Cowell L N, Graham J D, Bouton A H, Clarke C L, O'Neill G M
Focal Adhesion Biology Group, The Oncology Research Unit, The Children's Hospital at Westmead, and Discipline of Paediatrics and Child Health, University of Sydney, Westmead, New South Wales, Australia.
Oncogene. 2006 Dec 7;25(58):7597-607. doi: 10.1038/sj.onc.1209747. Epub 2006 Jun 26.
Reports that the adhesion-associated molecule p130Cas/BCAR1 promotes resistance to tamoxifen suggested that adhesion-mediated signalling may be altered by tamoxifen treatment. We find that p130Cas/BCAR1 phosphorylation is enhanced in tamoxifen-treated estrogen receptor (ER)-positive MCF-7 breast cancer cells. The effects of estrogen and tamoxifen were assessed independently and in combination, and the results demonstrate that tamoxifen antagonizes estrogen regulation of p130Cas/BCAR1 phosphorylation. Phosphorylation correlates with tamoxifen ER antagonist effects, as phosphorylation effects are replicated by the pure antiestrogen ICI 182, 780. Correspondingly, phosphorylation is not changed in ER-negative cells exposed to tamoxifen. We show that deletion of the p130Cas/BCAR1 substrate domain substantially reduces tamoxifen-induced phosphorylation of p130Cas/BCAR1 and confers enhanced sensitivity to tamoxifen. P130Cas/BCAR1 forms a phosphorylation-dependent signalling complex with focal adhesion kinase (FAK) and Src kinase that promotes adhesion-mediated cell survival. Therefore, we examined the kinetics of p130Cas/BCAR1, Src and FAK phosphorylation over a 14-day time course and find sustained phosphorylation of these molecules after 7 days exposure to tamoxifen. Inhibition of Src kinase is shown to reduce tamoxifen-promoted p130Cas/BCAR1 phosphorylation and reduce cell viability. Stimulation of the Src/FAK/p130Cas/BCAR1 adhesion signalling pathway in tamoxifen-treated MCF-7 cells does not cause increased migration; however, there is Src-dependent phosphorylation of the cell survival molecule Akt. Correspondingly, Akt inhibition reduces cell viability in cells treated with tamoxifen. We propose that prolonged activation of adhesion-dependent signalling may confer a survival advantage in response to additional cellular insults or alternatively, may poise cells to develop a migratory phenotype in response to additional cellular cues.
有报道称，与黏附相关的分子p130Cas/BCAR1可促进对他莫昔芬的耐药性，这表明黏附介导的信号传导可能会因他莫昔芬治疗而改变。我们发现，在经他莫昔芬处理的雌激素受体（ER）阳性MCF-7乳腺癌细胞中，p130Cas/BCAR1的磷酸化增强。我们分别评估了雌激素和他莫昔芬的作用以及它们联合使用时的效果，结果表明他莫昔芬可拮抗雌激素对p130Cas/BCAR1磷酸化的调节作用。磷酸化与他莫昔芬的雌激素受体拮抗剂作用相关，因为纯抗雌激素药物ICI 182,780可重现磷酸化效应。相应地，在暴露于他莫昔芬的ER阴性细胞中，磷酸化水平没有变化。我们发现，缺失p130Cas/BCAR1底物结构域可显著降低他莫昔芬诱导的p130Cas/BCAR1磷酸化，并增强对他莫昔芬的敏感性。P130Cas/BCAR1与黏着斑激酶（FAK）和Src激酶形成磷酸化依赖性信号复合物，促进黏附介导的细胞存活。因此，我们在14天的时间进程中检测了p130Cas/BCAR1、Src和FAK磷酸化的动力学，发现暴露于他莫昔芬7天后，这些分子持续发生磷酸化。Src激酶的抑制作用可降低他莫昔芬促进的p130Cas/BCAR1磷酸化，并降低细胞活力。在经他莫昔芬处理的MCF-7细胞中刺激Src/FAK/p130Cas/BCAR1黏附信号通路不会导致细胞迁移增加；然而，细胞存活分子Akt存在Src依赖性磷酸化。相应地，Akt抑制可降低经他莫昔芬处理的细胞的活力。我们提出，黏附依赖性信号的长期激活可能会赋予细胞在应对其他细胞损伤时的生存优势，或者，可能使细胞在应对其他细胞信号时形成迁移表型。
