Triple negative breast cancer (TNBC) is a highly heterogeneous disease, which influences the therapeutic response and makes difficult the discovery of effective targets. This heterogeneity is attributed to the presence of breast cancer stem cells (BCSCs), which determines resistance to chemotherapy and subsequently disease recurrence and metastasis. In this context, this work aimed to evaluate the morphological and phenotypic cellular heterogeneity of two TNBC cell lines cultured in monolayer and tumorsphere (TS) models by fluorescence and electron microscopy and flow cytometry. The BT-549 and Hs 578T analyses demonstrated large phenotypic and morphological heterogeneity between these cell lines, as well as between the cell subpopulations that compose them. BT-549 and Hs 578T are heterogeneous considering the cell surface marker CD44 and CD24 expression, characterizing BCSC mesenchymal-like cells (CD44+/CD24-), epithelial cells (CD44-/CD24+), hybrid cells with mesenchymal and epithelial features (CD44+/CD24+), and CD44-/CD24- cells. BCSC epithelial-like cells (ALDH+) were found in BT-549, BT-549 TS, and Hs 578T TS; however, only BT-549 TS showed a high ALDH activity. Ultrastructural characterization showed the heterogeneity within and among BT-549 and Hs 578T in monolayer and TS models being formed by more than one cellular type. Further, the mesenchymal characteristic of these cells is demonstrated by E-cadherin absence and filopodia. It is well known that tumor cell heterogeneity can influence survival, therapy responses, and the rate of tumor growth. Thus, molecular understanding of this heterogeneity is essential for the identification of potential therapeutic options and vulnerabilities of oncological patients.

中文翻译：

---

三阴性乳腺癌细胞系和乳腺癌干细胞亚群的表型，结构和超微结构分析。

三阴性乳腺癌（TNBC）是一种高度异质性疾病，会影响治疗反应并难以发现有效靶标。这种异质性归因于乳腺癌干细胞（BCSC）的存在，它决定了对化学疗法的抵抗力，进而决定了疾病的复发和转移。在这种情况下，这项工作旨在通过荧光，电子显微镜和流式细胞术评估在单层和肿瘤球（TS）模型中培养的两种TNBC细胞系的形态和表型细胞异质性。BT-549和Hs 578T分析表明，这些细胞系之间以及组成它们的细胞亚群之间存在较大的表型和形态异质性。考虑到细胞表面标记CD44和CD24的表达，BT-549和Hs 578T是异质的，表征BCSC间充质样细胞（CD44 + / CD24-），上皮细胞（CD44- / CD24 +），具有间充质和上皮特征的杂交细胞（CD44 + / CD24 +）和CD44- / CD24-细胞。在BT-549，BT-549 TS和Hs 578T TS中发现了BCSC上皮样细胞（ALDH +）。然而，只有BT-549 TS显示出高的ALDH活性。超微结构表征显示在单层和TS模型中BT-549和Hs 578T内部和之间的异质性是由一种以上的细胞类型形成的。此外，这些细胞的间充质特征通过E-钙粘着蛋白的缺失和丝状伪足得以证明。众所周知，肿瘤细胞的异质性会影响存活率，治疗反应以及肿瘤的生长速度。从而，