Wang Meili, Zhao Xiulan, Zhu Dongwang, Liu Tieju, Liang Xiaohui, Liu Fang, Zhang Yanhui, Dong Xueyi, Sun Baocun
Department of Pathology, Tianjin Medical University, Tianjin, 300070, China.
Department of Pathology, General Hospital of Tianjin Medical University, Tianjin, 300052, China.
J Exp Clin Cancer Res. 2017 Apr 27;36(1):60. doi: 10.1186/s13046-017-0533-1.
The incidence and mortality rates of hepatocellular carcinoma (HCC) have steadily increased in recent years. A hypoxic microenvironment is one of the most important characteristics of solid tumors which has been shown to promote tumor metastasis, epithelial-mesenchymal transition and angiogenesis. Epithelial-mesenchymal transition and vasculogenic mimicry have been regarded as crucial contributing factors to cancer progression. HIF-1α functions as a master transcriptional regulator in the adaptive response to hypoxia. Lysyl oxidases like 2 (LOXL2) is a member of the lysyl oxidase family, which main function is to catalyze the covalent cross-linkages of collagen and elastin in the extracellular matrix. Recent work has demonstrated that HIF-1α promotes the expression of LOXL2, which is believed to amplify tumor aggressiveness. LOXL2 has shown to promote metastasis and is correlated with poor prognosis in hepatocellular carcinoma. The purpose of our study is to explore the role of HIF-1α in progression and metastasis of hepatocellular carcinoma by promoting the expression of LOXL2 as well as the potential regulatory mechanism.
HIF-1α, LOXL2 expression and CD31/periodic acid-Schiff double staining in HCC patient samples were examined by immunohistochemical staining. shRNA plasmids against HIF-1α was used to determine whether LOXL2 been increased by HIF-1α. We monitored a series of rescue assays to demonstrate our hypothesis that LOXL2 is required and sufficient for HIF-1α induced EMT and VM formation, which mediates cellular transformation and takes effect in cellular invasion. Then we performed GeneChip® Human Transcriptome Array (HTA) 2.0 in HepG2 cells, HepG2 cells overexpressed LOXL2 and HepG2 cells treated with CoCl.
In clinical HCC tissues, it confirmed a positive relationship between HIF-1α and LOXL2 protein. Importantly, HIF-1α and LOXL2 high expression and the presence of vasculogenic mimicry were correlated to poor prognosis. HIF-1α was found to induce EMT, HCC cell migration, invasion and VM formation by regulating LOXL2. The results of microarray assays were analyzed.
HIF-1α plays an important role in the development of HCC by promoting HCC metastasis, EMT and VM through up-regulating LOXL2. This study highlights the potential therapeutic value of targeting LOXL2 for suppression of HCC metastasis and progression.
近年来，肝细胞癌（HCC）的发病率和死亡率持续上升。缺氧微环境是实体瘤最重要的特征之一，已被证明可促进肿瘤转移、上皮-间质转化和血管生成。上皮-间质转化和血管生成拟态被认为是癌症进展的关键因素。缺氧诱导因子-1α（HIF-1α）在缺氧适应性反应中起主要转录调节作用。赖氨酰氧化酶样2（LOXL2）是赖氨酰氧化酶家族的成员，其主要功能是催化细胞外基质中胶原蛋白和弹性蛋白的共价交联。最近的研究表明，HIF-1α可促进LOXL2的表达，据信这会增强肿瘤的侵袭性。已证明LOXL2可促进转移，且与肝细胞癌的不良预后相关。本研究的目的是探讨HIF-1α通过促进LOXL2的表达在肝细胞癌进展和转移中的作用及其潜在的调控机制。
采用免疫组织化学染色检测HCC患者样本中HIF-1α、LOXL2的表达及CD31/过碘酸希夫双重染色情况。使用针对HIF-1α的短发夹RNA（shRNA）质粒来确定LOXL2是否由HIF-1α上调。我们进行了一系列挽救实验以证明我们的假设，即LOXL2对于HIF-1α诱导的上皮-间质转化和血管生成拟态形成是必需且充分的，这介导了细胞转化并在细胞侵袭中起作用。然后我们在HepG2细胞、过表达LOXL2的HepG2细胞和用氯化钴处理的HepG2细胞中进行了基因芯片人类转录组阵列（HTA）2.0检测。
在临床HCC组织中，证实了HIF-1α与LOXL2蛋白之间呈正相关。重要的是，HIF-1α和LOXL2的高表达以及血管生成拟态的存在与不良预后相关。发现HIF-1α通过调节LOXL2诱导上皮-间质转化、HCC细胞迁移、侵袭和血管生成拟态形成。对微阵列分析结果进行了分析。
HIF-1α通过上调LOXL2促进HCC转移、上皮-间质转化和血管生成拟态，在HCC的发生发展中起重要作用。本研究突出了靶向LOXL2抑制HCC转移和进展的潜在治疗价值。
