Bruton's agammaglobulinemia tyrosine kinase (Btk) regulates TPA‑induced breast cancer cell invasion via PLCγ2/PKCβ/NF‑κB/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‑κB (NF‑κB) 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‑ ‑tetradecanoylphorbol‑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 µM), CNX‑774 (10 µM)] significantly attenuated TPA‑induced cell invasion and migration in MCF‑7 cells and inhibited the activation of the phospholipase Cγ2/PKCβ 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 IκB kinase/NF‑κB/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.