The University of Hong Kong, Hong Kong.
Hepatology. 2011 May;53(5):1558-69. doi: 10.1002/hep.24232.
Phosphatase and tensin homolog (PTEN) is frequently inactivated in cancers and is associated with advanced stages of cancers or metastasis. However, the molecular mechanism of PTEN in hepatocellular carcinoma (HCC) metastasis is unclear. In this study, we found frequent (47.5%, n = 40) protein underexpression of PTEN in human HCCs compared with their corresponding nontumorous livers. Significantly, PTEN underexpression was associated with larger tumor size (P = 0.021), tumor microsatellite formation (P = 0.027), and shorter overall survival of patients (P = 0.035). Using different cell models, we observed that PTEN-knockdown HCC cells and PTEN-knockout mouse embryonic fibroblasts (MEFs) had enhanced cell migratory and invasive abilities. In addition to activation of AKT, there was up-regulation of the Sp1 transcription factor (SP1) and matrix metalloproteinase 2 (MMP2), as well as MMP2 activation in PTEN-knockdown HCC cells and PTEN(-/-) MEFs. With dual luciferase reporter assay, exogenous expression of SP1 in HCC cells led to enhanced MMP2 promoter activity by up to 74%, whereas deletion of the putative SP1 binding site on the MMP2 promoter led to reduced promoter activity by up to 65%. Using chromatin immunoprecipitation assay, we documented increased binding of SP1 to the MMP2 promoter in PTEN-knockdown HCC cells. Overexpression of SP1 and MMP2 was significantly but negatively associated with PTEN underexpression in human HCCs.
Our results show that PTEN was underexpressed in HCCs, and this underexpression was associated with more aggressive biological behavior and poorer patient survival. We have provided the first evidence that MMP2 up-regulation upon PTEN loss is SP1-dependent. Our findings indicate that PTEN plays a significant role in down-regulating HCC cell invasion via the AKT/SP1/MMP2 pathway.
磷酸酶和张力蛋白同源物（PTEN）在癌症中经常失活，与癌症的晚期或转移有关。然而，PTEN 在肝细胞癌（HCC）转移中的分子机制尚不清楚。在这项研究中，我们发现与相应的非肿瘤性肝脏相比，人 HCC 中 PTEN 的蛋白表达水平经常（47.5%，n=40）降低。重要的是，PTEN 表达降低与肿瘤体积较大（P=0.021）、肿瘤微卫星形成（P=0.027）以及患者总体生存时间较短（P=0.035）有关。使用不同的细胞模型，我们观察到 PTEN 敲低 HCC 细胞和 PTEN 敲除的小鼠胚胎成纤维细胞（MEFs）具有增强的细胞迁移和侵袭能力。除了 AKT 的激活外，PTEN 敲低 HCC 细胞和 PTEN（-/-）MEFs 中 Sp1 转录因子（SP1）和基质金属蛋白酶 2（MMP2）的上调以及 MMP2 的激活。通过双荧光素酶报告基因检测，外源性表达 SP1 可使 HCC 细胞中的 MMP2 启动子活性增强高达 74%，而 MMP2 启动子上假定的 SP1 结合位点缺失可使启动子活性降低高达 65%。通过染色质免疫沉淀检测，我们记录到在 PTEN 敲低 HCC 细胞中 SP1 与 MMP2 启动子的结合增加。SP1 和 MMP2 的过表达与 HCC 中 PTEN 表达降低显著但呈负相关。
我们的结果表明，PTEN 在 HCC 中表达降低，这种降低与更具侵袭性的生物学行为和更差的患者生存相关。我们首次提供了证据表明，PTEN 缺失时 MMP2 的上调依赖于 SP1。我们的研究结果表明，PTEN 通过 AKT/SP1/MMP2 通路在下调 HCC 细胞侵袭中起重要作用。
