Promising immunotherapy: Highlighting cytokine-induced killer cells

For many years, cancer therapy has appeared to be a challenging issue for researchers and physicians. By the introduction of novel methods in immunotherapy, the prospect of cancer therapy even more explained than before. Cytokine-induced killer (CIK) cell-based immunotherapy demonstrated to have potentiality in improving clinical outcomes and relieving major side effects of standard treatment options. In addition, given the distinctive features such as high safety, low toxicity effects on healthy cells, numerous clinical trials conducted on CIK cells. Due to the shortcomings that observed in CIK cell immunotherapy alone, arising a tendency to make modifications (combined modality therapy or combination therapy) including the addition of various types of cytokines, genetic engineering, combination with immune checkpoints, and so on. In this review, we have tried to bring forth the latest immunotherapy methods and their overview. We have discussed the combination therapies with CIK cells and the conducted clinical trials. This helps the future studies to use integrated therapies with CIK cells as a promising treatment of many types of cancers.     

Efficacy of adjuvant immunotherapy with cytokine-induced killer cells in patients with locally advanced gastric cancer

Purpose

To determine the long-term efficacy of adjuvant immunotherapy with autologous cytokine-induced killer (CIK) cells for locally advanced gastric cancer patients.

Experimental design

One hundred and fifty-one patients with stage III/IV gastric cancer who had undergone gastrectomy were enrolled, assigned to two groups (immunotherapy group versus no immunotherapy group/or control group), and followed.

Results

The 5-year overall survival (OS) and 5-year disease-free survival (DFS) rates for immunotherapy versus control group were 32.4 versus 23.4?% (P?=?0.071) and 28.3 versus 10.4?% (P?=?0.044), respectively. For patients with intestinal-type tumors, the 5-year OS and DFS rates were significantly higher for immunotherapy (OS, 46.8 vs. 31.4?% and P?=?0.045; DFS, 42.4 vs. 15.7?% and P?=?0.023). In the immunotherapy group, the mean CD3⁺ level, CD4⁺ level, and CD4⁺/CD8⁺ ratio increased from 50.8, 26.5, and 0.9?%, respectively, at baseline to 62.6, 35.0, and 1.4?%, respectively, 1?week after the first CIK-cell treatment, returned to baseline after 2?months, and maintained a higher level (60.7?±?8.2?%, 34.2?±?7.1?%, and 1.3?±?0.3?%, respectively) 2?months after 3 cycles of immunotherapy.

Conclusions

Adjuvant immunotherapy with CIK cells prolongs DFS in patients with locally advanced gastric cancer and significantly improves OS in patients with intestinal-type tumors. Intestinal-type tumors could be selected as an important indication for CIK-cell therapy. This treatment may help improve T-lymphocyte subset distribution and improve the host??s immune functions, but multiple cycles are necessary for long-term therapeutic efficacy.     

Ten-year update of the international registry on cytokine-induced killer cells in cancer immunotherapy

Cytokine-induced killer (CIK) cells represent an exceptional T-cell population uniting a T cell and natural killer cell-like phenotype in their terminally differentiated CD3⁺CD56⁺ subset, which features non-MHC-restricted tumor-killing activity. CIK cells have provided encouraging results in initial clinical studies and revealed synergistic antitumor effects when combined with standard therapeutic procedures. We established the international registry on CIK cells (IRCC) to collect and evaluate clinical trials for the treatment of cancer patients in 2010. Moreover, our registry set new standards on the reporting of results from clinical trials using CIK cells. In the present update, a total of 106 clinical trials including 10,225 patients were enrolled in IRCC, of which 4,889 patients in over 30 distinct tumor entities were treated with CIK cells alone or in combination with conventional or novel therapies. Significantly improved median progression-free survival and overall survival were shown in 27 trials, and 9 trials reported a significantly increased 5-year survival rate. Mild adverse effects and graft-versus-host diseases were also observed in the studies. Recently, more efforts have been put into the improvement of antitumoral efficacy by CIK cells including the administration of immune checkpoint inhibitors and modification with chimeric antigen receptorc. The minimal toxicity and multiple improvements on their tumor-killing activity both make CIK cells a favorable therapeutic tool in the clinical practice of cancer immunotherapy.     

