Soady Kelly J, Kendrick Howard, Gao Qiong, Tutt Andrew, Zvelebil Marketa, Ordonez Liliana D, Quist Jelmar, Tan David Wei-Min, Isacke Clare M, Grigoriadis Anita, Smalley Matthew J
Breast Cancer Res. 2015 Mar 4;17(1):31. doi: 10.1186/s13058-015-0539-6.
Triple-negative breast cancer (TNBC) is a heterogeneous group of tumours in which chemotherapy, the current mainstay of systemic treatment, is often initially beneficial but with a high risk of relapse and metastasis. There is currently no means of predicting which TNBC will relapse. We tested the hypothesis that the biological properties of normal stem cells are re-activated in tumour metastasis and that, therefore, the activation of normal mammary stem cell-associated gene sets in primary TNBC would be highly prognostic for relapse and metastasis.
Mammary basal stem and myoepithelial cells were isolated by flow cytometry and tested in low-dose transplant assays. Gene expression microarrays were used to establish expression profiles of the stem and myoepithelial populations; these were compared to each other and to our previously established mammary epithelial gene expression profiles. Stem cell genes were classified by Gene Ontology (GO) analysis and the expression of a subset analysed in the stem cell population at single cell resolution. Activation of stem cell genes was interrogated across different breast cancer cohorts and within specific subtypes and tested for clinical prognostic power.
A set of 323 genes was identified that was expressed significantly more highly in the purified basal stem cells compared to all other cells of the mammary epithelium. A total of 109 out of 323 genes had been associated with stem cell features in at least one other study in addition to our own, providing further support for their involvement in the biology of this cell type. GO analysis demonstrated an enrichment of these genes for an association with cell migration, cytoskeletal regulation and tissue morphogenesis, consistent with a role in invasion and metastasis. Single cell resolution analysis showed that individual cells co-expressed both epithelial- and mesenchymal-associated genes/proteins. Most strikingly, we demonstrated that strong activity of this stem cell gene set in TNBCs identified those tumours most likely to rapidly progress to metastasis.
Our findings support the hypothesis that the biological properties of normal stem cells are drivers of metastasis and that these properties can be used to stratify patients with a highly heterogeneous disease such as TNBC.
三阴性乳腺癌（TNBC）是一组异质性肿瘤，化疗作为目前全身治疗的主要手段，通常在初始阶段有益，但复发和转移风险很高。目前尚无预测哪些TNBC会复发的方法。我们检验了这样一个假设，即正常干细胞的生物学特性在肿瘤转移中被重新激活，因此，原发性TNBC中正常乳腺干细胞相关基因集的激活对复发和转移具有高度的预后价值。
通过流式细胞术分离乳腺基底干细胞和肌上皮细胞，并在低剂量移植试验中进行检测。利用基因表达微阵列建立干细胞和肌上皮群体的表达谱；将这些表达谱相互比较，并与我们之前建立的乳腺上皮基因表达谱进行比较。通过基因本体论（GO）分析对干细胞基因进行分类，并在单细胞分辨率下分析干细胞群体中一个子集的表达。在不同的乳腺癌队列以及特定亚型中研究干细胞基因的激活情况，并测试其临床预后能力。
鉴定出一组323个基因，与乳腺上皮的所有其他细胞相比，这些基因在纯化的基底干细胞中表达明显更高。在323个基因中，共有109个基因在除我们自己的研究之外的至少一项其他研究中与干细胞特征相关，这为它们参与这种细胞类型的生物学过程提供了进一步支持。GO分析表明，这些基因在与细胞迁移、细胞骨架调节和组织形态发生的关联方面富集，这与它们在侵袭和转移中的作用一致。单细胞分辨率分析表明，单个细胞同时共表达上皮和间充质相关的基因/蛋白质。最引人注目的是，我们证明了TNBC中这个干细胞基因集的强活性可识别出那些最有可能迅速进展为转移的肿瘤。
我们的研究结果支持这样一个假设，即正常干细胞的生物学特性是转移的驱动因素，并且这些特性可用于对TNBC这种高度异质性疾病的患者进行分层。
