Department of Prostate Cancer Research, University Hospital of Bonn, Bonn, Germany; Institute of Pathology, University Hospital of Bonn, Bonn, Germany.
Int J Cancer. 2014 Jul 1;135(1):19-26. doi: 10.1002/ijc.28647. Epub 2013 Dec 9.
The mediator complex is an evolutionary conserved key regulator of transcription of protein-coding genes and an integrative hub for diverse signaling pathways. In this study, we investigated whether the mediator subunit MED15 is implicated in castration-resistant prostate cancer (CRPC). MED15 expression and copy number/rearrangement status were assessed by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), respectively on 718 prostate cancer (PCa) specimens and sequenced by Sanger on a subset. Furthermore, SMAD3 phosphorylation, androgen receptor (AR) and proliferation markers were evaluated by IHC. In PCa cells, siRNA/shRNA knockdown of MED15 was followed by proliferation assays with/without dihydrotestosterone (DHT), and treatments with recombinant TGF-β3. Our results show that MED15 is overexpressed in 76% of distant metastatic CRPC (CRPC(MET) ) and 70% of local-recurrent CRPC (CRPC(LOC) ), in contrast to low frequencies in androgen-sensitive PCa, and no expression in benign prostatic tissue. Furthermore, MED15 overexpression correlates with worse clinical outcome thus defining a highly lethal phenotype. Moreover, TGF-β signaling activation associates with MED15 overexpression in PCa tissues, and leads to increased expression of MED15 in PCa cells. MED15 knockdown effects phosphorylation and shuttling of p-SMAD3 to the nucleus as well as TGF-β-enhanced proliferation. In PCa tissues, MED15 overexpression associates with AR overexpression/amplification and correlates with high proliferative activity. MED15 knockdown decreases both androgen-dependent and -independent proliferation in PCa cells. Taken together, these findings implicate MED15 in CRPC, and as MED15 is evolutionary conserved, it is likely to emerge as a lethal phenotype in other therapeutic-resistant diseases, and not restricted to our disease model.
中介复合物是调节蛋白编码基因转录的进化保守的关键调控因子，也是多种信号通路的整合中心。在这项研究中，我们研究了调节子亚基 MED15 是否与去势抵抗性前列腺癌（CRPC）有关。通过免疫组织化学（IHC）和荧光原位杂交（FISH）分别评估了 718 例前列腺癌（PCa）标本中的 MED15 表达和拷贝数/重排状态，并对亚组进行了 Sanger 测序。此外，通过免疫组织化学评估了 SMAD3 磷酸化、雄激素受体（AR）和增殖标志物。在 PCa 细胞中，用 siRNA/shRNA 敲低 MED15 后，进行了有/无二氢睾酮（DHT）和重组 TGF-β3 处理的增殖试验。我们的结果表明，在远处转移性 CRPC（CRPC(MET)）和局部复发性 CRPC（CRPC(LOC)）中，MED15 过表达率分别为 76%和 70%，而在雄激素敏感的 PCa 中过表达率较低，在良性前列腺组织中无表达。此外，MED15 过表达与更差的临床结局相关，从而定义了一个高致死表型。此外，TGF-β信号转导激活与 PCa 组织中的 MED15 过表达相关，并导致 PCa 细胞中 MED15 的表达增加。MED15 敲低影响 p-SMAD3 的磷酸化和易位到核内，以及 TGF-β增强的增殖。在 PCa 组织中，MED15 过表达与 AR 过表达/扩增相关，并与高增殖活性相关。MED15 敲低降低了 PCa 细胞中雄激素依赖性和非依赖性增殖。综上所述，这些发现表明 MED15 与 CRPC 有关，并且由于 MED15 在进化上是保守的，因此它可能在其他治疗耐药性疾病中出现致死表型，而不仅仅限于我们的疾病模型。