Cancellous bone allograft seeded with human mesenchymal stromal cells: a potential good manufacturing practice-grade tool for the regeneration of bone defects

Background aimsCombining autologous bone precursor cells with cancellous bone allograft (CBA) offers an appealing strategy for skeletal regeneration. In this context, multipotent mesenchymal stromal cells (MSC) provide an excellent cell source because they are readily harvested from donors, expanded and differentiated in vitro. The aim of this study was to evaluate the proliferation, morphology, osteogenic differentiation and stem cell-related gene expression during static long-term ex vivo cultivation using human MSC and CBA under good manufacturing practice (GMP)-conforming conditions.MethodsMSC were isolated from healthy donors (n = 5) and cultivated on peracetic acid-sterilized CBA in the presence of 10% human platelet-rich plasma without osteogenic supplements. Total protein content, cell-specific alkaline phosphatase (ALP) activity and osteogenic marker gene expression levels were assessed. Stem cell-related gene expression was compared with MSC monolayer cultivation using microarray analysis. Furthermore, cellular distribution and morphology within the porous CBA were visualized by histology and scanning electron microscopy.ResultsEffective adhesion, spreading, proliferation and intercellular contact of human MSC within the pores of CBA were observed during the study (≤42 days). Cell-specific ALP activity peaked after 3 weeks of cultivation. Gene expression of early, intermediate and late osteogenic marker genes was detectable during long-term cultivation. Microarray-based annotation and biologic interaction network data analysis indicated that expression levels of genes encoding crucial differentiation-regulating proteins and extracellular matrix components involved in the process of osteogenesis were induced in CBA-cultivated MSC.ConclusionsMSC-vitalized CBA offers an attractive GMP-grade bone-filling material. Further research is warranted to evaluate its bone-healing potential in vivo.     

Adoptive immunotherapy of a mouse colon carcinoma with recombinant interleukin-2 alone or combined with lymphokine-activated killer cells or tumor-immune lymphocytes

Summary We have used a BALB/c colonic adenocarcinoma (C-26) to evaluate the therapeutic potential of recombinant interleukin-2 (rIL-2) at high and low dosages in combination with or without lymphokine-activated killers (LAK) or tumor-specific, immune lymphocytes in either an adjuvant spontaneous or an artificial metastasis system. Most (80%) of the mice that underwent s.c. C-26 tumor excision were shown to die of spontaneous metastasis with lung involvement by 1–4 months after excision. Postsurgical systemic treatment with low-dose rIL-2 (3 × 10⁴ U/day, i.p.) increased the survival rate to 31% as compared to 21% (not significant) in excised controls while administration of high-dose rIL-2 (8 × 10⁴ U/day) led to 53% survival (P <0.01). Both LAK cells and C-26-tumor-immune lymphocytes given during rIL-2 treatment significantly increased the effects of rIL-2 at the low but not at the high-dose, with tumor-immune effectors resulting in the highest percentage (63%) of cures. When mice bearing 3-day artificial lung metastases of C-26 cells were treated with low- or high-dose rIL-2, in combination with or without LAK or tumor-immune lymphocytes, a highly significant reduction or abrogation of the number of lung foci was observed with all treatments, including those involving or tumor-immune lymphocytes alone. Assessment of survival benefit in these mice, however, showed survival prolongation, with 20% cures achieved by low-dose rIL-2 alone and up to 65% cures by LAK in combination with low-dose rIL-2. In this system of artificial metastasis high-dose rIL-2 alone increased the survival time but failed to cure the animals, and the addition of LAK was ineffective whereas that of tumor-immune lymphocytes led to 80% cure. These results suggest that tumorimmune lymphocytes are more effective than LAK when combined with rIL-2 and that caution is necessary in extrapolating findings obtained in artificial metastasis models.     

Treatment of multiple solitary plasmacytomas with cytokine-induced killer cells

Background aimsCurrently available treatment methods for advanced plasmacytoma include surgery, chemotherapy, radiotherapy, immunomodulatory agents, hematopoietic stem cell transplantation and donor lymphocyte infusion. We report a case of advanced refractory multiple solitary plasmacytomas in a 68-year-old Asian man with multiple bone lesions, in whom autologous cytokine-induced killer (CIK) cells were administered in an effort to eliminate residual tumor lesions.MethodsCIK cells were infused monthly for 21 courses.ResultsThe patient has survived 63 months since the first hospital visit without disease progression for 40 months.ConclusionsThis case represents the first report of autologous CIK cell immunotherapy used successfully to suppress multiple solitary plasmacytomas and resolve bone lesions.     

