Hiscox Stephen, Jiang Wen Go, Obermeier Kathrin, Taylor Kathryn, Morgan Liam, Burmi Raj, Barrow Denise, Nicholson Robert I
Tenovus Centre for Cancer Research, Welsh School of Pharmacy, Cardiff University, Cardiff, United Kingdom.
Int J Cancer. 2006 Jan 15;118(2):290-301. doi: 10.1002/ijc.21355.
We have previously demonstrated that, following acquisition of endocrine resistance, breast cancer cells display an altered growth rate together with increased aggressive behaviour in vitro. Since dysfunctional cell-cell adhesive interactions can promote an aggressive phenotype, we investigated the integrity of this protein complex in our breast cancer model of tamoxifen resistance. In culture, tamoxifen-resistant MCF7 (TamR) cells grew as loosely packed colonies with loss of cell-cell junctions and demonstrated altered morphology characteristic of cells undergoing epithelial-to-mesenchymal transition (EMT). Neutralising E-cadherin function promoted the invasion and inhibited the aggregation of endocrine-sensitive MCF7 cells, whilst having little effect on the behaviour of TamR cells. Additionally, TamR cells had increased levels of tyrosine-phosphorylated beta-catenin, whilst serine/threonine-phosphorylated beta-catenin was decreased. These cells also displayed loss of association between beta-catenin and E-cadherin, increased cytoplasmic and nuclear beta-catenin and elevated transcription of beta-catenin target genes known to be involved in tumour progression and EMT. Inhibition of EGFR kinase activity in TamR cells reduced beta-catenin tyrosine phosphorylation, increased beta-catenin-E-cadherin association and promoted cell-cell adhesion. In such treated cells, the association of beta-catenin with Lef-1 and the transcription of c-myc, cyclin-D1, CD44 and COX-2 were also reduced. These results suggest that homotypic adhesion in tamoxifen-resistant breast cancer cells is dysfunctional due to EGFR-driven modulation of the phosphorylation status of beta-catenin and may contribute to an enhanced aggressive phenotype and transition towards a mesenchymal phenotype in vitro.
我们之前已经证明，在获得内分泌耐药性后，乳腺癌细胞在体外表现出生长速率改变以及侵袭性增强。由于功能失调的细胞间黏附相互作用可促进侵袭性表型，我们在他莫昔芬耐药的乳腺癌模型中研究了这种蛋白复合物的完整性。在培养过程中，他莫昔芬耐药的MCF7（TamR）细胞以松散堆积的集落形式生长，细胞间连接丧失，并表现出经历上皮-间质转化（EMT）的细胞特征性的形态改变。中和E-钙黏蛋白功能可促进内分泌敏感的MCF7细胞的侵袭并抑制其聚集，而对TamR细胞的行为影响很小。此外，TamR细胞中酪氨酸磷酸化的β-连环蛋白水平升高，而丝氨酸/苏氨酸磷酸化的β-连环蛋白水平降低。这些细胞还表现出β-连环蛋白与E-钙黏蛋白之间的结合丧失、细胞质和细胞核中β-连环蛋白增加以及已知参与肿瘤进展和EMT的β-连环蛋白靶基因的转录升高。抑制TamR细胞中的EGFR激酶活性可降低β-连环蛋白酪氨酸磷酸化、增加β-连环蛋白-E-钙黏蛋白结合并促进细胞间黏附。在这种处理过的细胞中，β-连环蛋白与Lef-1的结合以及c-myc、细胞周期蛋白D1、CD44和COX-2的转录也降低。这些结果表明，他莫昔芬耐药的乳腺癌细胞中的同型黏附功能失调是由于EGFR驱动的β-连环蛋白磷酸化状态调节所致，并且可能有助于增强侵袭性表型以及在体外向间质表型转变。
