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.
Yan
Xiaojuan
X
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.
Fraser
Michael
M
Qiu
Qing
Q
Tsang
Benjamin K
BK
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