The present study examined the anti-proliferative effects of
piplartine on the human
prostate cancer cell line PC-3. This is the first report demonstrating the
piplartine anti-
cancer activity toward
prostate cancer cell lines, although its precise mechanism of action is still not completely defined. In MTT assays, it preferentially inhibited growth of
androgen-independent PC-3 cells in a dose-dependent (3-30 microM) and time-dependent (12-48 h) manner. In PC-3 cells, it showed an IC50 of 15 microM after 24 h of treatment. After a 24-30 microM treatment for 24 h, there were some reduction of cell volume, cell vacuolization,
chromatin condensation and increased number of apoptotic cells visible by light and fluorescence microscopy.
Agarose gel electrophoresis revealed that cells treated with
piplartine exhibited DNA fragmentation. In addition, growth inhibition of PC-3 cells was associated with G2/M arrest and sub-G1 accumulation. Higher concentrations (24-30 microM) of
piplartine modulated apoptosis-related
protein expression by down-regulating cdc-2 expression and up-regulating PARP/
procaspase-3 cleavage. Also, PC-3 cells treated with
piplartine demonstrated
caspase-3 activation, as observed with an in vitro
caspase-3 colorimetric assay kit. Taken together, these results demonstrated that high concentrations of
piplartine exhibited anti-proliferative and anti-
cancer effects on PC-3 cells and that caspase-3-mediated PARP cleavage and cell cycle arrest at G2/M phase are involved in the underlying cellular mechanism of the apoptosis process.