Tevis Kristie M, Cecchi Ryan J, Colson Yolonda L, Grinstaff Mark W
Department of Biomedical Engineering, Cummington Street, Boston University, Boston, MA 02215, United States.
Division of Thoracic Surgery, Department of Surgery, Brigham and Women's Hospital, Boston, MA 02215, United States.
Acta Biomater. 2017 Mar 1;50:271-279. doi: 10.1016/j.actbio.2016.12.037. Epub 2016 Dec 21.
Tumor associated macrophages (TAMs) are critical stromal components intimately involved with the progression, invasion, and metastasis of cancer cells. To address the need for an in vitro system that mimics the clinical observations of TAM localizations and subsequent functional performance, a cancer cell/macrophage spheroid model is described. The central component of the model is a triple negative breast cancer spheroid embedded in a three-dimensional collagen gel. Macrophages are incorporated in two different ways. The first is a heterospheroid, a spheroid containing both tumor cells and macrophages. The heterospheroid mimics the population of TAMs infiltrated into the tumor mass, thus being exposed to hypoxia and metabolic gradients. In the second model, macrophages are diffusely seeded in the collagen surrounding the spheroid, thus modeling TAMs in the cancer stroma. The inclusion of macrophages as a heterospheroid changes the metabolic profile, indicative of synergistic growth. In contrast, macrophages diffusely seeded in the collagen bear the same profile regardless of the presence of a tumor cell spheroid. The macrophages in the heterospheroid secrete EGF, a cytokine critical to tumor/macrophage co-migration, and an EGF inhibitor decreases the metabolic activity of the heterospheroid, which is not observed in the other systems. The increased secretion of IL-10 indicates that the heterospheroid macrophages follow an M2/TAM differentiation pathway. Lastly, the heterospheroid exhibits resistance to paclitaxel. In summary, the collagen embedded heterospheroid model promotes TAM-like characteristics, and will be of utility in cancer biology and drug discovery.
Two in vitro collagen-embedded multicellular spheroid models are described that mimic the clinical observations of macrophage localization within a tumor. Incorporation of macrophages within a breast cancer spheroid emphasizes cell-cell interactions with subsequent differentiation toward a tumor-promoting TAM phenotype. In contrast, macrophages seeded around the tumor spheroid display decreased interaction with cancer cells and no indication of a TAM phenotype. Finally, the presence of macrophages in the heterospheroid increases resistance to paclitaxel. This study demonstrates that cell-cell interactions and 3D collagen matrix direct macrophage activity, and, thus, highlights the important role the local environment itself plays in macrophage behavior.
肿瘤相关巨噬细胞（TAM）是关键的基质成分，与癌细胞的进展、侵袭和转移密切相关。为满足对一种体外系统的需求，该系统可模拟TAM定位及后续功能表现的临床观察结果，本文描述了一种癌细胞/巨噬细胞球体模型。该模型的核心成分是嵌入三维胶原凝胶中的三阴性乳腺癌球体。巨噬细胞以两种不同方式纳入。第一种是异质球体，即包含肿瘤细胞和巨噬细胞的球体。异质球体模拟浸润到肿瘤块中的TAM群体，因此暴露于缺氧和代谢梯度中。在第二种模型中，巨噬细胞分散接种在球体周围的胶原中，从而模拟癌基质中的TAM。作为异质球体包含巨噬细胞会改变代谢谱，表明存在协同生长。相比之下，无论肿瘤细胞球体是否存在，分散接种在胶原中的巨噬细胞具有相同的代谢谱。异质球体中的巨噬细胞分泌表皮生长因子（EGF），这是一种对肿瘤/巨噬细胞共同迁移至关重要的细胞因子，而EGF抑制剂会降低异质球体的代谢活性，这在其他系统中未观察到。白细胞介素-10分泌增加表明异质球体巨噬细胞遵循M2/TAM分化途径。最后，异质球体对紫杉醇具有抗性。总之，胶原包埋的异质球体模型促进了TAM样特征，将在癌症生物学和药物发现中发挥作用。
本文描述了两种体外胶原包埋的多细胞球体模型，它们模拟了巨噬细胞在肿瘤内定位的临床观察结果。将巨噬细胞纳入乳腺癌球体中强调了细胞间相互作用以及随后向促进肿瘤的TAM表型分化。相比之下，接种在肿瘤球体周围的巨噬细胞与癌细胞的相互作用减少，且没有TAM表型的迹象。最后，异质球体中巨噬细胞的存在增加了对紫杉醇的抗性。本研究表明细胞间相互作用和三维胶原基质指导巨噬细胞活性，因此突出了局部环境本身在巨噬细胞行为中所起的重要作用。
