Since cancer immunotherapy focuses on enhancing the anti-cancer capabilities of immune cells rather than killing cancer cells, one such potential approach of adoptive immunotherapy is cytokine-induced killer (CIK) therapy, which eliminates cancer cells by transfusing immune cells that have been expanded and activated in vitro. Phenotypically, CIK cells are heterogeneous in nature and composed of CD3+CD56− (T cells), CD3−CD56+ (NK cells), and CD3+CD56+ (NKT cells) cell populations
[4]. In fact, the CD3+CD56+ subset is considered as the major effector cells that exert potent anti-tumor cytotoxicity in a major histocompatibility complex (MHC)-unrestricted manner. The generation of CIK cells was first reported in 1991 by sequential incubation of peripheral blood mononuclear cells (PBMCs) with interferon-γ (IFN-γ), anti-CD3 monoclonal antibody (OKT3), and recombinant human interleukin-2 (rhIL-2)
[5]. The manufacturing process of autologous and allogeneic CIK cells is shown in
Figure 1.
Figure 1. Overview of multiple approaches aiming at improving cytokine-induced killer (CIK)cell therapy in lymphoma. Illustration showing the expansion of autologous or allogeneic CIK cells from PBMCs collected from the blood of lymphoma patients under incubation of IFN-γ, CD3 mAbs, and IL-2 for 2–3 weeks. To increase the cytotoxicity and specificity of CIK cells against lymphoma cells, several modifications are implemented.
Overview of multiple approaches aiming at improving cytokine-induced killer (CIK)cell therapy in lymphoma. Illustration showing the expansion of autologous or allogeneic CIK cells from PBMCs collected from the blood of lymphoma patients under incubation of IFN-γ, CD3 mAbs, and IL-2 for 2–3 weeks. To increase the cytotoxicity and specificity of CIK cells against lymphoma cells, several modifications are implemented.
Particularly, apparent differences can be drawn between CIK cells and the impressive immunologic approaches against lymphoma, including CAR-T and BiTE therapies (Particularly, apparent differences can be drawn between CIK cells and the impressive immunologic approaches against lymphoma, including CAR-T and BiTE therapies (
Table 1). Unlike CAR-T and BiTE that recognize tumor cells by targeting the tumor-associated antigens (TAAs), the majority of the CIK cell cytotoxicity results from the natural killer group 2 member D (NKG2D) interactions
[6][7][8][9]. NKG2D is expressed on all NK cells and recognizes at least six ligands that are relatively restricted on malignant tissues, including MHC class I-related molecules A and B (MICA and MICB) and members of the UL16-binding protein family (ULBP1-4)
[10]. The manufacturing of CAR-T cells requires genetic modification and cell expansion ex vivo, which is time-consuming and brings some financial considerations. However, the relative easiness of CIK cell preparation facilitates the fast growing of CIK cell therapy. Besides, cytokine release syndrome (CRS) is the most severe toxicity in CAR-T and BiTE therapies. It is associated with the rapid and extensive activation of T cells and the release of high-level proinflammatory cytokines (TNFα and IL-6)
[11]. Nonetheless, the crucial advantages of CIK cells are the relatively low toxicity and lack of graft-versus-host diseases (GVHD) response. The most common side effects in CIK cell therapy are fever, chills, fatigue, headache, and skin rash, and patients can usually recover with simple treatment
[12].
Table 1. Similarities and differences between CIK cells, CAR-T cells and BiTEs in lymphoma.
