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Adoptive cellular immunotherapy is an important treatment to eliminate residual tumor cells after hematopoietic stem-cell transplantation. Bone marrow mesenchymal stem cells (MSC) have previously been shown to exert immunoregulation functions, including inhibition of proliferation and killing activities of T cells and natural killer (NK) cells in vitro and reduction of the graft-versus-host disease. MSC can survive in vivo for a long period of time, the influence of MSC on the antitumor activity of subsequently infused immune killer cells is not clear. The aim of this study was to investigate the influences of MSC infused via different paths and at different times on the antitumor activities of cytokine-induced killer (CIK)/NK cells derived from umbilical cord blood in K562 NOD/SCID mice. The potential interaction mechanisms of MSC and CIK/NK cells infused through different paths using different intervals in vivo were subsequently explored. The results show that the antitumor activities of CIK/NK cells was inhibited by MSC when injected via the same path (tail vein), and the suppressive effect of MSC on CIK/NK cells were less pronounced when they were injected separately through different paths. There were no effects of MSC on the antitumor activities of CIK/NK cells if the MSC and CIK/NK cells were injected with a 48-h interval. Moreover, the suppressive effect continuous, even if MSC were infused 48 h earlier than CIK/NK cells. It suggests that pre-injected MSC can reduce the antitumor activities of CIK/NK cells in vivo. The probable mechanisms are that MSC and CIK/NK cells might have a greater opportunity to meet and interact if they are injected simultaneously via the same path. The suppression of MSC on CIK/NK cells in vivo mainly takes place in the reticuloendothelial system, including the lung and the liver.

The efficacy of various combinations of stem cell factor (SCF), FLT3 ligand, interleukin (IL)-2, IL-7 and IL-15 to induce and expand cord blood-derived cytokine-induced killer (CIK) cells was investigated. There were three treatment groups: group A: SCF combined with IL-2, IL-7 and IL-15; group B: SCF, FLT3 ligand combined with IL-2, IL-7 and IL-15, and group C: IL-2, IL-7 and IL-15, the control group. Proliferation rates of CD3(+)CD56(+) CIK cells and CD3(-)CD56(+) natural killer (NK) cells were highest in group B; expansion of CIK cells increased 796.1 ± 278.5-fold, and that of NK cells increased 36.6 ± 3.5-fold. All expanded cord blood-derived CIK/NK cells showed cytotoxic activity against the K562 cell line. Interestingly, the cytotoxicity of group A was highest and significantly higher than that of other groups. These protocols might provide an alternative choice for CIK/NK cell expansion.

The study was aimed to explore the distribution and interaction mechanism of human bone marrow mesenchymal stem cells (MSC) and cord blood cytokine-induced killer (CIK)/natural killer (NK) cells infused via different ways at different times in NOD/SCID mice. 5 microl 1, 1'-dioctadecyl-3, 3, 3', 3'-tetramethylindocarbocyanine perchlorate (DiI) dye(red) was added in suspension of MSC per ml, and 1 microl carboxyfluorescein diacetate, succinimidyl ester(CFDA SE) dye(green) was added in suspension of CIK/NK cells per ml. The amounts of MSC and CIK/NK cells infused in each 6 NOD/SCID mouse were 1 x 10(6) (0.1 ml) and 1 x 10(7) (0.1 ml) respectively. All mice were divided into 4 groups, each group consisted of 6 mice. Group A: MSC (intravenous infusion, iv) + CIK/NK cells (iv) at the same time, group B: MSC (iv) + CIK/NK cells (iv) at 48 hours after infusion of MSC; group C: MSC (intramedullary infusion, im) + CIK/NK cells (iv) at the same time; group D: MSC (im) + CIK/NK cells (iv) at 48 hours after infusion of MSC. 3 NOD/SCID mice were sacrificed per batch at 24 hours and 48 hours after infused CIK/NK cells. Frozen sections of liver, spleen, lung and kidney were prepared, and then followed by counting the amounts of red and green fluorescence cells under fluorescence microscope, and calculating the ratio of MSC to CIK/NK cells for reflecting the interaction of MSC and CIK/NK cells in mice, and for showing the suppressive intensity of MSCs on CIK/NK cells. The results showed that the sums of average ratios of MSC to CIK/NK cells in lung, liver and spleen of group A and B were higher than that in group C and D at 24 hours and 48 hours respectively after infusing CIK/NK cells. The sum of average ratios of MSC to CIK/NK cells in group A was slightly higher than that in group B at 24 hours and 48 hours after infusing CIK/NK cells, but there was no significant difference between them. The sum of average ratios of MSC to CIK/NK cells in lung, liver and spleen in group C was slightly lower than that in group D at 24 hours after infusing CIK/NK cells, but reversed at 48 hours later and there was no significant difference between them. The sums of average ratios of MSC to CIK/NK cells in lung, liver and spleen in group A, B, C and D were all higher than those in kidney at 24 and 48 hours respectively after infusing CIK/NK cells. It is concluded, the MSC and CIK/NK cells may interact if they are infused via the same way and at the same time, the location where the suppression of MSC on CIK/NK cells occur in vivo may be reticulo-endothelial systems in lungs and livers.

