Vitexicarpin Induces Apoptosis In Human Prostate Carcinoma PC-3Cells Through G2/M Phase Arrest

Prostate cancer is the second most common diagnosed cancer after lung cancerworldwide, and it is the third most common cause of cancer deaths in developed countries inman. In2012, about241,704men were diagnosed with prostate cancer and28,170men diedof it as estimated by the American Cancer Society. Treatment of prostate cancer depends onage of patients, overall health of individual, and the stage of disease. Current availabletherapies include active surveillance, surgery, radiation therapy, hormone therapy andchemotherapy. However, because prostate cancer can recur in an androgen independentprostate cancer that is lack of effective therapies, the mortality rate associated with recurrentcases is high. There is great demand for effective novel therapeutic agents.Vitexicarpin (3’,5-dihydroxy-3,4’,6,7-tetramethoxyflavone), a polymethoxyflavoneisolated from Viticis Fructus (Vitex rotundifolia Linne fil.), has long been used as ananti-inflammatory herb in traditional Chinese medicine. It has also been reported thatvitexicarpin induces growth inhibition, cell cycle arrest, and apoptosis in various cancer cellsincluding the human cervical cancer cell line Hela, hepatocellular carcinoma cell line HepG2,lung epithelial cell line A549and leukemic cell line K562. However, there is no reportelucidating its effect on human prostate carcinoma cells.The aim of the present study was to examine the apoptotic induction activity ofvitexicarpin on androgen independent prostate cancer PC-3cells and molecular mechanismsinvolved in the activity. MTT study showed that vitexicarpin dose-dependently inhibitedgrowth of PC-3cells with IC50~28.78μM. Cytotoxicity assay with trypan blue showed thatvitexicarpin has little cytotoxicity on mouse spleen cells. Hoechst33258staining analysisrevealed that nuclear shrinkage and DNA fragmentation on PC-3cells. The effect ofvitexicarpin on PC-3cells apoptosis was tested using prodium iodide (PI)/Annexin V-FITCdouble staining and flow cytometry. The results indicated that vitexicarpin significantlyinduced apoptotic cell death in PC-3cells with dose-dependent way. PI staining was showedthat vitexicarpin arrest PC-3cell cycle at G2/M phase. DCFH-DA staining was showed thatROS levels in PC-3cells were significantly increased. Rhodamine123staining was showeddecrease in mitochondrial membrane potential in PC-3cells. Furthermore, Western blottinganalysis demonstrated that vitexicarpin induced PC-3cell apoptosis was associated withupregulation of the proapoptotic protein Bax, and downregulation of antiapoptotic protein Bcl-2, release of Cytochrome c from mitochondria and activation of Caspase-3. Vitexicarpinalso decreased the expression of cell cycle protein CDK1and Cyclin B1.In conclusion, Vitexicarpin can significantly induced the apoptosis in PC-3cells andhave no cytotoxicity on normal cells. Our findings suggested that vitexicarpin may become apotential leading drug in the therapy of prostate carcinoma.