A novel NF-κB inhibitor DHMEQ selectively targets constitutive NF-κB activity and induces apoptosis of multiple myeloma cells in vitro and in vivo

Multiple myeloma (MM) is a fatal lymphoid malignancy that is incurable with conventional modalities of chemotherapy. Strong and constitutive activation of nuclear factor kappa B (NF-kappaB) is a common characteristic of MM cells. In our study we successfully target NF-kappaB with a novel NF-kappaB inhibitor dehydroxymethylepoxyquinomycin (DHMEQ). DHMEQ completely abrogates constitutive NF-kappaB activity and induces apoptosis of MM cells, whereas control peripheral blood mononuclear cells (PBMC) are resistant to NF-kappaB inhibition and apoptosis by DHMEQ treatment. DHMEQ inhibition of NF-kappaB triggers activation of caspases 8 and 9, as well as G0G1 cell cycle arrest accompanied by downregulation of antiapoptotic genes BclXL and c-FLIP and cell cycle progression gene cyclins D1 and D2. DHMEQ-mediated inhibition of vascular endothelial growth factor (VEGF) production in MM cells raises the possibility that DHMEQ abrogates the autocrine VEGF loop and enhances it; antitumor effects by inhibiting neovascularization in the bone marrow. Using an in vivo NOD/SCID/gammac(null) (NOG) mice model, we show that DHMEQ has a potent inhibitory effect on the growth of MM cells. Compared to other compounds having the potential to inhibit NF-kappaB, DHMEQ is a unique compound that blocks the translocation of NF-KB p65 into the nucleus and selectively targets NF-KB activated in tumor cells. Therefore, our study presents a new molecular target therapy in MM. (C) 2004 Wiley-Liss, Inc.