OBJECTIVETo investigate the effect of up-regulation of Rap1GAP on the invasion ability of leukemic HL-60 cells in vitro, and to establish leukemia mouse model to verify the effects in vivo.

METHODSQuantitative RT-PCR and Western blot methods were used to detect the expression of Rap1GAP in Venus/HL-60 (vehicle control) and Rap1GAP/HL-60 cells (R1 andR2). Transwell method was used to examine the invasion ability in vitro. Quantitative RT-PCR and gelatin zymograph were used to study the expression of MMP-2 and MMP-9. Four-week-old BALB/c nu/nu mice were pre-treated and inoculated with leukemic cells from different groups, several index including survival time were then monitored.

RESULTSRap1GAP mRNA level of R1 and R2 increased about 16-17 folds as compared to the control cells. The invasion rate of R1 and R2 are (55 ± 5)% and (59 ± 4)%, which are significantly higher than (14 ± 4)% of the control cells. The mRNA level of MMP-9 was up-regulated about 12.0 folds in R1 and R2 cells compared to the corresponding control cells. The median survival times of R1 and R2 mice are (32.00 ± 1.85) d and (33.37 ± 2.50) d, respectively, which are shorter than (43.62 ± 2.32) d of the control group. Three mice of R1 and R2 groups showed leukemic cells infiltration in meninges tissue, and the genes of Rap1GAP and MMP-9 were amplified by PCR method.

CONCLUSIONUp-regulated expression of Rap1GAP increased the invasion ability of HL-60 cells accompanied with enhancement of MMP-9 expression in vitro, and the experiment in mouse model also confirmed that Rap1GAP enhanced the invasion of HL-60 cells in vivo.