Department of Gastroenterology and Hepatology, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.
Department of General Surgery, Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.
Hepatology. 2018 Jun;67(6):2226-2243. doi: 10.1002/hep.29678. Epub 2018 Apr 19.
High invasiveness is a hallmark of human hepatocellular carcinoma (HCC). Large tumors predict invasion and metastasis. Epithelial-mesenchymal transition (EMT) is crucial for cancer invasion and metastasis. However, the mechanisms whereby large tumors tend to undergo EMT remain unclear. We conducted a subgenome-wide screen and identified KLHL23 as an HCC invasion suppressor by inhibiting EMT. KLHL23 binds to actin and suppresses actin polymerization. KLHL23 silencing induced filopodium and lamellipodium formation. Moreover, EMT was suppressed by KLHL23 through its action on actin dynamics. Traditionally, actin cytoskeleton remodeling is downstream of EMT reprogramming. It is therefore intriguing to ask why and how KLHL23 inversely regulates EMT. Activation of actin cytoskeleton remodeling by either KLHL23 silencing or treatment with actin cytoskeleton modulators augmented cellular hypoxic responses in a cell-density-dependent manner, resulting in hypoxia-inducible factor (HIF) and Notch signals and subsequent EMT. Environmental hypoxia did not induce EMT unless actin cytoskeleton remodeling was simultaneously activated and only when cells were at high density. The resulting EMT was reversed by either adenosine 5'-triphosphate supplementation or actin polymerization inhibitors. Down-regulation of KLHL23 was associated with invasion, metastasis, and poor prognosis of HCC and pancreatic cancer. Correlations of tumor size with EMT and inverse association of expression of KLHL23 with HIF/Notch signals were further validated in patient-derived xenograft HCCs in mice.
Simultaneously activation of actin cytoskeleton remodeling by intrinsic (such as KLHL23 down-regulation) or microenvironment cues is crucial for cell-density-dependent and hypoxia-mediated EMT, providing a mechanistic link between large tumor size and invasion/metastasis. Our findings provide a means of developing the prevention and treatment strategies for tumor invasion and metastasis. (Hepatology 2018;67:2226-2243).
人类肝细胞癌（HCC）的高侵袭性是其标志。大肿瘤预示着侵袭和转移。上皮-间充质转化（EMT）对于癌症的侵袭和转移至关重要。然而，大肿瘤倾向于发生 EMT 的机制尚不清楚。我们进行了全基因组亚克隆筛选，发现 KLHL23 通过抑制 EMT 成为 HCC 侵袭抑制剂。KLHL23 与肌动蛋白结合并抑制肌动蛋白聚合。KLHL23 沉默诱导丝状伪足和片状伪足的形成。此外，KLHL23 通过其对肌动蛋白动力学的作用抑制 EMT。传统上，肌动蛋白细胞骨架重塑是 EMT 重编程的下游。因此，令人好奇的是 KLHL23 为什么以及如何反向调节 EMT。通过 KLHL23 沉默或肌动蛋白细胞骨架调节剂处理激活肌动蛋白细胞骨架重塑，以细胞密度依赖的方式增强细胞缺氧反应，导致缺氧诱导因子（HIF）和 Notch 信号，随后发生 EMT。除非同时激活肌动蛋白细胞骨架重塑，并且只有在细胞密度高时，环境缺氧才会诱导 EMT。缺氧诱导的 EMT 可通过添加三磷酸腺苷或肌动蛋白聚合抑制剂来逆转。KLHL23 的下调与 HCC 和胰腺癌的侵袭、转移和预后不良有关。在小鼠来源的 HCC 患者衍生异种移植肿瘤中进一步验证了肿瘤大小与 EMT 的相关性以及 KLHL23 表达与 HIF/Notch 信号的负相关。
通过内在（如 KLHL23 下调）或微环境线索同时激活肌动蛋白细胞骨架重塑对于细胞密度依赖性和缺氧介导的 EMT 至关重要，为大肿瘤大小与侵袭/转移之间提供了机制联系。我们的研究结果为开发肿瘤侵袭和转移的预防和治疗策略提供了依据。（Hepatology 2018;67:2226-2243）。
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