In vitro increased natural killer cell activity of metastatic melanoma patients with interferon-alpha alone as opposed to its combination with 13-cis retinoic acid is associated with modulation of NKG2D and CD161 activating receptor expression

Abstract

Purpose: Considering tumor-induced suppression of natural killer (NK) cell activity the aim of this study was to investigate the in vitro effect of a standard immunotherapeutic cytokine, interferon (IFN)α, and a less investigated agent, 13-cis retinoic acid (RA) on the functional and receptor characteristics of CD16-defined NK cells and their functionally diverse dim and bright subsets in patients with metastatic melanoma (MM). Methods: Peripheral blood lymphocytes (PBL) of patients with clinical stage IV MM were stimulated in vitro for 18 h in RPMI 1640 culture medium (CM) alone, CM supplemented with IFN-α (250 U/ml), RA (10-6M) and their combination. NK cell activity was determined using standard 4 h radioactive cytotoxicity assay, while the expression of activating (NKG2D, CD161) and inhibitory (CD158a, CD 158b) NK cell receptors on CD3- CD16+ NK cells and their functional bright and dim subsets were analyzed by flow cytometry. Results: NK cell cytotoxic activity was increased after in vitro treatment with IFN-α alone and in combination with RA, while only IFN-α induced increase in NKG2D and CD161 activating NK cell receptor expression. Contrary to this, RA treatment increased the expression of inhibitory KIR CD158b. IFN-α-obtained increase in CD161 expression was due to its induction on both NK cell subsets, while for NKG2D only on CD16bright subset. Conclusion: The favorable enhancement of NK cell activity of MM patients obtained with IFN-α is associated with upregulation of activating NKG2D and CD161 receptors, while the lack of RA-associated upregulation is probably due to the shown increased expression of inhibitory KIR receptor CD158b after in vitro treatment with this agent. © 2012 Zerbinis Medical Publications.