Objective   To explore the possible roles of apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) expression in the bone marrow stromal cells (BMSCs) form multiple myeloma (MM) patients.    Methods   The expression of APE1/Ref-1 protein in BMSCs isolated from the bone marrow samples of 35 initial cases

11 relapse/refractory cases with MM and 10 cases health individuals were detected by immunocytochemistry. Before and after the transfection of the adenoviral vector Adv5-APE1/Ref-1 siRNA

the concentrations of interleukin-6 (IL-6) and interleukin-8 (IL-8) in the supernatant of BMSCs were measured with ELISA

and the cell cycles proliferation of BMSCs were detected with flow cytometry.    Results   The expression of APE1/Ref-1 protein in the cultured BMSCs was significantly higher than in normal BMSCs (P0.05). APE1/Ref-1 siRNA obviously inhibited the expression of the protein in MM or normal BMSCs. Transfected with Adv5-APE1/Ref-1 siRNA

the MM or normal BMSCs gradually decreased the levels of IL-6 and IL-8 secretion in a time course. In 72 h after the transfection

the amounts of IL-6 and IL-8 in the BMSCs supernatant reached the lowest levels as following

IL-6 (246.29±46.51) pg/ml and IL-8 (118.77±18.08) pg/ml in initial MM group

and IL-6 (365.09±75.25) pg/ml and IL-8 (188.71±33.76) pg/ml in relapse/refractory group (P0.01).    Conclusion   The abnormal expression of APE1/Ref-1 protein in MM BMSCs may lead to many changes of biological function. APE1/Ref-1 siRNA knocks down the expression of APE1/Ref-1 protein in BMSCs

and inhibits the production of IL-6 and IL-8 in MM BMSCs

thus indirectly reduces the proliferation or benefit apoptosis of myeloma cells.