Autologous cytokine-induced killer cell immunotherapy in lung cancer: a phase II clinical study

Objective

Cytokine-induced killer (CIK) cells have the ability to kill tumor in vitro and in vivo. This study was designed to evaluate the clinical efficacy of CIK cell immunotherapy following regular chemotherapy in patients with non-small cell lung cancer (NSCLC) after surgery.

Methods

A paired study, with 87 stage I–IV NSCLC patients in each group, was performed. Patients received either chemotherapy (arm 2) or chemotherapy in combination with autologous CIK cell immunotherapy (arm 1). Progression-free survival (PFS) and overall survival (OS) were evaluated.

Results

Of the 87 paired patients, 50 had early-stage disease (stage I–IIIA) and 37 had advanced-stage disease (stage IIIB–IV). Among early-stage patients, the distribution of 3-year PFS rate and median PFS time showed no statistical difference between the two groups (p = 0.259 and 0.093, respectively); however, the 3-year OS rate and median OS time in arm 1 were significantly higher than those in arm 2 (82 vs. 66 %; p = 0.049 and 73 vs. 53 months; p = 0.006, respectively). Among the advanced-stage patients, the 3-year PFS and OS rates of arm 1 were significantly higher than those of arm 2 (6 vs. 3 %; p < 0.001 and 31 vs. 3 %; p < 0.001, respectively); the median PFS and OS times in arm 1 were also significantly longer than those in arm 2 (13 vs. 6 months; p = 0.001 and 24 vs. 10 months; p < 0.001, respectively). Multivariate analyses indicated that the frequency of CIK cell immunotherapy was significantly associated with prolonged PFS (HR = 0.91; 95 % CI 0.85–0.98; p = 0.012) and OS (HR = 0.83; 95 % CI, 0.74–0.93; p = 0.001) in the arm 1.

Conclusions

The data suggested that CIK cell immunotherapy could improve the efficacy of conventional chemotherapy in NSCLC patients, and increased frequency of CIK cell treatment could further enhance the beneficial effects. A multi-center randomized trial is being carried out in our hospital to further validate these findings.     

自体CIK细胞治疗21例中晚期恶性实体瘤的肿瘤标志物变化观察

目的观察自体细胞因子诱导的杀伤细胞（CIK）过继免疫疗法治疗中晚期恶性实体肿瘤的临床疗效及肿瘤标志物变化,初步对该疗法作出评价。方法取中晚期恶性实体肿瘤患者自体外周血50ml,根据文献报道方法体外诱导扩增CIK细胞。培养约14d后,一次性回输入患者体内,观察患者CIK细胞回输前2周及回输后4周左右外周血免疫指标变化、肿瘤标志物变化、生活质量及Karnofsky评分变化,随访1年观察1年生存率。采用t检验及寿命表法进行统计分析。结果在21例接受CIK回输治疗的患者中,治疗前出现有代表意义的肿瘤标志物异常升高的患者有14例,1次回输后有8名患者出现肿瘤标志物下降,其中1名患者降至正常范围;免疫指标在CIK细胞回输后4周较回输前2周均无有统计学意义,其中CD3由70.81﹪±10.52﹪升至71.91﹪±11.09﹪,t=0.762,P=0.455;CD4由39.06﹪±11.03﹪升至39.21﹪±8.74﹪,t=0.093,P=0.927;CD8由28.75﹪±8.22﹪升至29.88﹪±10.13﹪,t=0.895,P=0.382;CD16^＋CD56^＋（即NK细胞）由15.73﹪±9.52﹪升至15.37﹪±6.66﹪,t=-0.173,P=0.865;EORTCQLQ-C30（vertion3.0）评分中总体健康状况（globalhealth）由（41.67±17.28）分上升至（46.43±17.19）分,P=0.076;以上各指标治疗前后差异均无统计学意义。但功能子量表中的躯体功能（physicalfunctioning）单项[由（62.94±17.48）分上升至（66.67±17.37）分,P=0.012]和症状子量表中的疲倦（fatigue）[由（51.33±20.03）分下降至（43.38±16.81）分,P=0.012]、疼痛（pain）[由44.44﹪±19.24﹪下降至（36.51±14.55）分,P=0.038]及食欲丧失（appetiteloss）[由（52.38±19.92）分下降至（38.09±21.82）分,P=0.016]单项差异均有统计学意义（P〈0.05）;卡氏评分由[（61.42±3.59）分上升至（62.38±4.36）分,t=1.000,P〉0.05];随访1年内有3名患者死亡,生存率约85.7﹪。结论自体CIK细胞回输治疗后肿瘤标志物有明显改变,同时对缓解晚期恶?     

