How can food extracts consumed in the Mediterranean and East Asia suppress prostate cancer proliferation?

We have developed a blend of food extracts commonly consumed in the Mediterranean and East Asia, named blueberry punch (BBP), with the ultimate aim to formulate a chemoprevention strategy to inhibit prostate cancer progression in men on active surveillance protocol. We demonstrated previously that BBP inhibited prostate cancer cell proliferation in vitro and in vivo. The purpose of this study was to determine the molecular mechanism responsible for the suppression of prostate cancer cell proliferation by BBP. Treatment of lymph node-metastasised prostate cancer cells (LNCaP) and bone-metastasised prostate cancer cells (PC-3 and MDA-PCa-2b) with BBP (up to 0·8 %) for 72 h increased the percentage of cells at the G0/G1 phase and decreased those at the S and G2/M phases. The finding was supported by the reduction in the percentage of Ki-67-positive cells and of DNA synthesis measured by the incorporation of 5-ethynyl-2"²-deoxyuridine. Concomitantly, BBP treatment decreased the protein levels of phosphorylated retinoblastoma, cyclin D1 and E, cyclin-dependent kinase (CDK) 4 and 2, and pre-replication complex (CDC6 and MCM7) in LNCaP and PC-3 cells, whereas CDK inhibitor p27 was elevated in these cell lines. In conclusion, BBP exerts its anti-proliferative effect on prostate cancer cells by modulating the expression and phosphorylation of multiple regulatory proteins essential for cell proliferation.