Abstract: Objective To determine the mRNA and protein levels of urokinase plasminogen activator receptors (uPAR) in bone marrow fluid and bone marrow tissue from multiple myeloma (MM) patients and assess association of uPAR level with prognosis of MM. Methods uPAR levels in bone marrow fluid of 22 MM patients at the stable and progressive stages and 18 iron deficiency anemia patients with normal bone marrow (control) were examined by ELISA. Furthermore, uPAR expression in bone marrow tissue was investigated by RT-PCR and Western blot, respectively. The distribution of uPAR in MM cells was examined using immunofluorescence staining. The pathological changes in different stages of MM patients were studied by HE staining. Results uPAR level in bone marrow fluid of MM patients (1.52±0.32 μg/ml) was found to be higher than that in the control group (0.98±0.15 μg/ml). Interestingly, uPAR protein (0.686±0.075 vs. 0.372±0.043, P<0.05) and mRNA (2.51±0.46 vs. 4.46±1.15, P<0.05) expression levels of MM patients at the progressive stage were significantly higher than those at the stable stage. The expression of uPAR in MM bone marrow was confirmed by immunofluorescence staining. Moreover, HE staining revealed a great increased number of nucleated cells and severe impairment of hematopoietic function in the bone marrow of patients with progressive-stage myeloma. Conclusion Our study reveals that uPAR expression is positively correlated with the development and progress of MM.

Key words: multiple myeloma, urokinase-type plasminogen activator receptor, bone marrow, urokinase