Abstract: Objective To investigate the apoptosis-inducing effect of fucoxanthin in human prostate cancer PC-3 cells and the underlying mechanism. Methods The viability and apoptosis of PC-3 cells treated with fucoxanthin were analyzed using commercial kits, and the mitochondrial membrane potential, mitochondrial morphology and mitochondrial superoxide were detected using fluorescence probe staining. The contents of ATP, H2O2, malondialdehyde (MDA), superoxide and the total antioxidant capacity of PC-3 cells were determined. The protein expressions of Bcl-2, Bax and cytochrome c were detected with Western blotting, and the activity of caspase-9 and caspase-3/7 was detected using corresponding kits. Results Fucoxanthin significantly inhibited the viability of PC-3 cells in a time- and dose-dependent manner, and dose-dependently induced apoptosis of the cells (P<0.05). Fucoxanthin-treated PC-3 cells showed significantly decreased mitochondrial membrane potential, mitochondrial fragmentation and increased superoxide level in the mitochondria (P<0.05), and these effects of fucoxanthin were dose- dependent. Fucoxanthin dose-dependently decreased ATP level and the total antioxidant capacity of PC-3 cells, increased the contents of H2O2, MDA and superoxide (all P<0.05), enhanced the protein expressions of Bax and cytochrome c in the cytoplasm, and lowered the protein expressions of Bcl-2 and cytochromes in the mitochondria (P<0.05). Conclusions Fucoxanthin induces apoptosis of PC-3 cells by triggering mitochondrial dysfunction to cause oxidative stress and by activating mitochondria-mediated apoptotic signaling pathways, suggesting its potential in prostate cancer treatment.

Key words: fucoxanthin; prostate cancer; apoptosis; mitochondria; oxidative stress