Objective      To determine the pro-apoptotic effect of ligustrazine (TMP) in human hormone-refractory prostate cancer (HRPC) cell line PC-3

investigate its underlying mechanism

and evaluate its effect on normal prostate epithelial cell line RWPE-1.       Methods      Different concentrations of TMP were used to treat RWPE-1 or PC-3 cells for 48 and 72 h

and then the proliferation and apoptosis in the treated cells were measured by MTT assay and Annexin V/PI assay respectively. The expression levels and phosphorylation of several key proteins in the mammalian target of rapamycin (mTOR) pathway were detected by Western blotting. The formation of eukaryotic translation initiation complex (eIF4F) was analyzed by pull-down assay with 7-methyl-GTP Sepharose 4B. The activity of cap-dependent translation was analyzed by cap-dependent reporter gene assay.       Results      TMP barely affected the proliferation and survival of RWPE-1 cells

but affected the growth and survival of PC-3 cells in dose- and time-dependent manners

and there was statistical difference when the final concentration of TMP was higher than 25 μmol/L (P0.05). Compared with the control cells (0 μmol/L)

TMP (50 or 100 μmol/L) treatment for 24 h resulted in a increase of ratio of Bax to Bcl-2 and obvious up-regulation of Caspase-3

and the treatment for 48 h induced obvious apoptosis in PC-3 cells (P0.01). Meanwhile

50 or 100 μmol/L TMP also significantly inhibited the expression of mTOR and the phosphorylation of its related downstream targets

4EBP1 and p70S6K. Furthermore

TMP reduced the formation of translation initiation complex eIF4E for cap-dependent translation through increasing the binding of 4EBP-1 with eIF4E

and thus resulted in the inhibition of cap-dependent translation and synthesis.       Conclusion      TMP reduces the cap-dependent translation of proliferative and anti-apoptotic proteins by inhibiting the activation of mTOR pathway

and thus affects the growth and survival of HRPC cells.