N-acetylcysteine potentiates the tumor cytotoxicity of cytokine-induced killer cells

Pornpimon Ek-eudomsuk, Chonvara Chalermrujinanant, Kitipong Soontrapa

Department of Pharmacology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand

Abstract

Background: Cytokine-induced killer (CIK) cells are an ex vivo expanded heterogeneous population of natural killer (NK)-like T cells that can exert potent MHC-unrestricted antitumor activity. A number of pre-clinical and clinical studies have demonstrated that CIK cells can serve as a safe and potent immunotherapy of malignant tumors. N-acetylcysteine (NAC) has been demonstrated to enhance the T-cell functions by increasing their proliferation and cytokine production.
Objective: To investigate whether the incorporation of NAC to CIK cell culture could enhance the antitumor activity of CIK cells.
Methods: The phenotypes of human CIK cells, including CD3⁺CD56⁺, IFN-γ, granzyme B, and perforin, were determined by flow cytometry. The cytotoxic activity against the human erythroleukemic cell line (K562) and cholangiocarcinoma cell line (CL6) prelabeled with CFSE was investigated by flow cytometry. The mRNA expression levels of IFNG, PRF1, and GZMB were measured by real-time PCR.
Results: By adding NAC into CIK cell culture, the percentage of CD3⁺CD56⁺ cells along with the expression of Th1 cytokines and cytolytic granules increased significantly, resulting in an improvement of cytotoxicity against the cancer cell lines CL6 and K562.
Conclusions: The incorporation of NAC into CIK culture can markedly improve the cytotoxicity against cancer cells due to the significant increase in the major effector population of CIK cells expressing Th1 cytokines and cytolytic granules.
Key words: Cytokine-induced killer cells, N-acetylcysteine, Cancer immunotherapy, Cytotoxicity, Antitumor effect