Program in Urosciences, Division of Urology, Department of Surgery, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA.
J Biol Chem. 2012 Aug 24;287(35):29968-78. doi: 10.1074/jbc.M112.379396. Epub 2012 Jul 2.
Emerging evidence suggests that the SAM pointed domain containing ETS transcription factor (SPDEF) plays a significant role in tumorigenesis in prostate, breast, colon, and ovarian cancer. However, there are no in vivo studies with respect to the role of SPDEF in tumor metastasis. The present study examined the effects of SPDEF on tumor cell metastasis using prostate tumor cells as a model. Utilizing two experimental metastasis models, we demonstrate that SPDEF inhibits cell migration and invasion in vitro and acts a tumor metastasis suppressor in vivo. Using stable expression of SPDEF in PC3-Luc cells and shRNA-mediated knockdown of SPDEF in LNCaP-Luc cells, we demonstrate for the first time that SPDEF diminished the ability of disseminated tumors cells to survive at secondary sites and establish micrometastases. These effects on tumor metastasis were not a result of the effect of SPDEF on cell growth as SPDEF expression had no effect on cell growth in vitro or subcutaneous tumor xenograft-growth in vivo. Transcriptional analysis of several genes associated with tumor metastasis, invasion, and the epithelial-mesenchymal transition demonstrated that SPDEF expression selectively down-regulated MMP9 and MMP13 in prostate cancer cells. Further analysis indicated that forced MMP9 or MMP13 expression rescued the invasive phenotype in SPDEF expressing PC3 cells in vitro, suggesting that the effects of SPDEF on tumor invasion are mediated, in part, through the suppression of MMP9 and MMP13 expression. These results demonstrate for the first time, in any system, that SPDEF functions as a tumor metastasis suppressor in vivo.
新出现的证据表明，富含 SAM 结构域的 ETS 转录因子（SPDEF）在前列腺癌、乳腺癌、结肠癌和卵巢癌的肿瘤发生中发挥重要作用。然而，目前还没有关于 SPDEF 在肿瘤转移中的作用的体内研究。本研究以前列腺肿瘤细胞为模型，探讨了 SPDEF 对肿瘤细胞转移的影响。利用两种实验性转移模型，我们证明 SPDEF 在体外抑制细胞迁移和侵袭，并在体内作为肿瘤转移抑制因子发挥作用。利用 SPDEF 在 PC3-Luc 细胞中的稳定表达和 shRNA 介导的 SPDEF 在 LNCaP-Luc 细胞中的敲低，我们首次证明 SPDEF 降低了播散肿瘤细胞在次级部位存活和建立微转移的能力。这些对肿瘤转移的影响不是 SPDEF 对细胞生长的影响的结果，因为 SPDEF 表达对体外细胞生长或体内皮下肿瘤异种移植生长没有影响。对与肿瘤转移、侵袭和上皮-间充质转化相关的几个基因的转录分析表明，SPDEF 表达选择性地下调了前列腺癌细胞中的 MMP9 和 MMP13。进一步的分析表明，强制表达 MMP9 或 MMP13 可挽救 SPDEF 表达的 PC3 细胞的侵袭表型，表明 SPDEF 对肿瘤侵袭的影响部分是通过抑制 MMP9 和 MMP13 的表达来介导的。这些结果首次证明，在任何系统中，SPDEF 在体内均作为肿瘤转移抑制因子发挥作用。
