Influences of bone marrow mesenchymal stem cells infusion on anti-tumor activities of cytokine-induced killer/natural killer cells from umbilical cord blood in K562 NOD/SCID mice

Objective To explore the influences of bone marrow mesenchymal stern cells (BMMSC) infused via different ways and at different time points on anti-tumor activities of cytokineinduced killer (CIK)/natural killer (NK) cells from umbilical cord blood in K562 NOD/SCID mice.Methods Fifty-six NOD/SCID mice were divided into 7 groups. The following experiments were carried out at 12th h after K562 cells were infused. Group A: BMMSC (intravenous injection,i. v. ) +CIK/NK cells (i. v. ,at the same time); Group B: BMMSC (i. v. ) + CIK/NK cells (i. v. ,48 h after BMMSC infusion) ; Group C: BMMSC (cavitas medullaris) + CIK/NK cells (i. v. ,at the same time) ;Group D: BMMSC (cavitas medullaris) + CIK/NK cells (i. v. ,48 h after BMMSC infusion) ; Group E: CIK/NK cells (i. v. ); Group F: CIK/NK cells (i. v. ,50 h after K562 cells inoculation); Group G (control group) : No other cells were infused in addition to K562 cells. The survival curve of NOD/SCID mice in each group was drawn, and the tumor cell load of the peripheral blood, bone marrow,liver,spleen and lung was detected by using morphology, flow cytometry and histological methods.Results The average survival time of groups A,B,G was significantly shorter than that of groups C,D, E, F (P＜0.05). There was no significant difference in average survival time among groups A, B and G and that between groups C, D, E and F (P＞0. 05). The ratio of tumor cells on peripheral blood and bone marrow smears in groups A, B and G was higher than that in groups C, D, E and F. The expression of human CD33 as the tumor marker in peripheral blood, bone marrow and liver, spleen,lung tissue homogenates of groups A,B and G was higher than that of group C,D, E and F (P＜0. 05). Whereas, the expression of CD33 in the liver, spleen, lung tissue homogenate of groups A and G was significantly higher than that of group B. The expression of CD33 in the lung tissue homogenate of group C was significantly higher than that of group D (P＜0. 05). Conclusion The anti-tumor activity of CIK/NK cells could be inhibited by BMMSC distinctly when they were injected via the same way (tail vein), and inhibitory effect of BMMSC on CIK/NK cells may be lightened when they were injected separately. It prompts BMMSC in vivo may inhibit the anti-tumor effects of CIK/NK cells,even if BMMSC are infused 48 h earlier than CIK/NK cells. Key words: NOD/SCID mice;  Bone marrow;  Mesenchymal stem cell transplantation;  Umbilical cord blood; Killer cells,lymphokine-activated; Anti-tumor effect