|
CIK Cells |
CAR-T Cells |
BiTEs |
Manufacturing Process |
PBMCs sequentially activated with 1000 IU/m IFN-γ on day 0, and 50 ng/mL anti-CD3 mAb and 600 IU/mL IL-2 on the following day; IL-2 supplemented every 2–3 days |
T cells with CAR gene transduction primarily by lentiviruses; CARs consist of an scFv based ectodomain for antigen-binding, a transmembrane domain, and an endodomain containing TCR CD3ζ chain with or without costimulatory signaling components |
Antibodies designed to bind to a selected TAA and CD3 on T cells simultaneously; produced in bioreactors by mammalian cell lines as secreted polypeptides |
Effector Cells |
CD3+CD56+ cells |
Mostly αβ-TCR+ T cells |
Endogenous CD8+ or CD4+ T cells |
Cell Source |
Autologous/allogeneic |
Autologous/allogeneic |
Autologous |
Target Antigen |
MIC A/B and ULBP1–4 |
CD19, CD20, CD22, CD30, BCMA, etc. |
CD19 |
MHC Restriction |
Dual-functional capability (non-MHC-restricted and TCR-mediated lysis) |
TAA recognition by CARs is MHC-unrestricted |
MHC-unrestricted |
Mechanism |
Release of perforin and granzyme B from CIK cells |
Release of perforin and granzyme B from CAR-T cells |
Activating T cells to release perforin and granzyme B by linking TAAs to CD3 on T cells |
Toxicities and Side effects |
Low-grade toxicities including fever, chills, fatigue, headache, and skin rash; grade 3 and 4 toxicities are rare; limited GVHD response in the allogeneic setting |
CRS, ICANS, and MAS/HLH; potentially life-threatening |
CRS and ICANS; severe toxicities are one of the major concerns |
Clinical Efficacy |
Varied due to heterogeneity of expension method and study design |
Axicabtagene ciloleucel: 83% ORR, 58% CR; Tisagenlecleucel: 54% ORR, 40% CR; Lisocabtagene maraleucel: 73% ORR, 53% CR | [13][14][15] |
Blinatumomab: 36% to 69% ORR in relapsed/refractory NHL | [16][17] |
CIK cells, cytokine-induced killer cells; MIC A/B, MHC class I-related molecules A and B; ULBP1–4, UL16-binding protein; GVHD, graft-versus-host diseases; CAR, chimeric antigen receptors; scFv, single-chain variable fragment; TCR, T cell receptor; TAA, tumor-associated antigen; CRS, cytokine release syndrome; ICANS, immune effector cell-associated neurotoxicity syndrome; MAS/HLH, Macrophage activation syndrome/hemophagocytic lymphohistiocytosis; CR, complete remission; ORR, objective response rate; BiTE, bispecific T cell engager.
3. Improving CIK Cell Therapy on Lymphoma
Despite the positive clinical benefit observed in trials, it is difficult to achieve long-lasting response and complete cancer eradication in patients with refractory or relapsed lymphoma. Therefore, a number of pre-clinical approaches are being investigated to improve CIK cell therapy to enhance its anti-tumor activity (
Figure 2). Among these innovative methods, bispecific antibodies (bsAb) represent a promising development bringing targeted antigen on tumor cells into close proximity to receptors on cytotoxic T-cells, and thereby triggering T-cell receptor signaling and anti-tumor immune response
[18]. In a particular study, it was reported that the bsAb CD19 × CD5 (HD37 × T5.16) enhanced the cytotoxicity activity of CIK cells against B lymphoma cells
[19]. Moore et al. used a bispecific antibody platform known as dual affinity retargeting (DART) to eradicate B-cell lymphomas by targeting the B-cell-specific antigen CD19 and the TCR/CD3 complex to effector T cells
[20]. Subsequently, it was shown that CIK cells and CD19xCD3 DART can control and/or eradicate patient-derived tumor xenografts from chemo-refractory B-ALL and diffuse large B-cell lymphoma (DLBCL) patients
[21].
Figure 2. Highlights in the development of CIK cell immunotherapy. In 1991, the development of CIK therapy began (in Germany) and continued in several countries, with 2011 being the year with the most clinical trial reports. The supporting pre-clinical models that are used to improve the therapeutic activity of CIK cells are also highlighted.
Likewise, studies also have shown an enhancement of CIK cell activity when combined with anti-CD20 antibodies. For instance, Pievani et al. showed that the addition of the anti-CD20 antibodies GA101 or rituximab in B-NHL increased the cytotoxicity of CIK cells by 35% and 15%, respectively
[22]. The authors also suggested that activation of the MAPK pathway may be a possible mechanism for the anti-apoptosis effect on CIK cell proliferation. Esser et al., investigated the effect of CIK cells in combination with brentuximab vedotin (SGN-35) on three different CD30+ lymphoma cell lines (Daudi, KI-JK, and L-540), and was found that the combined approach led to better results in vitro
[23]. Recently, a novel antibody-cell conjugation method for the enhancement and characterization of cytokine-induced killer cells has been presented
[24]. The authors demonstrated that CIK cells conjugated with rituximab exhibited increased cytotoxic activity against CD20+ lymphoma cell lines and suggested that without any genetic modification, CIK cells can be rapidly equipped with monoclonal antibodies to target tumor cells.
Biederbick et al. recently contributed to raise concerns about synergistic molecular mechanisms of CIK cells by using a combination of anti-CD40 and anti-GITR mAb in the human lymphoma cell lines SU-DHL-4 and Daudi (both CD40-positive)
[25]. More recently, Li et al. reported an increase in IFN-γ secretion in B-NHL cell lines treated with CIK alone or with the PD-1 antibody, yet this trend was not observed for PD-L1, raising the question of whether PD-1 and PD-L1 are comparable and interchangeable in the clinical practice
[26].
.