P53 enhances ascorbyl stearate-induced G2/M arrest of human ovarian cancer cells.
BACKGROUND
Ascorbyl stearate (Asc-S) is a synthetic ester of ascorbic acid that has been shown to significantly reduce the mutagenic effects of alkylating agents and hepatocarcinogenesis in vivo. We have previously demonstrated that Asc-S inhibits ovarian carcinoma cell proliferation through modulation of the cell cycle. This study was designed to further elucidate the mechanisms underlying such regulation.


METHODS
Wild type p53-expressing cell lines (Ov2008 and C13) were used to evaluate the contributions of p53 to Asc-S-induced G2/M arrest. Cell cycle analysis was performed by flow cytometry. Variation of p53, p21, and GADD45 was evaluated by Western blot and RT-PCR. Knockdown of endogenous p53 was achieved by siRNA.


RESULTS
The expression of p53 downstream genes, p21 and GADD45 was upregulated whereas 14-3-3sigma was unaffected. Phosphorylation of Cdc2 at residue tyrosine-15 was also induced by Asc-S treatment. However, pSilencer-p53-siRNA only partially rescued the Asc-S induced G2/M arrest.


CONCLUSIONS
These data show that the anti-proliferative activity of Asc-S on ovarian cancer cells is due in part to G2/M arrest modulated by a p53-dependent pathway.
Naidu
K Akhilender
KA
Division of Anatomic Pathology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA.
Fang
Quan
Q
Naidu
Kamatham A
KA
Cheng
Jin Q
JQ
Nicosia
Santo V
SV
Coppola
Domenico
D
D001205:Ascorbic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D034741:RNA, Small Interfering / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D015854:Up-Regulation; D000097642:GADD45 Proteins
D001205:Ascorbic Acid; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; C493956:CDKN1A protein, human; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C495901:TP53 protein, human; C036225:ascorbyl monostearate