Over-expression of PTEN sensitizes human ovarian cancer cells to cisplatin-induced apoptosis in a p53-dependent manner.
OBJECTIVE
Resistance to cisplatin-centered chemotherapy is a major cause of treatment failure in human ovarian cancer. Whereas PTEN, a tumor suppressor gene product, is believed to promote apoptosis primarily via inactivation of the PI3K/Akt cell survival pathway, recent evidence suggests that PTEN may function independently of this pathway. Activation of p53 is a key determinant of sensitivity to cisplatin-induced apoptosis. Whether PTEN can facilitate cisplatin sensitivity, and this involves the activation of p53, remains unclear. In this study, we determined whether and how PTEN over-expression sensitizes ovarian cancer cells to CDDP-induced apoptosis.


RESULTS
Using pairs of chemosensitive and chemoresistant ovarian cancer cell lines (OV20028 vs. C13* and A2780-s vs. A2780-cp) as an in vitro model, we have examined the influence of PTEN over-expression in regulation of cisplatin-induced apoptosis. Apoptosis was assessed morphologically by Hoechst staining and confirmed by the detection of cleaved products of caspase-3 and PARP by Western blot. Over-expression of PTEN by PTEN cDNA transfection up-regulates p53 content and increases the sensitivity of chemoresistant cells to cisplatin-induced apoptosis without detectable changes in the levels of phosphorylated Akt and FKHR as well as FasL mRNA abundance as determined by Western blot and RT-PCR, respectively. PTEN-mediated chemosensitization was attenuated by p53 down-regulation by siRNA in C13*, a chemoresistant wild-type p53 cell. Moreover, PTEN over-expression failed to sensitize the chemoresistant p53 mutant ovarian cancer cell line A2780-cp to cisplatin-induced apoptosis, unless wild-type p53 was reconstituted by adenoviral p53 infection.


CONCLUSIONS
Taken together, these data suggest that PTEN over-expression may represent a novel therapeutic approach for chemoresistant human ovarian cancer and that this may involve a p53-mediated apoptotic cascade independent of the PI3K/Akt pathway.
Reproductive Biology Unit and Division of Gynecologic Oncology, Department of Obstetrics and Gynaecology, University of Ottawa, Ottawa Health Research Institute, 725 Parkdale Avenue, Ottawa, Ontario, Canada, K1Y 4E9.
Xiaojuan
X
Yan
Michael
M
Fraser
Qing
Q
Qiu
Benjamin K
BK
Tsang
D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D053222:Fas Ligand Protein; D005260:Female; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000378:metabolism; D015316:Genetic Therapy / Q000379:methods; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051059:PTEN Phosphohydrolase / Q000096:biosynthesis* / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D014162:Transfection; D048069:Tumor Necrosis Factors / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000378:metabolism*
C505661:FASLG protein, human; C085126:FOXO1 protein, human; D053222:Fas Ligand Protein; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; D008562:Membrane Glycoproteins; C495901:TP53 protein, human; D048069:Tumor Necrosis Factors; D016159:Tumor Suppressor Protein p53; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D002945:Cisplatin