Matrine inhibits the activity of translation factor eIF4E through dephosphorylation of 4E-BP1 in gastric MKN45 cells

Matrine, from Sophora flavescens, could remarkably inhibit tumor growth and induce apoptosis in various cancer cells in vitro. eIF4E and its inhibitor 4E-BP1 play key roles in regulating mRNA translation and cell proliferation. However, it remained elusive whether matrine inhibited cancer cells growth through attenuating the activity of 4E-BP1. In this study, we analyzed the effects of matrine on 4E-BP1 and eIF4E in gastric cancer MKN45 cells. Immunoblots showed that matrine inhibited the activity of eIF4E through dephosphorylation of 4E-BP1 in a close- and time-dependent manner. We found that matrine inactivated Erk1/2, an Upstream regulator of 4E-BP1 and eIF4E, and remarkably reduced the phosphorylation level of 4E-BP1 and eIF4E, whereas 4E-BP1 was little influenced by JNK, p38 or Akt/mTOR. Inactivation of PP2A obviously decreased the phosphorylation of 4E-BP1 in matrine-treated cells. These findings suggested that matrine inhibits the activity of eIF4E by dephosphorylating 4E-BP1, which partly counts for the growth inhibition in gastric MKN45 cells.