Institute of Oncology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.
Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Clin Cancer Res. 2019 May 1;25(9):2900-2914. doi: 10.1158/1078-0432.CCR-18-1505. Epub 2019 Feb 7.
Mutations in the ligand-binding domain (LBD) of estrogen receptor α (ER) confer constitutive transcriptional activity and resistance to endocrine therapies in patients with breast cancer. Accumulating clinical data suggest adverse outcome for patients harboring tumors expressing these mutations. We aimed to elucidate mechanisms conferring this aggressive phenotype.
Cells constitutively expressing physiologic levels of ER-harboring activating LBD mutations were generated and characterized for viability, invasiveness, and tumor formation . Gene expression profile was studied using microarray and RNAseq technologies. Metabolic properties of the cells were assessed using global metabolite screen and direct measurement of metabolic activity.
Cells expressing mutated ER showed increased proliferation, migration, and tumorigenicity compared with cells expressing the wild-type ER (WT-ER), even in the presence of estrogen. Expression of the mutated ER was associated with upregulation of genes involved in invasion and metastases, as well as elevation of genes associated with tumor cell metabolism. Indeed, a metabolic examination revealed four distinct metabolic profiles: WT-ER-expressing cells either untreated or estrogen treated and mutated ER-expressing cells either untreated or estrogen treated. Pathway analyses indicated elevated tricarboxylic acid cycle activity of 537S-ER-expressing cells. Thus, while WT-ER cells were mostly glucose-dependent, 537S-ER were not addicted to glucose and were able to utilize glutamine as an alternative carbon source.
Taken together, these data indicate estrogen-independent rewiring of breast cancer cell metabolism by LBD-activating mutations. These unique metabolic activities may serve as a potential vulnerability and aid in the development of novel treatment strategies to overcome endocrine resistance.
雌激素受体 α（ER）配体结合域（LBD）中的突变赋予乳腺癌患者的肿瘤细胞组成型转录活性和对内分泌治疗的耐药性。越来越多的临床数据表明，携带这些突变的肿瘤患者预后不良。我们旨在阐明赋予这种侵袭性表型的机制。
构建并鉴定了持续表达生理水平的携带 ER 激活 LBD 突变的细胞，以评估其活力、侵袭性和肿瘤形成能力。利用微阵列和 RNAseq 技术研究基因表达谱。通过全局代谢物筛选和代谢活性的直接测量来评估细胞的代谢特性。
与表达野生型 ER（WT-ER）的细胞相比，表达突变型 ER 的细胞增殖、迁移和肿瘤形成能力增强，即使存在雌激素也是如此。突变型 ER 的表达与侵袭和转移相关基因的上调以及与肿瘤细胞代谢相关基因的上调有关。实际上，代谢检查显示存在四种不同的代谢谱：未处理或用雌激素处理的 WT-ER 表达细胞，以及未处理或用雌激素处理的突变型 ER 表达细胞。通路分析表明，537S-ER 表达细胞的三羧酸循环活性升高。因此，虽然 WT-ER 细胞主要依赖葡萄糖，但 537S-ER 不依赖于葡萄糖，并且能够利用谷氨酰胺作为替代碳源。
这些数据表明，LBD 激活突变导致雌激素非依赖性的乳腺癌细胞代谢重编程。这些独特的代谢活性可能成为潜在的弱点，并有助于开发新的治疗策略来克服内分泌耐药性。
