Pretherapy predictive immunomodulation of NK cell activity and expression of activating and inhibitory receptors in stage IV melanoma patients

Abstract

12514 Background: As melanoma (MM) is an immunogenic tumor with poor response to chemotherapy immunomodulating agents are applied in order to potentiate cytotoxic effect of chemotherapy and enhance antitumor immune response. Beside therapeutic benefit of IFN-α and IL-2, 13-cis retinoic acid (RA), as an antiproliferative, differentiating and immunomodulating agent is also investigated. The effect of these agents on NK cells, as main innate immune system effectors, is being investigated. Methods: 35 patients with MM in stage IV prior to therapy and 20 controls were investigated. We evaluated NK activity and the expression of activating (NKG2D and CD161) and inhibitory (CD158a and CD158b) receptors on freshly isolated PBL. Predicitive immunomodulation was performed in 18 h in vitro treated PBL with rh IL-2 (200U/ml), IFN (250U/ml), RA (10−6M), and their combination. Results: Native NK cell cytotoxic activity and expression of NKG2D and CD161 activating receptors on fresh NK cells in MM patients is significantly decreased compared to controls. Predictive treatments with IL-2, IFN, IFN and RA, unlike RA alone, gave a significant increase in NK cell activity of MM patients. Singly, IFN also induced a significant increase in CD161 expression on NK cells in patients. The treatments gave no change in the expression of CD158b, while RA, alone, induced significant decrease in the expression of the inhibitory CD158a antigen. Evaluation of mRNA of transcription molecule IRF-1 shows that it is promptly up-regulated by IFNα, more by IFNα and RA, while single RA has no effect on mRNA induction. Conclusions: Considering that the mechanism of applied immunomodulating agents is continually investigated in order to optimize the dose and schedule of their administration and, also, considering controversial clinical results of RA application, alone, or with IFN, in this study we give novel results that show no significant effect of RA, whereas, IFN-induced increase in NK cell activity of MM patients is for the first time associated with the increase in the expression of NKG2D and CD161 receptors on CD16+NK cells, and not with the decrease in some inhibitory receptors, as the activity of NK cells is regulated by the balance of these two types of signals. No significant financial relationships to disclose.