Department of Obstetric and Gynecology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwa.
Mol Cancer. 2009 Dec 11;8:120. doi: 10.1186/1476-4598-8-120.
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.
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.
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.
胰岛素样生长因子结合蛋白（IGFBP-3）是一种具有抗增殖、促凋亡和抑制侵袭作用的蛋白，其转录受到 p53 的调控。启动子甲基化与基因沉默和癌症进展有关。我们通过免疫组织化学染色和定量甲基化特异性 PCR（qMSP）研究了卵巢子宫内膜样癌（OEC）中 IGFBP-3 与 p53 表达以及 IGFBP-3 启动子甲基化的相关性。此外，我们使用 OEC 的两个亚系 OVTW59-P0（低侵袭性）和 P4（高侵袭性）亚系评估了野生型（wt）p53 对 IGFBP-3 表达的分子调控机制。
在 60 例 OEC 中，40.0%的 IGFBP-3 表达较低，与 IGFBP-3 启动子甲基化程度较高显著相关。35.0%的 OEC 中存在 p53 过表达，但与临床结局和 IGFBP-3 无关。通过 Kaplan-Meier 分析，IGFBP-3 表达较低、IGFBP-3 启动子甲基化程度较高、p53 正常的患者生存率最低。在 OEC 细胞系中，IGFBP-3 表达与 IGFBP-3 启动子甲基化相关。用 DNA 甲基转移酶抑制剂（5-氮杂脱氧胞苷）处理后，IGFBP-3 表达得到恢复，用 p53 抑制剂（pifithrin-α）处理后，IGFBP-3 表达受到抑制。在 IGFBP-3 启动子的转录起始点上游-210、-206、-183 和-179 位发现了假定的 p53 调节位点。这些位点的定向突变定量降低了 IGFBP-3 的转录活性。
我们的数据表明，在不存在 p53 过表达的情况下，IGFBP-3 启动子甲基化导致 IGFBP-3 沉默与癌症进展有关。这些结果支持 IGFBP-3 甲基化在 OEC 癌变中的潜在作用。
