Division of Translational Cancer Research, Department of Laboratory Medicine, Lund University Cancer Centre, Lund University, Lund, Sweden.
Department of Cellular and Molecular Medicine, University of Copenhagen, Copenhagen, Denmark.
Breast Cancer Res. 2024 Jan 16;26(1):11. doi: 10.1186/s13058-024-01763-3.
Human breast cancer most frequently originates within a well-defined anatomical structure referred to as the terminal duct lobular unit (TDLU). This structure is endowed with its very own lobular fibroblasts representing one out of two steady-state fibroblast subtypes-the other being interlobular fibroblasts. While cancer-associated fibroblasts (CAFs) are increasingly appreciated as covering a spectrum of perturbed states, we lack a coherent understanding of their relationship-if any-with the steady-state fibroblast subtypes. To address this, we here established two autologous CAF lines representing inflammatory CAFs (iCAFs) and myofibroblast CAFs (myCAFs) and compared them with already established interlobular- and lobular fibroblasts with respect to their origin and impact on tumor formation.
Primary breast tumor-derived CAFs were transduced to express human telomerase reverse transcriptase (hTERT) and sorted into CD105 and CD105 populations using fluorescence-activated cell sorting (FACS). The two populations were tested for differentiation similarities to iCAF and myCAF states through transcriptome-wide RNA-Sequencing (RNA-Seq) including comparison to an available iCAF-myCAF cell state atlas. Inference of origin in interlobular and lobular fibroblasts relied on RNA-Seq profiles, immunocytochemistry and growth characteristics. Osteogenic differentiation and bone formation assays in culture and in vivo were employed to gauge for origin in bone marrow-derived mesenchymal stem cells (bMSCs). Functional characteristics were assessed with respect to contractility in culture and interaction with tumor cells in mouse xenografts. The cells' gene expression signatures were tested for association with clinical outcome of breast cancer patients using survival data from The Cancer Genome Atlas database.
We demonstrate that iCAFs have properties in common with interlobular fibroblasts while myCAFs and lobular fibroblasts are related. None of the CAFs qualify as bMSCs as revealed by lack of critical performance in bone formation assays. Functionally, myCAFs and lobular fibroblasts are almost equally tumor promoting as opposed to iCAFs and interlobular fibroblasts. A myCAF gene signature is found to associate with poor breast cancer-specific survival.
We propose that iCAFs and myCAFs originate in interlobular and lobular fibroblasts, respectively, and more importantly, that the tumor-promoting properties of lobular fibroblasts render the TDLU an epicenter for breast cancer evolution.
人类乳腺癌最常起源于一个明确的解剖结构，称为终末导管小叶单位（TDLU）。这个结构具有自己的小叶成纤维细胞，代表两种稳定状态成纤维细胞亚型之一——另一种是小叶间成纤维细胞。虽然癌症相关成纤维细胞（CAFs）作为覆盖一系列紊乱状态的特征越来越受到关注，但我们缺乏对其与稳定状态成纤维细胞亚型之间关系的一致理解。为了解决这个问题，我们在这里建立了两个自体 CAF 系，代表炎症性 CAFs（iCAFs）和肌成纤维细胞 CAFs（myCAFs），并将其与已经建立的小叶间和小叶成纤维细胞进行比较，比较它们的起源和对肿瘤形成的影响。
原代乳腺癌衍生的 CAFs 被转导表达人端粒酶逆转录酶（hTERT），并用荧光激活细胞分选（FACS）分选到 CD105 和 CD105 群体中。通过全转录组 RNA 测序（RNA-Seq）比较两种群体与现有 iCAF-myCAF 细胞状态图谱的分化相似性，包括差异表达分析。通过 RNA-Seq 谱、免疫细胞化学和生长特征推断小叶间和小叶成纤维细胞的起源。在培养和体内进行成骨分化和骨形成测定，以评估骨髓间充质干细胞（bMSCs）的起源。通过在小鼠异种移植中观察细胞的收缩性和与肿瘤细胞的相互作用来评估功能特征。使用来自癌症基因组图谱数据库的生存数据测试细胞的基因表达特征与乳腺癌患者临床结局的相关性。
我们证明 iCAFs 具有与小叶间成纤维细胞共同的特性，而 myCAFs 和小叶成纤维细胞是相关的。在骨形成测定中缺乏关键性能表明，没有一种 CAFs 可以归类为 bMSCs。在功能上，myCAFs 和小叶成纤维细胞与 iCAFs 和小叶间成纤维细胞一样具有促进肿瘤的作用。发现一个 myCAF 基因特征与乳腺癌特异性生存不良相关。
我们提出 iCAFs 和 myCAFs 分别起源于小叶间和小叶成纤维细胞，更重要的是，小叶成纤维细胞的促肿瘤特性使 TDLU 成为乳腺癌进化的核心。
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