CNRS UMR 6061, Institut de Génétique et Développement, Université Rennes 1, 35043 Rennes, France.
Eur J Cancer. 2010 May;46(8):1430-7. doi: 10.1016/j.ejca.2010.01.009. Epub 2010 Mar 1.
In clear cell renal cell carcinoma (CCRCC), vascular endothelial growth factor (VEGF) represents the central positive mediator of tumour angiogenesis while VEGF receptor (VEGFR) is the primary target of anti-angiogenic therapies. TIMP3 is a physiological VEGFR-2 antagonist and thus could be considered as an anti-angiogenic factor. We therefore determined the status of this physiological inhibitor in CCRCC.
Archival tumour from 105 patients was studied. TIMP3 expression was analysed using immuno-histochemistry and real-time RT-PCR. Results were correlated with clinicopathological variables. To analyse the mechanisms of gene silencing involved, we performed Multiplex Ligation-dependent Probe Amplification (MLPA) and methylation-specific MLPA (MS-MLPA). At last, we evaluated the main upstream pathway described implicating TGFbetaRII, which induces TIMP3 expression.
A down-expression of TIMP3, determined by immunohistochemistry, affected 100/105 renal cancers (95.2%). TIMP3 mRNA levels were significantly lower in high-grade tumours. Loss of heterozygosity of the TIMP3 gene was observed in 8 tumours (7.6%) and the 5'CpG island of the TIMP3 promoter was found to be methylated in 25 tumours (23.8%). A down-expression of TGFbetaRII was found in 85/105 CCRCCs (80.9%). A significant correlation was found between TIMP3 expression and TGFbetaRII expression.
This is the first demonstration that the loss of TIMP3 expression is observed in almost all CCRCCs. This loss of expression is a common molecular event in CCRCC. It may be an important initiation step for tumour development in a complex process implicating loss of heterozygosity on chromosome 22q, promoter hyper-methylation and inactivation of the TGFbetaRII pathway.
在透明细胞肾细胞癌（ccRCC）中，血管内皮生长因子（VEGF）是肿瘤血管生成的核心正向介质，而血管内皮生长因子受体（VEGFR）则是抗血管生成治疗的主要靶点。TIMP3 是 VEGFR-2 的生理性拮抗剂，因此可以被认为是一种抗血管生成因子。我们因此确定了这种生理性抑制剂在 ccRCC 中的状态。
研究了 105 例患者的肿瘤存档标本。使用免疫组织化学和实时 RT-PCR 分析 TIMP3 的表达。结果与临床病理变量相关。为了分析涉及的基因沉默机制，我们进行了多重连接依赖性探针扩增（MLPA）和甲基化特异性 MLPA（MS-MLPA）。最后，我们评估了涉及诱导 TIMP3 表达的 TGFbetaRII 等主要上游途径。
免疫组化检测到 TIMP3 表达下调，影响了 105 例肾癌中的 100 例（95.2%）。TIMP3 mRNA 水平在高级别肿瘤中显著降低。在 8 例肿瘤中观察到 TIMP3 基因的杂合性丢失，在 25 例肿瘤中发现 TIMP3 启动子的 5'CpG 岛被甲基化。在 85/105 例 ccRCC 中发现 TGFbetaRII 表达下调。TIMP3 表达与 TGFbetaRII 表达之间存在显著相关性。
这是首次证明 TIMP3 表达缺失几乎存在于所有 ccRCC 中。这种表达缺失是 ccRCC 中的一种常见分子事件。它可能是涉及染色体 22q 杂合性丢失、启动子超甲基化和 TGFbetaRII 途径失活的肿瘤发生复杂过程中的一个重要起始步骤。
