Norcantharidin enhances bortezomib-antimyeloma activity in multiple myeloma cells in vitro and in nude mouse xenografts.

Norcantharidin (NCTD), the demethylated analog of the Chinese medicine cantharidin, exhibits anti-myeloma activity by inactivating nuclear factor-κB (NF-κB), which is implicated in multiple myeloma (MM) cell survival and resistance to bortezomib (BTZ). We investigated whether NCTD could potentiate the anti-tumor activity of BTZ in MM. NCTD inhibited the proliferation of MM cells and potentiated the anti-myeloma effects of BTZ by down-regulating IKKα and p-IκBα, which induced the accumulation of IκBα and inhibited the constitutive activation of NF-κB. This effect was correlated with the suppression of NF-κB-regulated gene products. Furthermore, a chemotherapy-potentiating effect of NCTD on BTZ was also observed in vivo. Our study demonstrated that NCTD and BTZ exhibit significant therapeutic effects on MM through the NF-κB signal pathway in vitro and in vivo. Future studies will investigate the combined effects of NCTD and BTZ in patients with MM.

[Norcantharidin potentialize the chemosensitivity of adriamycin through the NF-κB/IκBα signaling pathway].

OBJECTIVE: To explore the synergetic effect of norcantharidin (NCTD) and adriamycin (ADR) on the proliferation and apoptosis of multiple myeloma (MM) cells. METHODS: Human 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. CONCLUSIONS: The 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.