Relationship Between The Expression Of B7-H2 On Leukemic Cells And Graft-versus-leukemia Reaction After Allogeneic Hematopoietic Stem Cell Transplantation

Objective The aim of this study was to examine the effect of B7H2 gene silencing in mice A20 cell on the graft-versus-leukemia (GVL) reaction after allogeneic bone marrow transplantation. Methods Forty-seven new patients with adult de novo acute leukemia, who were diagnosed according to the French-American-British criteria, were the subjects of this study. We choose A20 as target cell. The test principle is based on target cell labeling with CFSE and subsequent DNA-labelling with PI for identification of target cells with compromised cell membranes. Effectors and targets were incubated at E/T ratios from 50:1 to 10 : 1 for 12 h, collect 1000 targetevents and analyze specific cytotoxicity. We introduced shRNA-pGCsi which could inhibite the expression of B7H2 in A20 cells and plasmid vector pGCsi into A20 cell line using lipofectamine method respectively. Then we infused them into mice intravenously to erect the model of GVL respectively to examine the effect of B7H2 gene silencing in mice A20 cell on the graft-versus-leukemia (GVL) reaction after allogeneic bone marrow transplantation. Result The cells from a substantial number of acute leukemia cases expressed B7-H2 molecules [percentages of B7-H2 positive cases in AML and ALL were 25%(n= 29) and 31%(n= 19). Mean percentages of B7-H2-positive cells in patients of high risk was significantly higher than those of low risk[Mean percentages were 4%(n= 5) and 15%(n=7), respectively].We observed that B7H2 blocked A20 cells obtained more cytolytic activity than B7H2 positive A20 cells at E/T ratios 30:1,20:1 and 10:1 [P=0.0062, 0.0287,0.0462, respectively]. B7H2 blocked A20 cells obtained no more cytolytic activity than B7H2 positive A20 cells at E/T ratios 40:1 and 50:1 [P=0.1318,0.2804, respectively].The difference between GVL group one and GVL group two was statistically significant(P=0.005), but no difference was observed among Leakemia group (P=0.640). Conclusion Our results indicate the expression of functional B7-H2 molecules, and this molecules may facilitate progression of acute leukemia. These results indicate that B7H2 blocked A20 cells obtained more cytolytic activity than B7H2 positive A20 cells at proper E/T ratios. Mice that received B7H2 gene silenced A20 cells demonstrated delayed mortality and delayed tumor progression.