Methoxychalcone induces cell-cycle arrest and apoptosis in human hormone-resistant prostate cancer cells through PI 3-kinase-independent inhibition of mTOR pathways.
BACKGROUND
Chalcones are contained in fruits and vegetables, and have been suggested to display anticancer activities. In this study, the anticancer mechanism of WJ9708011 (a methoxychalcone derivative) was delineated in human prostate cancer cells.


METHODS
Cell proliferation was examined by sulforhodamine B and clonogenic assays. Cell-cycle progression and mitochondrial membrane potential (DeltaPsi(m)) were detected by flow cytometric analysis. Expressions of protein and mRNA were detected by Western blot and RT-PCR technique, respectively. The protein synthesis was examined by [(3)H]leucine incorporation assay. The overexpression or knockdown techniques for specific target protein were also used in this study.


RESULTS
WJ9708011 induced time- and concentration-dependent G1 arrest of the cell cycle and subsequent apoptosis in human prostate cancer cells. The G1-arrest effect was confirmed by down-regulated expressions of several G1-phase regulators, including cyclin D1, cyclin E, cyclin-dependent kinase (Cdk)-4, Cdk2, phospho-RB, E2F-1, and Cdc25A. The mRNA expressions of cyclin D1 and cyclin E were also inhibited through the suppression of NF-kappaB. WJ9708011 blocked the protein synthesis and inhibited mammalian target of rapamycin (mTOR) signaling pathways. The suppression of mTOR pathways were irrespective of Akt- and AMPK-activated protein kinase (AMPK), but were attributed to mitochondrial stress, in which the down-regulation of survivin protein level may play a crucial role.


CONCLUSIONS
The data suggest that WJ9708011 induces transcriptional and translational suppression of cell-cycle regulators that might be through Akt- and AMPK-independent loss of DeltaPsi(m) and inhibition of mTOR signaling pathway, leading to G1 arrest of the cell cycle and subsequent apoptotic cell death.
Sun
Yu-Wei
YW
School of Pharmacy, National Taiwan University, Taipei, Taiwan.
Huang
Wei-Jan
WJ
Hsiao
Che-Jen
CJ
Chen
Yi-Cheng
YC
Lu
Pin-Hsuan
PH
Guh
Jih-Hwa
JH
D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D047188:Chalcones / Q000494:pharmacology*; D004249:DNA Damage; D017931:DNA Primers; D004260:DNA Repair; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011471:Prostatic Neoplasms / Q000235:genetics / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D012334:RNA, Neoplasm / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D058570:TOR Serine-Threonine Kinases; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000473:pathology; D014410:Tumor Stem Cell Assay / Q000379:methods
D047188:Chalcones; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D012334:RNA, Neoplasm; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases