Down-regulation of peroxisome proliferator-activated receptor gamma in human cervical carcinoma.
OBJECTIVE
Peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the nuclear hormone receptor superfamily. Treatment of PPARgamma ligands has been shown to inhibit the growth of various human cancer cells. However, it has not been reported whether human cervical carcinoma cells express PPARgamma. In this study, we investigated the expression of PPARgamma in human normal cervix and cervical carcinoma tissues, and as well as the effect of PPARgamma ligands on cervical cancer cells survival.


METHODS
Fresh cervical tissues from a study group of 10 study patients diagnosed with cervical carcinoma were analyzed for the expression of PPARgamma using real-time RT-PCR and Western blot analysis. Immunohistochemical staining for PPARgamma was also performed on the serial sections of 40 cervical carcinomas. In addition, we evaluated the feasibility of PPARgamma ligands, as a potential therapeutic drug against cervical cancer cells using MTT assay and FACS analysis.


RESULTS
We found that there were lower expression levels of PPARgamma mRNA and protein in cervical carcinoma tissues than in normal cervical tissues. The extent and intensity of immunoreactive PPARgamma in normal cervix tissues were statistically much greater than those of carcinoma tissues. In order to study effects of PPAR ligand on cell proliferation, we chose ciglitizone that showed very potent growth inhibitory effects on the proliferation of two human cervical cancer cell lines (C-33-A and C-4II). C-4II cells express high expression of PPARgamma, while C-33A cells express low level of PPARgamma. Treatment with ciglitizone inhibited the growth of C-4II cells in a dose-dependent manner, while the growth inhibitory effect of ciglitizone was much less in C-33A cells. In order to test whether ciglitizone-induced growth suppressive effects on cervical cancer cell lines is PPAR-dependent, we treated cervical cancer cells with ciglitizone and/or GW9662 (a PPARgamma antagonist). No significant difference in cell survival was found in cells treated with ciglitizone alone vs. co-treated with ciglitizone and GW9662. GW9662 alone did not induce any cell growth arrest in the cells that we used (data not shown). Thus, we concluded that growth suppressive effects by ciglitizone may not be dependent upon status of PPAR expression. To clarify the mechanism by which ciglitizone inhibits the growth of cervical carcinoma cells, flow cytometry and Western blotting assay were performed. As results, we demonstrated that a large portion of C-4II cells (but not in C-33A) after ciglitizone treatment were arrest at G1 phase with the induction of p21(Cip1/Waf1) and p27(kip1) protein.


CONCLUSIONS
These results suggest that PPARgamma is down-regulated in multiple human cervical cancer tissues and cell lines. Ciglitizone may suppress human cervical cancer cells in PPAR-independent manner.
Jung
Tae-Il
TI
Department of Obstetrics and Gynecology, School of Medicine, Keimyung University, 194 Dongsan-Dong, Choong-Ku, Daegu, Korea.
Baek
Won-Ki
WK
Suh
Seong-Il
SI
Jang
Byeong-Churl
BC
Song
Dae-Kyu
DK
Bae
Jae-Hoon
JH
Kwon
Kun-Young
KY
Bae
Ji-Hyun
JH
Cha
Soon-Do
SD
Bae
Insoo
I
Cho
Chi-Heum
CH
D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015536:Down-Regulation; D005260:Female; D016193:G1 Phase / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D008024:Ligands; D047495:PPAR gamma / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D045162:Thiazolidinediones / Q000494:pharmacology; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology
C493956:CDKN1A protein, human; C436291:CDKN1B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D047495:PPAR gamma; D012333:RNA, Messenger; D045162:Thiazolidinediones; D050760:Cyclin-Dependent Kinase Inhibitor p27; C039671:ciglitazone