IL-12 enhances efficacy and shortens enrichment time in cytokine-induced killer cell immunotherapy

Cytokine-induced killer (CIK) cells are T cell derived ex vivo expanded cells with both NK and T cell properties. They exhibit potent anti-tumor efficacy against various malignancies in preclinical models and have proven safe and effective in clinical studies. We combined CIK cell adoptive immunotherapy with IL-12 cytokine immunotherapy in an immunocompetent preclinical breast cancer model. Combining CIK cells with IL-12 increased anti-tumor efficacy in vivo compared to either therapy alone. Combination led to full tumor remission and long-term protection in 75% of animals. IL-12 treatment sharply increased the anti-tumor efficacy of short-term cultured CIK cells that exhibited no therapeutic effect alone. Bioluminescence imaging based in vitro cytotoxicity and in vivo homing assays revealed that short-term cultured CIK cells exhibit full cytotoxicity in vitro, but display different tumor homing properties than fully expanded CIK cells in vivo. Our data suggest that short-term cultured CIK cells can be “educated” in vivo, producing fully expanded CIK cells upon IL-12 administration with anti-tumor efficacy in a mouse model. Our findings demonstrate the potential to improve current CIK cell-based immunotherapy by increasing efficacy and shortening ex vivo expansion time. This holds promise for a highly efficacious cancer therapy utilizing synergistic effects of cytokine and cellular immunotherapy.     

Cancer immunotherapy with interleukin-2-activated natural killer cells

Natural killer (NK) cells are a subset of lymphocytes with a distinct morphologic appearance (large granular lymphocytes [LGL]) and the ability to kill virally infected and tumor targets but to spare most normal cells. NK cells respond to a variety of biologic agents, such as interleukin-2 (IL-2), or interferons, by upregulation of cytolytic, secretory, and proliferative functions. In cancer-bearing hosts, NK cells have been considered to be the major component of antitumor immunity responsible for rapid elimination of malignant cells from the blood. More recently, however, studies have demonstrated the ability of adoptively transferred, IL-2-activated NK cells to selectively localize into solid tumors tissue and to eliminate established tumors. While these findings indicate a role for NK cells in cancer immunotherapy, additional studies are needed in both animal models and in humans to optimize clinical protocols of cancer therapy based on these cells.     

Long-term clinical efficacy of cytokine-induced killer cell-based immunotherapy in early-stage esophageal squamous cell carcinoma

Background aimsIn this retrospective clinical study, the authors investigated the impact of cytokine-induced killer (CIK) cell-based immunotherapies on the long-term survival of patients with esophageal squamous cell carcinoma (ESCC).MethodsA total of 87 patients with ESCC who received comprehensive treatment were enrolled in the study. Of these patients, 43 were in the control group and 44 were in the CIK treatment group. Flow cytometry analysis was performed to detect the phenotype and anti-tumor function of CIK cells. Clinical characteristics were compared between these two groups, and the survival estimates of ESCC patients were determined using Kaplan–Meier analysis.ResultsCIK cells contained a high proportion of the main functional fraction (CD3⁺CD56⁺ group) and exhibited a strong killing ability for esophageal cancer cells in vitro. Importantly, overall survival (OS) and progression-free survival (PFS) were significantly higher in the CIK group than in the control group in early-stage ESCC. However, patients with advanced-stage ESCC did not benefit from CIK cell-based therapy in terms of OS and PFS compared with the control group.ConclusionsThese results demonstrate that CIK cells combined with conventional treatments potentially prolong long-term survival of patients and may serve as a combined therapeutic approach for the treatment of early-stage ESCC.     

Immunomagnetic selection or irradiation eliminates alloreactive cells but also reduces anti-tumor potential of cytokine-induced killer cells: implications for unmanipulated cytokine-induced killer cell infusion

