Activation of PI3K/Akt pathway by PTEN reduction and PIK3CA mRNA amplification contributes to cisplatin resistance in an ovarian cancer cell line.
OBJECTIVE
The aim of this study was to understand the role of PIK3CA and PTEN on the resistance of human ovarian cancer cells to cisplatin-induced apoptosis.


METHODS
Human ovarian cancer cell OVCAR-3 and cisplatin-resistant subclone OVCAR-3/CDDP cells were used for these studies. The expressions of apoptosis regulating proteins and PI3K/Akt signaling proteins were systematically examined.


RESULTS
OVCAR-3/CDDP cells were 4.8-fold more resistant to cisplatin compared to OVCAR-3 cells following 72 h exposure to this drug. This resistance was paralleled with reduced susceptibility to cisplatin-induced apoptosis. Apoptotic proteins were differentially expressed in OVCAR-3/CDDP cells, resulting in the inhibition of Bax translocalization. Cisplatin inhibited Akt phosphorylation and activation in OVCAR-3 cells but not in OVCAR-3/CDDP cells. The specific PI3K inhibitors LY294002 and wortmannin sensitized OVCAR-3/CDDP cells to cisplatin-induced apoptosis and decreased cell viability. A low level of PTEN expression was strongly associated with amplified PIK3CA and PI3K/Akt activities in OVCAR-3/CDDP cells. Small interfering RNA knockdown of PTEN and the expression of active p110alpha resulted in a blockade of apoptosis by cisplatin in OVCAR-3 cells.


CONCLUSIONS
These results collectively indicate that the development of resistance in OVCAR-3 cells was derived by increased PIK3CA transcription and reduction of PTEN expression. These alterations conferred cisplatin resistance to cisplatin through the activation of PI3K/Akt and the inhibition of Bax translocation.
Lee
Sooyong
S
Bioanalysis and Biotransformation Research Center, Korea Institute of Science and Technology, Seoul 136-791, South Korea.
Choi
Eui-Ju
EJ
Jin
Changbae
C
Kim
Dong-Hyun
DH
D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000235:genetics*; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D058534:Class I Phosphatidylinositol 3-Kinases; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D005260:Female; D005784:Gene Amplification; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
D014408:Biomarkers, Tumor; D002945:Cisplatin; D058534:Class I Phosphatidylinositol 3-Kinases; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C484760:PIK3CA protein, human; C494918:AKT1 protein, human; C494929:PTEN protein, human