Breakthrough Breast Cancer Centre, Institute of Cancer Research, 237 Fulham Road, London SW3 6JJ, UK.
Breast Cancer Res. 2012 May 18;14(3):R78. doi: 10.1186/bcr3191.
The majority of breast tumors at primary diagnosis are estrogen receptor positive (ER+). Estrogen (E) mediates its effects by binding to the ER. Therapies targeting the estrogenic stimulation of tumor growth reduce mortality from ER+ breast cancer. However, resistance remains a major clinical problem.
To identify molecular mechanisms associated with resistance to E-deprivation, we assessed the temporal changes in global gene expression during adaptation to long-term culture of MCF7 human breast cancer cells in the absence of estradiol (E2), long term estrogen deprived (LTED), that leads to recovery of proliferative status and models resistance to an aromatase inhibitor (AI). The expression levels of proteins were determined by western blotting. Proliferation assays were carried out using the dual platelet derived growth factor receptor (PDGFR)/Abelson tyrosine kinase (Abl) inhibitor nilotinib. Luciferase reporter assays were used to determine effects on ER-mediated transactivation. Changes in recruitment of cofactors to the gene regulated by estrogen in breast cancer 1 (GREB1) promoter were determined by chromatin immunoprecipitation (ChIP). Gene expression data were derived from 81 postmenopausal women with ER+ BC pre-treatment and at two-weeks post-treatment with single agent anastrozole in a neoadjuvant trial.
The PDGF/Abl canonical pathway was significantly elevated as early as one week post E-deprivation (P = 1.94 E-04) and this became the top adaptive pathway at the point of proliferative recovery (P = 1.15 E-07). Both PDGFRβ and Abl protein levels were elevated in the LTED cells compared to wild type (wt)-MCF7 cells. The PDGF/Abl tyrosine kinase inhibitor nilotinib, suppressed proliferation in LTED cells in the presence or absence of E. Nilotinib also suppressed ER-mediated transcription by destabilizing the ER and reducing recruitment of amplified in breast cancer-1 (AIB1) and the CREB binding protein (CBP) to the promoter of the E-responsive gene GREB1. High PDGFRβ in primary ER+ breast cancer of 81 patients prior to neoadjuvant treatment with an AI was associated with poorer antiproliferative response. Additionally PDGFRβ expression increased after two weeks of AI therapy (1.25 fold, P = 0.003).
These preclinical and clinical data indicate that the PDGF/Abl signaling pathway merits clinical evaluation as a therapeutic target with endocrine therapy in ER+ breast cancer.
大多数原发性乳腺癌肿瘤雌激素受体阳性（ER+）。雌激素（E）通过与 ER 结合来发挥其作用。靶向雌激素刺激肿瘤生长的治疗方法降低了 ER+乳腺癌的死亡率。然而，耐药性仍然是一个主要的临床问题。
为了确定与 E 剥夺耐药相关的分子机制，我们评估了 MCF7 人乳腺癌细胞在缺乏雌二醇（E2）的情况下长期培养过程中（LTED），导致增殖状态恢复和对芳香酶抑制剂（AI）耐药模型的全球基因表达的时间变化。通过 Western 印迹测定蛋白质的表达水平。使用双重血小板衍生生长因子受体（PDGFR）/Abelson 酪氨酸激酶（Abl）抑制剂 nilotinib 进行增殖测定。使用荧光素酶报告基因测定确定对 ER 介导的转录激活的影响。通过染色质免疫沉淀（ChIP）确定调节乳腺癌 1（GREB1）启动子的基因的共因子募集变化。基因表达数据来自 81 名绝经后 ER+BC 患者，这些患者在新辅助试验中接受单药阿那曲唑治疗前和治疗后两周。
早在 E 剥夺后一周（P = 1.94E-04），PDGF/Abl 经典途径就显著升高，并且在增殖恢复时成为顶级适应途径（P = 1.15E-07）。与野生型（wt）-MCF7 细胞相比，LTED 细胞中的 PDGFRβ 和 Abl 蛋白水平升高。PDGF/Abl 酪氨酸激酶抑制剂 nilotinib 在存在或不存在 E 的情况下抑制 LTED 细胞的增殖。Nilotinib 通过使 ER 不稳定并减少扩增的乳腺癌-1（AIB1）和 CREB 结合蛋白（CBP）募集到 E 反应基因 GREB1 的启动子，也抑制了 ER 介导的转录。81 名接受 AI 新辅助治疗的原发性 ER+乳腺癌患者的 PDGFRβ 水平较高，与较差的抗增殖反应相关。此外，PDGFRβ 的表达在 AI 治疗两周后增加（1.25 倍，P = 0.003）。
这些临床前和临床数据表明，PDGF/Abl 信号通路值得在 ER+乳腺癌中与内分泌治疗一起进行临床评估，作为一种治疗靶标。