Objectives: To study the in vivo efficacy and the safety of cord blood derived CIK/NK cells stimulated by K562-dendritic cells (DC) fusion vaccines in NOD/SCID mice model for human erythroleukemia., Methods: DC and CIK /NK cells were both derived from cord blood mononuclear cells. DC were fused with inactivated K562 leukemia cell by PEG to produce K562-DC fusion vaccines. K562-DC fusion vaccines were co-cultured with CIK/NK cells to prepare K562-DC fusion vaccine stimulated CIK/NK cells. NOD/SCID mice were inoculated with 1 x 10(6) K562 cells. 24 hours later, 1 x 10(7) vaccines stimulated CIK/ NK cells and 1 x 10(7) CIK/NK cells were transfused into the NOD/SCID mice. NOD/SCID mice without inoculation of K562 cells were used as control group. CD13 and CD56 positive cells were assayed by flow cytometry., Results: All the leukemia NOD/SCID mice without therapy died within 39 days, tumor was found in 5 of 8 mice. One of 8 leukemia mice treated with K562-DC fusion vaccines stimulated CIK/NK cells died at the 65th day, the anti-tumor response rate was 87.5%. Two of the leukemia mice treated with CIK/NK cells died at the 56th and 65th day respectively, the anti-tumor response rate was 75%. There was no significant difference in survival time between these two groups, and both survivals were longer than that of the control group. There was no significant difference in CD13 positive cells in the survival mice between these two groups, and both of that were less than that of the control mice. There was no significant difference in CD56 positive cells between the two treated groups and the control group., Conclusions: Cord blood derived CIK/ NK cells stimulated by inactivated tumor cells retain the cytotoxicity and do not develop tumor in vivo.

Objectives: To evaluate the effects of K562-dendritic cell (DC) and Raji-DC fusion vaccines on the cytotoxicity of cord blood (CB) derived cytokine-induced killer/natural killer (CIK/NK) cells., Methods: DC and CIK/NK cells were derived from CB mononuclear cells. CB-DC were fused with inactivated K562 or Raji cells by PEG to form K562 or Raji-DC fusion vaccine. The CIK/NK cells stimulated by different co-culture antigens were three groups: K562-DC or Raji-DC fusion vaccine group, inactivated K562 or Raji plus DC group, and CB-DC alone group. The cytotoxicity of CIK/NK cells stimulated by different co-culture antigens was measured by MTT test., Results: All the antigens used for stimulation could enhance the cytotoxicity of CB-CIK/NK cells, with no specificity difference. At 20:1 effector-target ratio, the cytolytic activities of K562-DC and Raji-DC fusion vaccine groups against Raji cells were (75.44 +/- 4.19)% and (81.33 +/- 4.18)% respectively (P < 0.05); and that of inactivated K562 + DC and Raji + DC group against Raji cells were (73.12 +/- 4.22)% and (80.49 +/- 4.27)%, respectively (P < 0.01). There was no significant difference in the cytotoxicity to K562 cells between the two fusion vaccine groups (P > 0.05). The cytotoxicity of CB-CIK/NK cells immunized by Raji cells was higher than that by K562 cells. In CIK/NK cells co-stimulated by the same tumor antigen, there was no significant difference in the cytotoxicity between DC fusion vaccine group and inactivated cells plus DC group to different tumor cells., Conclusions: The cytotoxicity of CB-CIK/NK cells to tumor cells was not specific. There was no significant difference in the cytotoxic activity of CB-CIK/NK cells between the DC fusion vaccine group and inactivated cells plus DC group.

