Adoptive cell therapy of hematological malignancies using cytokine-induced killer cells retargeted with monoclonal antibodies

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Background & Aim Cytokine-Induced Killer (CIK) cells are a population of effector cells that represent a promising tool for adoptive cell therapy. From a technical and methodological point of view, they are easily expandable ex-vivo and safe, and demonstrated efficacy against hematological malignancies. CIK cells exert cytotoxicity against a broad range of tumor histotypes but not against normal tissues and hematopoietic precursors. We recently reported that they have a relevant expression of FcγRIIIa (CD16a), which can be exploited in combination with clinical-grade monoclonal antibodies (mAbs) to redirect their cytotoxicity in an antigen-specific manner, to improve their antitumor activity. Indeed, the engagement of CD16a on CIK cells leads to a potent antibody-dependent cell-mediated cytotoxicity (ADCC) against ovarian cancer both in vitro and in vivo. Based on this observation, we investigated whether CIK cells could be specifically retargeted against B-cell malignancies by combination with anti-CD20 mAbs, namely Rituximab® and Obinutuzumab®. Methods, Results & Conclusion CIK cells were obtained from peripheral blood mononucleated cells of healthy donors, and stimulated in vitro with IFN-γ, CD3 mAb (OKT3) and IL-2 for 14 days; fresh IL-2 was provided every 3-4 days. CIK cell phenotype was analyzed by multicolor flow cytometry; cytotoxic activity was assessed by calcein AM-release assay against EHEB (CLL), Raji (Burkitt lymphoma), RCK-8, TMB-8, Karpas 422 (DLBCL) tumor cell lines, and primary samples obtained from CLL and DLBCL patients after written informed consent. The combination with either the mAbs significantly increased CIK cell cytotoxicity not only against lymphoma cell lines, but also against the primary tumor samples. Depletion of NK cells from CIK cell bulk cultures did not affect target cell lysis, thus confirming that the antibody-mediated increase of cytotoxicity was mainly accountable to the CIK cell fraction. Taken together, these data indicate that the combination treatment with CIK cells and anti-CD20 mAbs could represent a novel approach for the treatment of hematological malignancies, alternative to the use of chimeric antigen receptor (CAR)-T cells.