The transcription factor nuclear factor-kappa B (NF-κB) regulates the transcription of a number of genes involved in a variety of cellular responses, including cell survival, inflammation, and differentiation. NF-κB is activated by a variety of stimuli, proinflammatory cytokines, mitogens, growth factors, and stress-inducing agents. Aberrant NF-κB expression is considered to be one of the oncogenic factors of cancer and the constitutive activation of NF-κB is observed in several hematologic disorders [classic Hodgkin's lymphoma, diffuse large B cell lymphoma, and multiple myeloma (MM)], and the modulation of NF-κB activation is emerging as a promising novel anticancer therapeutic strategy.
Therefore, we focused on the regulation of NF-κB activation in MM. When U266 cells were treated with 6-amino-4-quinazoline, an NF-κB activation inhibitor, we determined that it most effectively blocked the interleukin (IL)-6-induced activation of MAPK and JAK/STAT pathways among different signaling inhibitors. The results of the luciferase assay indicated that 6-amino-4-quinazoline inhibited NF-κB activation with diminished NF-κB protein bound to NF-κB DNA binding sites. In addition, 6-amino-4-quinazoline suppressed the production of IL-6, which affected MM cell proliferation. Furthermore, combined treatment with bortezomib and 6-amino-4-quinazoline effectively inhibited the IL-6 and soluble IL-6R-induced activation of STAT3 and extracellular signal-regulated kinase phosphorylation. Our data showed that the inhibition of NF-κB activation abrogated MM cell proliferation induced by the IL-6 pathway, and might represent a promising therapeutic strategy for the treatment of MM.