Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, I-70125 Bari, Italy.
Clinical Experimental Oncology Laboratory, National Cancer Research Centre 'Giovanni Paolo II', I-70124 Bari, Italy.
Int J Oncol. 2015 Mar;46(3):1214-24. doi: 10.3892/ijo.2014.2805. Epub 2014 Dec 19.
Triple negative breast cancer (TNBC) patients cannot be treated with endocrine therapy or targeted therapies due to lack of related receptors. These patients overexpress the epidermal growth factor receptor (EGFR), but are resistant to tyrosine kinase inhibitors (TKIs) and anti-EGFR therapies. Mechanisms suggested for resistance to TKIs include EGFR independence, mutations and alterations in EGFR and in its downstream signalling pathways. Ligand-induced endocytosis and degradation of EGFR play important roles in the downregulation of the EGFR signal suggesting that its activity could be regulated by targeting its trafficking. Evidence in normal cells showing that the scaffolding protein Na+/H+ exchanger regulatory factor 1 (NHERF1) can associate with EGFR to regulate its trafficking, led us to hypothesize that NHERF1 expression levels could regulate EGFR trafficking and functional expression in TNBC cells and, in this way, modulate its role in progression and response to treatment. We investigated the subcellular localization of NHERF1 and its interaction with EGFR in a metastatic basal like TNBC cell model, MDA-MB‑231, and the role of forced NHERF1 overexpression and/or stimulation with EGF on the sensitivity to EGFR specific TKI treatment with gefitinib. Stimulation with EGF induces an interaction of NHERF1 with EGFR to regulate its localization, degradation and function. NHERF1 overexpression is sufficient to drive its interaction with EGFR in non-stimulated conditions, inhibits EGFR degradation and increases its retention time in the plasma membrane. Importantly, NHERF1 overexpression strongly sensitized the cell to the pharmacological inhibition by gefitinib of EGFR-driven growth, motility and invadopodia-dependent ECM proteolysis. The further determination of how the NHERF1‑EGFR interaction is regulated may improve our understanding of TNBC resistance to the action of existing anticancer drugs.
三阴性乳腺癌（TNBC）患者由于缺乏相关受体，无法接受内分泌治疗或靶向治疗。这些患者表皮生长因子受体（EGFR）过度表达，但对酪氨酸激酶抑制剂（TKIs）和抗 EGFR 治疗具有抗性。对 TKIs 耐药的机制包括 EGFR 独立性、EGFR 及其下游信号通路的突变和改变。EGFR 的配体诱导内吞和降解在 EGFR 信号下调中起重要作用，表明其活性可以通过靶向其运输来调节。在正常细胞中的证据表明，支架蛋白 Na+/H+交换调节因子 1（NHERF1）可以与 EGFR 结合，调节其运输，这使我们假设 NHERF1 表达水平可以调节 TNBC 细胞中 EGFR 的运输和功能表达，并以这种方式调节其在进展和对治疗反应中的作用。我们研究了转移性基底样 TNBC 细胞模型 MDA-MB-231 中 NHERF1 的亚细胞定位及其与 EGFR 的相互作用，以及强制过表达 NHERF1 和/或用 EGF 刺激对 EGFR 特异性 TKI 吉非替尼治疗敏感性的作用。EGF 的刺激诱导 NHERF1 与 EGFR 的相互作用，以调节其定位、降解和功能。NHERF1 的过表达足以在非刺激条件下驱动其与 EGFR 的相互作用，抑制 EGFR 的降解并增加其在质膜中的保留时间。重要的是，NHERF1 的过表达强烈使细胞对吉非替尼对 EGFR 驱动的生长、运动和依赖侵袭小泡的细胞外基质蛋白水解的药理学抑制作用敏感。进一步确定 NHERF1-EGFR 相互作用是如何调节的，可能会提高我们对 TNBC 对现有抗癌药物作用的耐药性的理解。
