Study of the effects of berberine combined with bortezomib on multiple myeloma cell line U266 cells

Objective: To investigate the effects of berberine in combination with bortezomib on proliferation and apoptosis of multiple myeloma (MM) cell line. Methods: MM cell line U266 cells were treated with berberine and/or bortezomib. The effects of berberine and/or bortezomib on proliferation of cells were measured by methylthiazolyl tetrazolium bromide (MTT). Flow cytometric Annexin Ⅴ/PI double staining method was used to detect effect of either drug alone or in combination on apoptosis of MM cell line U266. ELISA was used to measure the expression of casepase-3,-8,-9 affected by the two drugs. Western blot was used to detect the expression of the apoptosis-related protein TRADD and FADD. King formula was used to determine if there was a synergistic effect of berberine in combination with bortezomib. Results: ① Both berberine and bortezomib as single agent had dose- and time-dependent effects of proliferation inhibition on U266 cells. Berberine (20 μmol/L) and bortezomib (5 nmol/L) had a synergistic effect of proliferation inhibition (Q value: 1.31-1.65). ② The proportion of early stage apoptosis in both single agent groups and combination group significantly increased compared to control group (P< 0.05). Berberine and bortezomib had a synergistic effect on cell apoptosis (Q value after 6 h and 12 h were 0.896 and 1.197, respectively). ③ Berberine in combination with bortezomib significantly upregulated expressions of caspase-3, -8 and -9, which were statistically significant (P<0.05). ④Berberine in combination with bortezomib significantly upregulated expressions of TRADD (0.91±0.01, 0.70±0.01) and FADD (0.98±0.01, 0.98±0.01) compared with control group (both P<0.05). Conclusion: Berberine in combination with bortezomib had synergistic effects on proliferation inhibition and apoptosis, which were mediated by up-regulated levels of TRADD and FADD.