Bruton's agammaglobulinemia tyrosine kinase (Btk) regulates TPA-induced breast cancer cell invasion via PLC[gamma]2/PKC[beta]/NF-[kappa]B/AP-1-dependent matrix metalloproteinase-9 activation

Bruton's agammaglobulinemia tyrosine kinase (BTK) is an important cytoplasmic tyrosine kinase involved in B-lymphocyte development, differentiation, and signaling. Activated protein kinase C (PKC), in turn, induces the activation of mitogen-activated protein kinase (MAPK) signaling, which promotes cell proliferation, viability, apoptosis, and metastasis. This effect is associated with nuclear factor-[kappa]B (NF-[kappa]B) activation, suggesting an anti-metastatic effect of BTK inhibitors on MCF-7 cells that leads to the downregulation of matrix metalloproteinase (MMP)-9 expression. However, the effect of BTK on breast cancer metastasis is unknown. In this study, the anti-metastatic activity of BTK inhibitors was examined in MCF-7 cells focusing on MMP-9 expression in 12-O-tetrade canoylphorbol-13-acetate (TPA)-stimulated MCF-7 cells. The expression and activity of MMP-9 in MCF-7 cells were investigated using quantitative polymerase chain reaction analysis, western blotting, and zymography. Cell invasion and migration were investigated using the Matrigel invasion and cell migration assays. BTK inhibitors [ibrutinib (10 [micro]M), CNX-774 (10 [micro]M)] significantly attenuated TPA-induced cell invasion and migration in MCF-7 cells and inhibited the activation of the phospholipase C[gamma]2/PKC[beta] signaling pathways. In addition, small interfering RNA specific for BTK suppressed MMP-9 expression and cell metastasis. Collectively, results of the present study indicated that BTK suppressed TPA-induced MMP-9 expression and cell invasion/migration by activating the MAPK or I[kappa]B kinase/NF-[kappa]B/activator protein-1 pathway. The results clarify the mechanism of action of BTK in cancer cell metastasis by regulating MMP-9 expression in MCF-7 cells. Key words: Bruton's agammaglobulinemia tyrosine kinase, matrix metalloproteinase-9, protein kinase C, MCF-7 cells, neoplasm invasiveness