MMP9 and leukemia: To assess whether the mRNA expression levels of uPA, uPAR, PAI-1, MMP-9, and VEGF-A were up-regulated in other leukemia cells co-cultured with BMSCs, we co-cultured BMSCs with HL60 and checked the expression of uPA, uPAR, PAI-1, MMP-9, and VEGF in the cells by quantitative real time polymerase chain reaction (Q-PCR).