Tubocapsanolide A inhibits transforming growth factor-β-activating kinase 1 to suppress NF-κB-induced CCR7

Withanolides are C₂₈ steroidal lactones isolated from plants that exhibit potent anti-cancer activity. The chemokine receptor CCR7 is important for lymphatic invasion of cancer cells and is overexpressed in metastatic breast cancer cells. A bioactive withanolide tubocapsanolide A (Tubo A) suppressed NF-κB-mediated CCR7 expression in breast cancer cells and attenuated their migration toward lymphatic endothelial cells. Chromatin immunoprecipitation assay confirmed that binding of NF-κB to the consensus site localized at the -398/-389 of human CCR7 promoter was repressed by Tubo A. Tubo A inhibited IκB kinase (IKK) and p38 kinase and downstream mitogen and stress-activated protein kinase 1 (MSK1) activity to reduce IκB degradation and to suppress NF-κB activation. Co-expression of IKK and MSK1 fully rescued Tubo A-induced inhibition. In addition, ectopic expression of transforming growth factor-β-activating kinase (TAK1), the common upstream kinase of IKK and MSK1, also completely reversed the inhibition by Tubo A. Most importantly, Tubo A reduced NF-κB activation, CCR7 expression, and lymph node metastasis of breast cancer in vivo. We conclude that Tubo A inhibits TAK1 to repress NF-κB-induced CCR7 expression in breast cancer cells and suggest that Tubo A may be useful for the prevention of lymphatic invasion of breast cancer cells.