Differentiation of CD8+ T cells from tumor-invaded and tumor-free lymph nodes of melanoma patients: Role of common γ-chain cytokines

Differentiation of CD8⁺ T cells at the tumor site toward effector and memory stages may represent a key step for the efficacy of antitumor response developing naturally or induced through immunotherapy. To address this issue, CD8⁺ T lymphocytes from tumor-invaded (n = 142) and tumor-free (n = 42) lymph nodes removed from the same nodal basin of melanoma patients were analyzed for the expression of CCR7, CD45RA, perforin, and granzyme B. By hierarchical cluster analysis, CD8⁺ T cells from all tumor-free lymph nodes and from 56% of the tumor-invaded lymph node samples fell in the same cluster, characterized mainly by CCR7⁺ CD45RA ^+/- cytotoxic factor-cells. The remaining three clusters contained only samples from tumor-invaded lymph nodes and showed a progressive shift of the CD8⁺ T cell population toward CCR7^- CD45RA ^-/+ perforin⁺ granzyme B⁺ differentiation stages. Distinct CD8⁺ T cell maturation stages, as defined by CCR7 vs CD45RA and by functional assays, were identified even in melanoma- or viral Ag-specific T cells from invaded lymph nodes by HLA tetramer analysis. Culture for 7 days of CCR7⁺ perforin^- CD8⁺ T cells from tumor-invaded lymph nodes with IL-2 or IL-15, but not IL-7, promoted, mainly in CCR7⁺CD45RA^- cells, proliferation coupled to differentiation to the CCR7^- perforin⁺ stage and acquisition of melanoma Ag-specific effector functions. Taken together, these results indicate that CD8⁺ T cells differentiated toward CCR7 ^- cytotoxic factor⁺ stages are present in tumor-invaded, but not in tumor-free, lymph nodes of a relevant fraction of melanoma patients and suggest that cytokines such as IL-2 and IL-15 may be exploited to promote Ag-independent maturation of anti-tumor CD8⁺ T cells.