Adler David, Offermann Anne, Braun Martin, Menon Roopika, Syring Isabella, Nowak Michael, Halbach Rebecca, Vogel Wenzel, Ruiz Christian, Zellweger Tobias, Rentsch Cyrill A, Svensson Maria, Andren Ove, Bubendorf Lukas, Biskup Saskia, Duensing Stefan, Kirfel Jutta, Perner Sven
Endocr Relat Cancer. 2014 Aug;21(4):663-675. doi: 10.1530/ERC-14-0171. Epub 2014 Jun 17.
In a recent effort to unravel the molecular basis of prostate cancer (PCa), Barbieri and colleagues using whole-exome sequencing identified a novel recurrently mutated gene, MED12, in 5.4% of primary PCa. MED12, encoding a subunit of the Mediator complex, is a transducer of Wnt/β-catenin signaling, linked to modulation of hedgehog signaling and to the regulation of transforming growth factor beta (TGFβ)-receptor signaling. Therefore, these studies prompted us to investigate the relevance of MED12 in PCa. Expression of MED12, SMAD3 phosphorylation, and proliferation markers was assessed by immunohistochemistry on tissue microarrays from 633 patients. siRNA-mediated knockdown of MED12 was carried out on PCa cell lines followed by cellular proliferation assays, cell cycle analysis, apoptosis assays, and treatments with recombinant TGFβ3. We found nuclear overexpression of MED12 in 40% (28/70) of distant metastatic castration-resistant prostate cancer (CRPC(MET)) and 21% (19/90) of local-recurrent CRPC (CRPC(LOC)) in comparison with frequencies of less than 11% in androgen-sensitive PCa, and no overexpression in benign prostatic tissues. MED12 expression was significantly correlated with high proliferative activity in PCa tissues, whereas knockdown of MED12 decreased proliferation, reduced G1- to S-phase transition, and increased the expression of the cell cycle inhibitor p27. TGFβ signaling activation associates with MED12 nuclear overexpression in tissues and results in a strong increase in MED12 nuclear expression in cell lines. Furthermore, MED12 knockdown reduced the expression of the TGFβ target gene vimentin. Our findings show that MED12 nuclear overexpression is a frequent event in CRPC in comparison with androgen-sensitive PCa and is directly implicated in TGFβ signaling.
在最近一项旨在揭示前列腺癌（PCa）分子基础的研究中，巴比里及其同事通过全外显子测序，在5.4%的原发性PCa中发现了一个新的反复突变基因MED12。MED12编码中介体复合物的一个亚基，是Wnt/β-连环蛋白信号的转导子，与刺猬信号通路的调节以及转化生长因子β（TGFβ）受体信号的调控相关。因此，这些研究促使我们去探究MED12在PCa中的相关性。通过对633例患者的组织芯片进行免疫组织化学分析，评估MED12的表达、SMAD3磷酸化及增殖标志物。在PCa细胞系中进行siRNA介导的MED12敲低，随后进行细胞增殖测定、细胞周期分析、凋亡测定以及用重组TGFβ3处理。我们发现，与雄激素敏感型PCa中低于11%的频率相比，远处转移去势抵抗性前列腺癌（CRPC（MET））的40%（28/70）和局部复发性CRPC（CRPC（LOC））的21%（19/90）中存在MED12核过表达，而在良性前列腺组织中无过表达。MED12表达与PCa组织中的高增殖活性显著相关，而MED12敲低则降低了增殖，减少了G1期到S期的转换，并增加了细胞周期抑制剂p27的表达。TGFβ信号激活与组织中MED12核过表达相关，并导致细胞系中MED12核表达强烈增加。此外，MED12敲低降低了TGFβ靶基因波形蛋白的表达。我们的研究结果表明，与雄激素敏感型PCa相比，MED12核过表达在CRPC中是常见事件，并且直接参与TGFβ信号传导。