Background aimsCytokine-induced killer (CIK) cells may offer a novel therapeutic approach for patients with malignancies relapsing after allogeneic stem cell transplantation. Although CIK cells display negligible alloreactivity and cause minimal graft versus-host-disease (GVHD), high CIK cell doses required during relapse may pose a risk for severe GVHD, specifically in the mismatched or haploidentical transplantation setting. Manipulation of CIK cells may reduce risk for GVHD without affecting the anti-tumor potential.MethodsIn this pre-clinical study, we provide a detailed functional comparison of conventional and irradiated, CD56-enriched or T-cell receptor α/β-depleted CIK cells.ResultsIn vitro analysis showed retained anti-leukemic and anti-tumor potential after CIK cell manipulation. Even being sequentially infused into immunodeficient mice grafted with malignant cells, cytotoxic effects were fewest after irradiation but were improved by CD56 enrichment and were best with conventional CIK cells. Hence, considering the proliferative capacity of inoculated malignancies and effector cells, a single dose of conventional CIK cells resulted in prolonged disease-free survival and elimination of rhabdomyosarcoma cells, whereas sequential infusions were needed to achieve comparable results in leukemia-bearing mice. However, this mouse model has limitations: highly effective conventional CIK cells demonstrated both limited xenogenic GVHD and low alloreactive potential in vitro.ConclusionsOur study revealed that conventional CIK cells demonstrate no significant alloreactive potential but provide the strongest anti-tumor efficacy compared with manipulated CIK cells. Conventional CIK cells may therefore be tested in high numbers and short-term intervals in patients with impending relapse even after mismatched transplantation.     

Adoptive immunotherapy of a newly induced sarcoma: immunologic characteristics of effector cells

A newly induced syngeneic transplantable sarcoma, MCA 105, was used for studies of the biologic characteristics of fresh noncultured and secondarily in vitro sensitized (IVS) cells with antitumor reactivity. Fresh spleen cells harvested from mice immunized to the MCA 105 tumor by a mixture of viable tumor cells and Corynebacterium parvum exhibited no detectable cytotoxic activity to MCA 105 tumor targets in a 4-hr chromium-release assay, and adoptive transfer of these cells mediated the specific regression of established MCA 105 tumors. Phenotypic analysis of fresh, noncultured immune cells revealed that the therapeutically effective cells expressed both the Lyt-1 and the Lyt-2 T cell differentiation antigens. The therapeutic efficacy of fresh noncultured immune cells was not augmented by the concomitant administration of exogeneous interleukin 2 (IL 2). Secondary IVS of fresh immune cells with irradiated MCA 105 tumor stimulator cells resulted in the generation of tumor-specific cytotoxic effector cells. The generation of cytotoxic effector cells required Lyt-1+, 2+ cytotoxic precursor cells. Effective adoptive immunotherapy with these IVS immune cells, unlike fresh noncultured immune cells, depended on the concomitant administration of IL 2. Furthermore, the generation of therapeutically effective cells did not require the specific stimulation by MCA 105 tumor cells, because cultures of MCA 105 immune spleen cells with FBL-3 lymphoma cells in vitro also contained in vivo functional immune effector cells. These cells, however, possessed no detectable MCA 105 cytotoxic activity in vitro. Although this observation suggests that a noncytotoxic cell population is sufficient to initiate tumor regression in vivo, it does not exclude the possibility that cytolytic cells are generated in vivo after adoptive transfer of these cells. As a whole, our results indicate that secondary IVS functional immune effector cells are characteristically distinct from freshly harvested immune cells.     

Adoptive cellular immunotherapy: NK cells and bone marrow transplantation

Allogeneic bone marrow transplantation (BMT) has been increasingly used for the treatment of both neoplastic and non-neoplastic disorders. However, serious obstacles currently limit the efficacy and thus more extensive use of BMT. These obstacles include: graft-versus-host disease (GVHD), relapse from the original tumor, and susceptibility of patients to opportunistic infections due to the immunosuppressive effects of the conditioning regimen.Overcoming these obstacles is complicated by dual outcome of existing regimens; attempts to reduce GVHD by depleting T cells from the graft, result in increased rates of tumor relapse and failure of engraftment. On the other hand, efforts to increase graft-versus-tumor (GVT) effects of the transplant also promote GVHD. In this review, the use of natural killer (NK) cells to overcome some of these obstacles of allogeneic BMT is evaluated. Adoptive immunotherapy using NK cells after allogeneic BMT has several potential advantages. First, NK cells can promote hematopoiesis and therefore engraftment by production of hematopoietic growth factors. Second, NK cells have been shown to prevent the incidence and severity of GVHD. This has been shown to be at least partially due to TGF-beta, an immunosuppressive cytokine. Third, NK cells have been shown to augment numerous anti-tumor effects in animals after BMT suggesting a vital role of NK cells in mediating GVT effects. Finally, NK cells have been demonstrated to affect B cell recovery and function in mice. Therefore, understanding the mechanisms of beneficial effects of NK cells after BMT may lead to significant increases in the efficacy of this procedure.     

