Up-regulation of inhibitory natural killer receptors CD94/NKG2A with suppressed intracellular perforin expression of tumor-infiltrating CD8 ⁺ T lymphocytes in human cervical carcinoma

Inhibitory signals that govern the cytolytic functions of CD8 + T lymphocytes have been linked to the expression of natural killer cell receptors (NKRs) on CTLs. There is limited knowledge about the induction of inhibitory NKR (iNKR) expression in vivo. Up-regulation of iNKRs has been linked to the modulation of the virus- and/or tumor-specific immune responses in animal models. In the present study, we directly examined the expression of various NKRs on tumor-infiltrating lymphocytes (TILs) derived from human cervical cancer. We found that in human cervical cancer, the percentage expression of immunoglobulin-like NKR + CD8 + T lymphocytes were similar in gated CD8 + -autologous TILs and peripheral blood mononuclear cells. On the contrary, cervical cancer-infiltrating CD8 + T lymphocytes expressed up-regulated C-type lectin NKRs CD94/NKG2A compared with either peripheral blood CD8 + T cells or normal cervix-infiltrating CD8 + T lymphocytes. Dual NKR coexpression analyses showed that CD94 and NKG2A were mainly expressed on CD56 - CD161 - CD8 + TILs within the cancer milieu. Immunohistochemical study showed that cervical cancer cells expressed abundant interleukin 15 (IL-15) and transforming growth factor-β (TGF-β). In kinetic coculture assay, cervical cancer cells can promote the expression of CD94/NKG2A on CD8 + T lymphocytes. The cancer-derived effects can be reversed by addition of rIL-15Rα/Fc and anti-TGF-β antibody. Functional analyses illustrated that intracellular perforin expression of CD8 + T cells was minimal upon up-regulation of CD94/NKG2A. Kinetic cytotoxicity assays showed that up-regulated expressions of CD94/NKG2A restrain CD8 + T lymphocyte cytotoxicity. Our study strongly indicated that cervical cancer cells could promote the expression of iNKRs via an IL-15- and possibly TGF-β-mediated mechanism and abrogate the antitumor cytotoxicity of TILs.