Ligustrazine Suppresses the Growth of HRPC Cells through the Inhibition of Cap- Dependent Translation Via Both the mTOR and the MEK/ERK Pathways

Anticancer Agents Med Chem. 2015;15(6):764-72. doi: 10.2174/1871520615666150305112120.

Abstract

Ligustrazine (TMP) has recently been used for the treatment of various cancers. However, its exact mechanisms of action, particularly the functions and the mechanisms of Ligustrazine in human hormone-refractory prostate cancer (HRPC), have not yet been extensively studied. Recently, our findings suggest that Ligustrazine dose- and time-dependently inhibits the growth of HRPC cells by reducing their proliferation and promoting apoptosis. Interestingly, the treatment of hormone-refractory prostate cancer (PC-3) cells with Ligustrazine results in a significant inhibition of the activation of mTOR and related downstream targets, which are critical for cell growth. Furthermore, pull-down assays with 7-methyl- GTP Sepharose 4B beads indicate that Ligustrazine reduces the available eIF4E for translation initiation. Accordingly, the results from the translation assay using a luciferase reporter system further demonstrate that Ligustrazine indeed inhibits cap-dependent translation. In addition, the transient overexpression of eIF4E or MNK1 prevents the Ligustrazine-induced inhibition of proliferation and confers significant protection against Ligustrazine-induced apoptosis. Therefore, the present study provides evidences that Ligustrazine may be a candidate for therapeutic reagent for the treatment of HRPC and certifies that Ligustrazine modulates the availability of eIF4E mainly through the mTOR and MEK/ERK signaling pathways to inhibit cap-dependent translation. Taken together, our results indicate that the inhibition of cap-dependent translation is likely an essential mechanism in Ligustrazine-induced apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Cell Line, Tumor
  • Cell Proliferation / drug effects*
  • Cell Proliferation / genetics
  • Eukaryotic Initiation Factor-4E / genetics
  • Humans
  • MAP Kinase Signaling System / drug effects*
  • MAP Kinase Signaling System / genetics*
  • Male
  • Phosphorylation / drug effects
  • Phosphorylation / genetics
  • Prostatic Neoplasms / drug therapy
  • Prostatic Neoplasms / genetics
  • Protein Biosynthesis / drug effects*
  • Protein Biosynthesis / genetics
  • Pyrazines / pharmacology*
  • Signal Transduction / drug effects*
  • Signal Transduction / genetics
  • TOR Serine-Threonine Kinases / genetics*

Substances

  • Eukaryotic Initiation Factor-4E
  • Pyrazines
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • tetramethylpyrazine