Dendritic cells combining with cytokine-induced killer cells synergize chemotherapy in patients with late-stage non-small cell lung cancer

Background  

Lung cancer is the leading cause for cancer-related mortality and morbidity, and the survival of late-stage non-small cell lung cancer (NSCLC) remains poor. We hereby evaluate conventional chemotherapy followed by immunotherapy using dendritic cells and cytokine-induced killer cells in the treatment for late stage of NSCLC.     

Experimental study on the treatment of intracerebral glioma xenograft with human cytokine-induced killer cells

Objective. To investigate the phenotype changes and proliferation activities of cytokine-induced killer cells (CIKs) and lymphokine-activated killer cells (LAKs) from healthy donor, and the cytotoxicities of CIKs and LAKs to human in vitro glioma cell lines U251 and U87. Therapy of CIK intratumoral injection was evaluated in nude mouse models. Methods. CIK cells were induced from peripheral blood mononuclear cells (PBMC) of healthy donors with multiple cytokines. Phenotype analysis of CIKs and LAKs was performed with flow cytometer (FCM). The specific cytotoxicities of CIKs and LAKs against cell line U251 and U87 were determined by LDH method. After intracerebral injection of CIKs, the distribution of CIKs and the inflammatory reaction of their surrounding brain tissue were observed through continuous pathological sections. In vivo anti-tumor activity of CIKs was evaluated in athymic nude mice with intracerebral xenotransplanted U251 glioma by MRI. Results. Amount of CIKs was increased (49.83+/-2.04) times and double positive cells, CD3(+)/CD56(+) cells, were increased from (3.36+/-1.85%) to (44.07+/-14.14%) with elevated absolute amount over 1000 times after 2 week culture. In vitro experiments demonstrated that compared with LAK, CIKs possessed more obvious cytotoxic activity to U251 and U87. In vivo experiments showed that there was no severe inflammatory reaction in brain tissue. CIKs can markedly inhibit intracranial xenotransplanted glioma growth by intracranial injection (P<0.01). Conclusion. CIKs are a kind of highly effective immune cells which have a strong suppressive effect on growth for in vitro and in vivo glioma. Local injection of CIKs does not produce severe damage to normal brain tissue and is likely to be used in clinical adoptive immunotherapy of intracerebral glioma.     

The cytotoxic potential of interleukin-15-stimulated cytokine-induced killer cells against leukemia cells

Background aimsCytokine-induced killer (CIK) cells may serve as an alternative approach to adoptive donor lymphocyte infusions (DLI) for patients with acute leukemia relapsing after haplo-identical hematopoietic stem cell transplantation (HSCT). We investigated the feasibility of enhancing CIK cell-mediated cytotoxicity by interleukin (IL)-15 against acute myeloid and lymphoblastic leukemia/lymphoma cells.MethodsCIK cells were activated using IL-2 (CIK_IL-2) or IL-15 (CIK_IL-15) and phenotypically analyzed by fluorescence-activated cell sorting (FACS). Cytotoxic potential was measured by europium release assay.ResultsCIK_IL-2 cells showed potent cytotoxicity against the T-lymphoma cell line H9, T-cell acute lymphoblastic leukemia (T-ALL) cell line MOLT-4 and subtype M4 acute myeloid leukemia (AML) cell line THP-1, but low cytotoxicity against the precursor B (pB)-cell ALL cell line Tanoue. IL-15 stimulation resulted in a significant enhancement of CIK cell-mediated cytotoxicity against acute lymphoblastic leukemia/lymphoma cell lines as well as against primary acute myeloid and defined lymphoblastic leukemia cells. However, the alloreactive potential of CIK_IL-15 cells remained low. Further analysis of CIK_IL-15 cells demonstrated that the NKG2D receptor is apparently involved in the recognition of target cells whereas killer-cell immunoglobulin-like receptor (KIR)-HLA mismatches contributed to a lesser extent to the CIK_IL-15 cell-mediated cytotoxicity. In this context, CD3 ⁺ CD8 ⁺ CD25 ⁺ CD56^? CIK_IL-15 cell subpopulations were more effective in the lysis of AML cells, in contrast with CD56 ⁺ CIK_IL-15 cells, which showed the highest cytotoxic potential against ALL cells.ConclusionsThis study provides the first evidence that CIK_IL-15 cells may offer a therapeutic option for patients with refractory or relapsed leukemia following haplo-identical HSCT.