Promoter methylation of IGFBP-3 and p53 expression in ovarian endometrioid carcinoma.
BACKGROUND
Insulin-like growth factor binding protein (IGFBP-3) is an antiproliferative, pro-apoptotic and invasion suppressor protein which is transcriptionally regulated by p53. Promoter methylation has been linked to gene silencing and cancer progression. We studied the correlation between IGFBP-3 and p53 expression as well as IGFBP-3 promoter methylation in ovarian endometrioid carcinoma (OEC) by immunohistochemical staining and quantitative methylation-specific PCR (qMSP). Additionally, we assessed the molecular regulatory mechanism of wild type (wt) p53 on IGFBP-3 expression using two subclones of OEC, the OVTW59-P0 (low invasive) and P4 (high invasive) sublines.


RESULTS
In 60 cases of OEC, 40.0% showed lower IGFBP-3 expression which was significantly correlated with higher IGFBP-3 promoter methylation. p53 overexpression was detected in 35.0% of OEC and was unrelated to clinical outcomes and IGFBP-3. By Kaplan-Meier analysis, patients with lower IGFBP-3, higher IGFBP-3 promoter methylation, and normal p53 were associated most significantly with lower survival rates. In OEC cell line, IGFBP-3 expression was correlated with IGFBP-3 promoter methylation. IGFBP-3 expression was restored after treatment with a DNA methy-transferase inhibitors (5-aza-deoxycytidine) and suppressed by a p53 inhibitor (pifithrin-alpha). The putative p53 regulatory sites on the promoter of IGFBP-3 were identified at -210, -206, -183 and -179 bases upstream of the transcription start site. Directed mutagenesis at these sites quantitatively reduced the transcription activity of IGFBP-3.


CONCLUSIONS
Our data suggests that IGFBP-3 silencing through IGFBP-3 promoter methylation in the absence of p53 overexpression is associated with cancer progression. These results support a potential role of IGFBP-3 methylation in the carcinogenesis of OEC.
Torng
Pao-Ling
PL
Department of Obstetric and Gynecology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwa. pltorng@ntu.edu.tw
Lin
Ching-Wei
CW
Chan
Michael Wy
MW
Yang
Hui-Wen
HW
Huang
Su-Cheng
SC
Lin
Chin-Tarng
CT
D000328:Adult; D018269:Carcinoma, Endometrioid / Q000235:genetics*; D019175:DNA Methylation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics*; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000235:genetics*; D011401:Promoter Regions, Genetic; D015996:Survival Rate; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
D018972:Insulin-Like Growth Factor Binding Protein 3; D016159:Tumor Suppressor Protein p53