The Synergistic Effects Of Bortezomib And Adriamycin-induced Apoptosis In Multiple Myeloma Cells

Objective: 1. To study the inhibitory effect of bortezomib and adriamycin on the apoptosis of multiple myeloma cells (RPMI8226); 2. To study the effects of bortezomib on the cell adhesion and the cell adhesion mediated adriamycin resistance of RPMI8226 cells.Methods: The effects of bortezomib and/or adriamycin on the apoptosis of RPMI8226 cells were detected by flow cytometry analysis. Synergetic effect of bortezomib and adriamycin was analyzed by median-effect principle. The adhesion rates of RPMI8226 cells to fibronectin or bone marrow stroma-cells (BMSCs) were detected by 5(6)-Carboxyfluorescein diacetate N-succinimidyl ester (CFSE)labeling and flow cytometry analysis. The adriamycin resistance mediated by cell adhesion was determined by MTT assay in the following four groups:①FN/BMSCs+Adr group;②BSA+Adr group;③Bor+FN/ BMSCs+Adr group;④Bor +BSA+Adr group.Results: The apoptosis of RPMI8226 cells was induced by bortezomib and the IC50 value was (51.23±4.36)nmol/l. The IC50 value of adriamycin on RPMI8226 cells was (1.15±0.13)μmol/L. While when adriamycin was combined with bortezomib(10nmol/L), Its IC50 value was (0.81±0.17)μmol/L, which was significantly lower than single adriamycin (P<0.05). These results showed that the combination of bortezomib and adriamycin had synergistic effect. When RPMI8226 cells had been adhered to FN or BSA-coated wells for 2 and 12 hours, the adhesion rates were (55.78±1.56) % and (60.34±2.46) % respectively(P > 0.05). While if RPMI8226 cells were pretreated with Bortezomib (10nmol/L), the adhesion rates were decreased to (34.24±1.29)% and (35.58±1.32)% respectively which were significantly lower than those of untreated groups (P<0.05). When RPMI8226 cells had been adhered to BMSCs or BSA-coated wells for 2 and 12 hours, the adhesion rates were (50.47±2.56) % and (61.27±3.86) % respectively (P>0.05). While if RPMI8226 cells were pretreated with bortezomib (10nmol/L), the adhesion rates were decreased to (40.54±1.29)% and(46.57±1.79)respectively which were significantly lower than those of untreated groups (P<0.05). When RPMI8226 cells had been adhered to FN-coated plates for 12h, the IC50 value of adriamycin was (1.80±0.24)μmol/L which was significantly higher than BSA group (1.18±0.13)μmol/L (P<0.05). While if RPMI8226 cells were pretreated with bortezomib (10nmol/L), the IC50 values of adriamycin in FN and BSA groups were (0.93±0.09)μmol/L and (0.82±0.07)μmol/L respectively, which had no significant difference (P>0.05). When RPMI8226 cells had been adhered to BMSCs-coated plates for 12h, the IC50 value of Adr was (1.87±0.24)μmol/L which was significantly higher than BSA group (P<0.05). While if RPMI8226 cells were pretreated with bortezomib (10nmol/L), the IC50 values of adriamycin in BMSCs and BSA groups were (1.08±0.09)μmol/L and (0.80±0.08)μmol/L respectively, which had no significant difference (P>0.05).Conclusions: 1. Bortezomib and adriamycin showed synergistic inhibitory effects on the apoptosis of RPMI8226 cells; 2. Bortezomib can decrease the adhesion rates of RPMI8226 cells to fibronectin and BMSCs; 3. Bortezomib can reverse RPMI8226 cells'adriamycin resistance mediated by cell adhesion to FN or BMSCs.