Lipid raft cholesterol and genistein inhibit the cell viability of prostate cancer cells via the partial contribution of EGFR-Akt/p70S6k pathway and down-regulation of androgen receptor.
Soy isoflavones and cholesterol have been reported as dietary factors related to the incidence of prostate cancer. In this study, we investigated whether cell survival could be suppressed by a combination of the dispersion of lipid raft microdomains and treatment with genistein, a well-known potential isoflavone, in LNCaP prostate cancer cells. Cell viability was assayed by the property of reagent change upon reduction of resazurin to resorufin and apoptosis was evaluated by ethidium bromide/acridine orange (EB/AO) staining and PARP and caspase-3 expression. Signal transduction was investigated by immunoblot analysis. Cell viability decreased significantly more following successive double treatment with genistein and the cholesterol-lowering agent 2-hydroxypropyl-beta-cyclodextrin (HPCD) than in response to either agent alone. Apoptotic cell staining and cleavage of PARP and caspase-3 appeared more clearly in double-treated cells than in those treated with genistein alone. In cell signaling, both HPCD and genistein decreased the protein expressions of pAkt as well as the androgen receptors stimulated by EGF and DHT, respectively, in concentration-dependent manners. This pattern was also present in protein levels of pAkt and the androgen receptor located in the lipid raft fraction. Furthermore, the phosphorylation cascade of Akt, GSK-3beta and p70S6k was markedly inhibited by the combination treatment. These data suggest that prostate cancer cells could be effectively inhibited by combination treatment of cholesterol-lowering strategies and genistein. The mechanism is likely to be partially via both the EGFR-mediated Akt or p70S6k pathways and a down-regulation of androgen receptor in the lipid raft microdomain.
Oh
Hea Young
HY
Department of Urology, Urological Science Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
Leem
Jandi
J
Yoon
So Jung
SJ
Yoon
Sun
S
Hong
Sung Joon
SJ
D000073738:2-Hydroxypropyl-beta-cyclodextrin; D059002:Androgen Receptor Antagonists; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002784:Cholesterol / Q000378:metabolism*; D015536:Down-Regulation; D066246:ErbB Receptors / Q000378:metabolism; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D008297:Male; D021962:Membrane Microdomains / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000201:enzymology*; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D047392:beta-Cyclodextrins / Q000494:pharmacology*
D059002:Androgen Receptor Antagonists; D000924:Anticholesteremic Agents; D047428:Protein Kinase Inhibitors; D047392:beta-Cyclodextrins; D000073738:2-Hydroxypropyl-beta-cyclodextrin; D002784:Cholesterol; D019833:Genistein; C512478:EGFR protein, human; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa