OBJECTIVETo explore the synergetic effect of norcantharidin (NCTD) and adriamycin (ADR) on the proliferation and apoptosis of multiple myeloma (MM) cells.

METHODSHuman MM cell line U266 cells were treated with NCTD alone (10 µmol/L) or in combination with ADR (0.25 µmol/L). MTT and Annexin V/PI staining were used to determine cell viability and apoptosis. The protein expression of nuclear factor-κB P65 (NF-κB P65), phosphorylated NF-κB p65 (p-NF-κB p65), NF-κB P65 inhibitor IκBα, phosphorylated IκBα (p-IκBα), survivin, Bcl-2 and Bax were determined by Western blot. Immunohistochemistry was used to determine the expression of vascular endothelial growth factor (VEGF).

RESULTS(1) NCTD potentiated the cytotoxicity and pro-apoptotic effects induced by ADR. The combination of NCTD and ADR had synergistic anti-proliferation effect. (2) Combination of ADR and NCTD downregulated the expression of nuclear NF-κB P65 and cytoplasm p-IκBα induced by ADR. The expression of nuclear NF-κB P65 and cytoplasm p-IκBα decreased from 2.08 ± 0.29 and 0.39 ± 0.07 to 0.48 ± 0.08 and 0.02 ± 0.01 respectively, while the expression of the cytoplasm NF-κB P65 and IκBα were unchanged in the ADR alone group and the combined group. (3) The expression of survivin and bcl-2 decreased from 0.31 ± 0.05 and 0.23 ± 0.05 to 0.03 ± 0.02 and 0.05 ± 0.02, while the expression of Bax increased from 0.46 ± 0.06 to 0.62 ± 0.08 respectively in ADR alone group and combined group. (4) The positive rate of VEGF in ADR group and combination group were (44.6 ± 4.4)% and (27.0 ± 2.1)% respectively, indicating that NCTD could potentiate the inhibition effect on VEGF induced by ADR.

CONCLUSIONSThe results suggest that NCTD can potentialize the chemosensitivity of multiple myeloma cells to ADR through regulating NF-κB/IκBα signaling pathway and NF-κB-regulated gene products including survivin, Bcl-2, Bax and VEGF.