Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, New Orleans, LA.
Hepatology. 2019 Apr;69(4):1549-1563. doi: 10.1002/hep.30153. Epub 2018 Dec 31.
Functions of transforming growth factor-β (TGF-β) in the liver vary depending on specific cell types and their temporal response to TGF-β during different stages of hepatocarcinogenesis (HCG). Through analysis of tumor tissues from hepatocellular carcinoma (HCC) patients, we were able to cluster hepatic epithelial cell-derived TGF-β gene signatures in association with distinct clinical prognoses. To delineate the role of hepatic epithelial TGF-β signaling in HCC development, we used an experimental system in which tumor-initiating hepatocytes (TICs) were isolated from TGF-β receptor II floxed mice (Tgfbr2 ) and transplanted into syngeneic C57BL/6J mice by splenic injection. Recipient mice were then administered Cre-expressing adenovirus (Ad-Cre) to inactivate Tgfbr2 in transplanted TICs. After latency, Tgfbr2-inactivated TICs formed larger and more tumor nodules in recipient livers compared to TICs without Tgfbr2 inactivation. In vitro analyses revealed that treatment of cultured TICs with TGF-β inhibited expression of progenitor cell factors (including SRY (sex determining region Y)-box 2 [Sox2]). RNA sequencing (RNA-seq) analysis identified H19 as one of the most up-regulated long noncoding RNA (lncRNA) in association with Tgfbr2 inactivation in TICs. Tgfbr2 inactivation by Ad-Cre led to a 5-fold increase of H19 expression in TICs. Accordingly, TGF-β treatment reduced H19 expression. We observed that forced overexpression of Sox2 in TICs increased transcription of H19, whereas knockdown of Sox2 decreased it. Furthermore, depletion of H19 reduced the progenitor property of TICs in vitro and decreased their tumorigenic potential in vivo. Finally, we observed a low level of H19 mRNA expression in human HCC tissues from patients with the epithelial TGF-β gene signature in association with favorable prognosis. Conclusion: Our findings describe a TGF-β and H19 signaling axis by Sox2 in TICs that importantly regulates HCG.
转化生长因子-β（TGF-β）在肝脏中的功能因特定细胞类型及其在肝癌发生（HCC）不同阶段对 TGF-β的时空反应而异。通过分析 HCC 患者的肿瘤组织，我们能够将与不同临床预后相关的肝上皮细胞衍生的 TGF-β基因特征聚类在一起。为了描绘肝上皮 TGF-β信号在 HCC 发展中的作用，我们使用了一种实验系统，其中从 TGF-β受体 II 基因敲除（Tgfbr2 ）小鼠中分离肿瘤起始肝细胞（TICs），并通过脾内注射将其移植到同基因 C57BL/6J 小鼠中。然后，给接受者小鼠施用表达 Cre 的腺病毒（Ad-Cre）以在移植的 TIC 中失活 Tgfbr2 。潜伏期后，与未失活 Tgfbr2 的 TIC 相比，Tgfbr2 失活的 TIC 在受体肝脏中形成更大和更多的肿瘤结节。体外分析表明，用 TGF-β处理培养的 TIC 会抑制祖细胞因子（包括性别决定区 Y 框 2 [Sox2]）的表达。RNA 测序（RNA-seq）分析表明，H19 是与 TIC 中 Tgfbr2 失活相关的上调最显著的长非编码 RNA（lncRNA）之一。Ad-Cre 导致 TIC 中 H19 的表达增加了 5 倍。相应地，TGF-β处理降低了 H19 的表达。我们观察到 Sox2 在 TIC 中的强制过表达增加了 H19 的转录，而 Sox2 的敲低则降低了它。此外，H19 的耗竭降低了 TIC 在体外的祖细胞特性，并降低了它们在体内的致瘤潜能。最后，我们观察到具有上皮 TGF-β基因特征的患者的人 HCC 组织中 H19 mRNA 表达水平较低，与有利的预后相关。结论：我们的研究结果描述了 Sox2 在 TICs 中 TGF-β 和 H19 信号轴，该信号轴对 HCC 具有重要的调控作用。
