Deciphering the gene expression network regulated by ETV7

Cancer stem cells (CSCs) represent a population of cells within the tumor able to drive tumorigenesis and known to be highly resistant to conventional chemotherapy and radiotherapy. In this work, we show a new role for ETV7, a transcriptional repressor member of the ETS family, in promoting breast cancer stem-like cells plasticity and resistance to chemo- and radiotherapy in breast cancer (BC) cells. We observed that MCF7 and T47D BC-derived cells stably over-expressing ETV7 showed reduced sensitivity to the chemotherapeutic drug 5-Flouororuacil and to radiotherapy, accompanied by an adaptive proliferative behavior observed in different culture conditions. We further noticed that alteration of ETV7 expression could significantly affect the population of breast CSCs, measured by CD44+/CD24low cell population and mammosphere formation efficiency. By transcriptome profiling, we identified a signature of Interferon-responsive genes significantly repressed in cells over-expressing ETV7, which could be responsible for the increase in the breast CSCs population, as this could be partially reverted by the treatment with IFN-b. Lastly, we show that the expression of the IFN-responsive genes repressed by ETV7 could have prognostic value in breast cancer, as low expression of these genes was associated with a worse prognosis. Therefore, we propose a novel role for ETV7 in breast cancer stem cells’ plasticity and associated resistance to conventional chemotherapy and radiotherapy, which involves the repression of a group of IFN-responsive genes, potentially reversible upon IFN-b treatment. We, therefore, suggest that an in-depth investigation of this mechanism could lead to novel breast CSCs targeted therapies and to the improvement of combinatorial regimens, possibly involving the therapeutic use of IFN-b, with the aim of avoiding resistance development and relapse in breast cancer. We analyzed gene expression from 2 breast cancer-derived cell lines (MCF7 and T47D) stably transfected with ETV7 or an empty vector (pAIP backbone) as a control. Three biological replicates for each condition (4 Samples) have been prepared and processed.

肿瘤干细胞（Cancer stem cells, CSCs）是肿瘤内能够驱动肿瘤发生、且已知对常规化疗与放疗具有高度抗性的细胞群体。本研究揭示了ETS家族转录抑制因子ETV7在乳腺癌细胞中促进乳腺癌干细胞样细胞可塑性以及增强化疗与放疗抗性的新功能。
我们观察到，稳定过表达ETV7的MCF7与T47D乳腺癌来源细胞，对化疗药物5-氟尿嘧啶及放疗的敏感性均降低，且在多种培养条件下呈现出适应性增殖表型。
我们进一步发现，ETV7表达的改变可显著影响乳腺癌干细胞群体的比例，该效应可通过CD44+/CD24low细胞群占比与乳腺球形成效率进行评估。
通过转录组谱分析，我们鉴定出一类在ETV7过表达细胞中显著被抑制的干扰素应答基因特征，这类基因可能与乳腺癌干细胞群体的扩增有关——用干扰素β（IFN-β）处理可部分逆转这一效应。
此外，我们发现ETV7所抑制的干扰素应答基因的表达水平对乳腺癌具有预后价值：这些基因的低表达与较差的预后相关。
因此，我们提出ETV7通过抑制一类干扰素应答基因（该效应可被IFN-β处理部分逆转），在乳腺癌干细胞可塑性以及伴随的常规化疗与放疗抗性中发挥全新的调控作用。据此，我们建议对这一机制展开深入研究，有望开发新型乳腺癌干细胞靶向疗法，并优化可能包含IFN-β治疗在内的联合用药方案，以期规避乳腺癌的耐药性产生与复发。
本研究分析了2株乳腺癌来源细胞系（MCF7与T47D）的基因表达情况，这些细胞被稳定转染了ETV7表达质粒或作为对照的空载体（pAIP骨架）。每个条件设置3个生物学重复，共计4份样本完成制备与测序分析。