFNã production by conventional CD8+ T cells (p≤0.05). Interestingly, in samples from 29 breast cancer and 4 melanoma patients we observed that CD39+ CD8+ T cells were present in tumors and increased in invaded/metastatic lymph nodes compared to non-invaded lymph nodes (p≤0.001), while absent in peripheral blood. These cells exhibited impaired production of IFNã (p≤0.001), TNF (p≤0.01) and IL-2 (p≤0.05 in lymph nodes) when compared to CD39- CD8+ T cells, and higher expression of PD-1 (p≤0.01), TIGIT (p≤0.01) and BTLA (p≤0.05). These findings suggest that beside the loss of effector functions, the tumor environment also drives the acquisition of regulatory molecules on CD8+ T cells. CD39 may emerge not only as a marker of CD8+ T cell dysfunction but also as a possible target for treatments aimed to restore anti-tumor immunity.