Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Center for Integrative Chemical Biology and Drug Discovery, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Cancer Res. 2015 Apr 1;75(7):1244-54. doi: 10.1158/0008-5472.CAN-14-1616. Epub 2015 Jan 29.
Endothelial-to-mesenchymal transition (EndMT) occurs during development and underlies the pathophysiology of multiple diseases. In tumors, unscheduled EndMT generates cancer-associated myofibroblasts that fuel inflammation and fibrosis, and may contribute to vascular dysfunction that promotes tumor progression. We report that freshly isolated subpopulations of tumor-specific endothelial cells (TEC) from a spontaneous mammary tumor model undergo distinct forms of EndMT in response to TGFβ stimulation. Although some TECs strikingly upregulate α smooth muscle actin (SMA), a principal marker of EndMT and activated myofibroblasts, counterpart normal mammary gland endothelial cells (NEC) showed little change in SMA expression after TGFβ treatment. Compared with NECs, SMA(+) TECs were 40% less motile in wound-healing assays and formed more stable vascular-like networks in vitro when challenged with TGFβ. Lineage tracing using ZsGreen(Cdh5-Cre) reporter mice confirmed that only a fraction of vessels in breast tumors contain SMA(+) TECs, suggesting that not all endothelial cells (EC) respond identically to TGFβ in vivo. Indeed, examination of 84 TGFβ-regulated target genes revealed entirely different genetic signatures in TGFβ-stimulated NEC and TEC cultures. Finally, we found that basic FGF (bFGF) exerts potent inhibitory effects on many TGFβ-regulated genes but operates in tandem with TGFβ to upregulate others. ECs challenged with TGFβ secrete bFGF, which blocks SMA expression in secondary cultures, suggesting a cell-autonomous or lateral-inhibitory mechanism for impeding mesenchymal differentiation. Together, our results suggest that TGFβ-driven EndMT produces a spectrum of EC phenotypes with different functions that could underlie the plasticity and heterogeneity of the tumor vasculature.
内皮-间充质转化（EndMT）发生在发育过程中，并为多种疾病的病理生理学提供基础。在肿瘤中，非计划性的 EndMT 产生了与癌症相关的肌成纤维细胞，这些细胞促进炎症和纤维化，并可能导致促进肿瘤进展的血管功能障碍。我们报告称，从自发乳腺肿瘤模型中分离的肿瘤特异性内皮细胞（TEC）亚群在受到 TGFβ刺激时会经历不同形式的 EndMT。虽然一些 TEC 明显上调了α平滑肌肌动蛋白（αSMA），这是 EndMT 和激活的肌成纤维细胞的主要标志物，但相应的正常乳腺内皮细胞（NEC）在 TGFβ处理后 SMA 表达几乎没有变化。与 NEC 相比，SMA(+)TEC 在划痕愈合实验中的迁移能力降低了 40%，并且在受到 TGFβ挑战时在体外形成更稳定的血管样网络。使用 ZsGreen(Cdh5-Cre)报告小鼠进行的谱系追踪证实，乳腺肿瘤中的只有一部分血管含有 SMA(+)TEC，这表明并非所有内皮细胞（EC）在体内对 TGFβ的反应完全相同。事实上，对 84 个 TGFβ 调节的靶基因的研究表明，在 TGFβ刺激的 NEC 和 TEC 培养物中存在完全不同的遗传特征。最后，我们发现碱性成纤维细胞生长因子（bFGF）对许多 TGFβ 调节的基因具有强大的抑制作用，但与 TGFβ 一起作用以上调其他基因。受到 TGFβ 挑战的 EC 会分泌 bFGF，该因子会在次级培养物中阻断 SMA 的表达，这表明存在阻止间充质分化的细胞自主或侧向抑制机制。总之，我们的结果表明，TGFβ 驱动的 EndMT 产生了具有不同功能的 EC 表型谱，这可能为肿瘤血管的可塑性和异质性提供基础。