To explore the efficacy of the different combinations of stem cell factor (SCF), FLT3 ligand (FL) and interleukin (IL) 2, 7, 15 on the induction and expansion of cord blood (CB) derived CIK/ NK cells in vitro, according to the different combinations of cytokines, combinations of cytokines were divided into 3 groups: group A (SCF + IL2 + IL7 + IL15), group B (SCF + FL + IL2 + IL7 + IL15) and group C (IL2 + IL7 + IL15 as control group). At 21 days of culture, the proportion and the expansion rate of CD3(+)CD56(+) CIK cells and CD3(-)CD56(+) NK cells were measured. The results showed that at 21 days in culture, the percentages of CD3(+)CD56(+) CIK cells derived from CB-MNC in group A, B and C were (19.84 +/- 2.93)%, (26.20 +/- 4.05)%, (24.03 +/- 4.99%) and that of NK cells were (49.60 +/- 1.40)%, (51.16 +/- 6.45)% and (30.85 +/- 8.12)%, respectively. The proliferation of CD3(+)CD56(+) CIK cells and CD3(-)CD56(+) NK cells was the most effective in group B (SCF + FL + IL2 + IL7 + IL15). Expansion multiple of CIK cell number increased from 575.81 +/- 221.72 (control) to 796.09 +/- 278.47 with peak value of 1 313, and that of NK cells increased from 30.39 +/- 14.47 (control) to 65.85 +/- 30.83 with peak value of 121.06. In conclusion, a proper cytokines (SCF + FL + IL2 + IL7 + IL15) culture system can effectively induce and expand CB CD3(+)CD56(+) CIK cells and CD3(-)CD56(+) NK cells simultaneously.

Objective: To explore the most efficient culture system which can induce cord blood (CB)-mononuclear cells (MNC) to differentiate into mature T/NK cells in vitro., Methods: The CB MNCs were cultured in six culture systems respectively for 4 weeks. The T/NK cell surface phenotypes were analyzed by flow cytometry and the absolute numbers of nucleated cells (NCs) were counted at each time point. Moreover, cell morphology was identified by Giemsa-Wright staining, and cytotoxicity of the cultured cells to K562 and Raji tumor cells was also evaluated by MTT method., Results: Cultured in the cytokine cocktail of SCF + FLT-3L + IL-7 + IL-15 + TNF-alpha + IL-2, the NCs were (20 approximately 26) x 10(6)/ml in numbers at day 22. The percentage of lymphocytes in the NCs and that of CD(3)(+) T cells in the lymphocytes both exceeded 90% at the same time. Most of the CD(3)(+) T cells were CD(3)(+)CD(8)(+) and the percentage of CD(3)(+)CD(4)(+) T cells declined gradually. The percentage of CD(3)(+)CD(56)(+) NKT cells and gamma delta(+)T cells in the lymphocytes arised from lower than 2% to 30% approximately 40% and 10% approximately 15%, respectively. CD(3)(-)CD(56)(+) NK cells were not expanded. The cytotoxic activity of the cultured cells to K562 and Raji cells at an effector:target (E:T) ratio of 50:1 was over 75% and about 32% approximately 65%, respectively., Conclusion: The most efficient culture system which can induce CB MNC to differentiate into mature T/NK cells in vitro is the cytokines cocktail of SCF + FLT-3L + IL-7 + IL-15 + TNF-alpha + IL-2, and the optimum culture time is 22 days.