Center for Molecular Systems Biology, University of Turin, Turin, Italy.
Oncogene. 2012 Oct 4;31(40):4353-61. doi: 10.1038/onc.2011.627. Epub 2012 Jan 16.
Pharmacological resistance is a serious threat to the clinical success of hormone therapy for breast cancer. The antiproliferative response to antagonistic drugs such as tamoxifen (Tam) critically depends on the recruitment of NCoR/SMRT corepressors to estrogen receptor alpha (ERα) bound to estrogen target genes. Under certain circumstances, as demonstrated in the case of interleukin-1β (IL-1β) treatment, the protein Tab2 interacts with ERα/NCoR and causes dismissal of NCoR from these genes, leading to loss of the antiproliferative response. In Tam-resistant (TamR) ER-positive breast cancer cells, we observed that Tab2 presents a shift in mobility on sodium dodecyl sulfate--PAGE (SDS-PAGE) similar to that seen in MCF7 wt upon stimulation with IL-1β, suggesting constitutive activation. Accordingly, TamR treatment with Tab2-specific short interfering RNA, restored the antiproliferative response to Tam in these cells. As Tab2 is known to directly interact with the N-terminal domain of ERα, we synthesized a peptide composed of a 14-aa motif of this domain, which effectively competes with ERα/Tab2 interaction in pull-down and co-immunoprecipitation experiments, fused to the carrier TAT peptide to allow internalization. Treatment of TamR cells with this peptide resulted in partial recovery of the antiproliferative response to Tam, suggesting a strategy to revert pharmacological resistance in breast cancer. Silencing of Tab2 in TamR cells by siRNA caused modulation of a gene set related to the control of cell cycle and extensively connected to BRCA1 in a functional network. These genes were able to discern two groups of patients, from a published data set of Tam-treated breast cancer profiles, with significantly different disease-free survival. Altogether, our data implicate Tab2 as a mediator of resistance to endocrine therapy and as a potential new target to reverse pharmacological resistance and potentiate antiestrogen action.
药物抵抗是激素疗法治疗乳腺癌临床成功的严重威胁。拮抗药物（如他莫昔芬[Tam]）的抗增殖反应取决于核受体共抑制因子/沉默调节因子（NCoR/SMRT）核心抑制物募集到与雌激素靶基因结合的雌激素受体α（ERα）。在某些情况下，如白细胞介素-1β（IL-1β）治疗的情况所示，蛋白质 Tab2 与 ERα/NCoR 相互作用，并导致 NCoR 从这些基因中被解雇，从而导致抗增殖反应的丧失。在 Tam 耐药（TamR）ER 阳性乳腺癌细胞中，我们观察到 Tab2 在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE）上的迁移与 MCF7wt 在受到 IL-1β刺激时相似，表明其持续激活。因此，用 Tab2 特异性短发夹 RNA（siRNA）处理 TamR 可恢复这些细胞对 Tam 的抗增殖反应。由于 Tab2 已知与 ERα 的 N 端结构域直接相互作用，我们合成了一个由该结构域的 14 个氨基酸基序组成的肽，该肽在下拉和共免疫沉淀实验中有效地与 ERα/Tab2 相互作用竞争，融合到载体 TAT 肽中以允许内化。用该肽处理 TamR 细胞导致对 Tam 的抗增殖反应部分恢复，提示了一种逆转乳腺癌药物抵抗的策略。用 siRNA 沉默 TamR 细胞中的 Tab2 导致与细胞周期控制相关的基因集的调制，并在功能网络中与 BRCA1 广泛连接。这些基因能够从 Tam 治疗的乳腺癌图谱的已发表数据集区分出两组患者，他们的无病生存率有显著差异。总的来说，我们的数据表明 Tab2 是内分泌治疗耐药的介质，也是逆转药物耐药和增强抗雌激素作用的潜在新靶点。
