Cyclic bisbibenzyls induce growth arrest and apoptosis of human prostate cancer PC3 cells

Aim: To investigate the cytotoxic effects of four cyclic bisbibenzyls, Riccardin C (Ric), Pakyonol (Pak), Marchantin M (Mar), and Plagiochin E (Pla) against chemoresistant prostate cancer PC3 cells. Methods: Cell growth was assayed by MTT method, and apoptotic related protein Bcl-2 and Bax, poly(ADP-ribose) polymerase (PARP) were examined by Western blotting. Cell cycle and apoptosis of PC3 cells were evaluated with flow cytometry and morphologic examinations. Results: The four compounds inhibited proliferation and elicited cell death in a dose-and time-dependent manner with IC50 values of 3.22 mu mol/L for Ric, 7.98 mu mol/L for Pak, 5.45 mu mol/L for Mar, and 5.99 mu mol/L for Pla, respectively. Furthermore, exposed to these chemicals caused a decrease in the antiapoptotic protein Bcl-2 and an increase in proapoptotic Bax expression. PARP cleavage and caspase-3 activity were also observed. Conclusion: The results suggest that cyclic bisbibenzyls could be used for the development of novel therapeutic chemicals against prostate cancer.