WJ9708012 exerts anticancer activity through PKC-α related crosstalk of mitochondrial and endoplasmic reticulum stresses in human hormone-refractory prostate cancer cells.
OBJECTIVE
To investigate the anticancer mechanism of a methoxyflavanone derivative, WJ9708012, highlighting its role on a crosstalk between endoplasmic reticulum (ER) and mitochondrial stress.


METHODS
Cell proliferation was examined using sulforhodamine B assay. Cell-cycle progression, Ca(2+) mobilization and mitochondrial membrane potential (ΔΨ(m)) were detected using flow cytometric analysis. Protein expression was detected using Western blot.


RESULTS
WJ9708012 displayed an antiproliferative and apoptotic activity in human hormone-refractory prostate cancer cells with IC(50) values of 6.4 and 5.3 μmol/L in PC-3 and DU-145 cells. WJ9708012 induced a prompt increase of cytosolic Ca(2+) level and activation of protein kinase C (PKC)-α. The cleavage of μ-calpain was also induced by WJ9708012. Furthermore, WJ9708012 induced cell-cycle arrest at G(1)-phase associated with down-regulation of cyclin D1, cyclin E and cyclin-dependent kinase-4 expressions. It also caused a rapid and time-dependent decrease of phosphorylation level of mTOR (Ser(2448)), 4E-BP1 (Thr(37)/Thr(46)/Thr(70)) and p70S6K (Thr(389)), indicating the inhibition of mTOR-mediated translational pathways. The ER stress was activated by the identification of up-regulated GADD153 and glucose-regulated protein-78 protein levels. The subsequent mitochondrial stress was also identified by the observation of a decreased Bcl-2 and Bcl-xL expressions, an increased truncated Bid and Bad and a loss of ΔΨ(m).


CONCLUSIONS
WJ9708012 induces an increase of cytosolic Ca(2+) concentration and activation of PKC-α. Subsequently, a crosstalk between ER stress and mitochondrial insult is induced, leading to the inhibition of mTOR pathways and arrest of the cell-cycle at G(1) phase. The apoptosis is ultimately induced by a severe damage of mitochondrial function.
School of Pharmacy, National Taiwan University, Taipei, Taiwan, China.
Ting-chun
TC
Kuo
Wei-jan
WJ
Huang
Jih-hwa
JH
Guh
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D047309:Flavones / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
C557699:6-(3-hydroxy-3-methylbutyl)-2'-(7-hydroxy-3,7-dimethyloctyl)-3',4',5,7-tetramethoxyflavanone; D000970:Antineoplastic Agents; D047309:Flavones; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D051571:Protein Kinase C-alpha; D002118:Calcium