Department of Pathology, The University of Hong Kong, Hong Kong; State Key Laboratory of Liver Research, The University of Hong Kong, Hong Kong.
State Key Laboratory of Liver Research, The University of Hong Kong, Hong Kong; Department of Surgery, The University of Hong Kong, Hong Kong.
J Hepatol. 2022 Aug;77(2):383-396. doi: 10.1016/j.jhep.2022.02.018. Epub 2022 Feb 25.
BACKGROUND & AIMS: The highly proliferative nature of hepatocellular carcinoma (HCC) frequently results in a hypoxic intratumoural microenvironment, which creates a therapeutic challenge owing to a lack of mechanistic understanding of the phenomenon. We aimed to identify critical drivers of HCC development and progression in the hypoxic microenvironment.
We performed integrative analysis of multiple transcriptomic and genomic profiles specific for HCC and hypoxia and identified the Ephrin-A3/Eph receptor A2 (EphA2) axis as a clinically relevant and hypoxia-inducible signalling axis in HCC. The functional significance and mechanistic consequences of the Ephrin-A3/EphA2 axis were examined in EFNA3- and EPHA2- knockdown/overexpressing HCC cells. The potential downstream pathways were investigated by transcriptome sequencing, quantitative reverse-transcription PCR, western blotting analysis and metabolomics.
EFNA3 was frequently upregulated in HCC and its overexpression was associated with more aggressive tumour behaviours. HIF-1α directly and positively regulated EFNA3 expression under hypoxia. EFNA3 functionally contributed to self-renewal, proliferation and migration in HCC cells. EphA2 was identified as a key functional downstream mediator of EFNA3. Functional characterisation of the Ephrin-A3/EphA2 forward-signalling axis demonstrated a promotion of self-renewal ability and tumour initiation. Mechanistically, the Ephrin-A3/EphA2 axis promoted the maturation of SREBP1 and expression of its transcriptional target, ACLY, was significantly associated with the expression of EFNA3 and hypoxia markers in clinical cohorts. The metabolic signature of EPHA2 and ACLY stable knockdown HCC cells demonstrated significant overlap in fatty acid, cholesterol and tricarboxylic acid cycle metabolite profiles. ACLY was confirmed to mediate the self-renewal function of the Ephrin-A3/EphA2 axis.
Our findings revealed the novel role of the Ephrin-A3/EphA2 axis as a hypoxia-sensitive modulator of HCC cell metabolism and a key contributor to HCC initiation and progression.
Hepatocellular carcinoma (HCC) is a fast-growing tumour; hence, areas of the tumour often have insufficient vasculature and become hypoxic. The presence of hypoxia within tumours has been shown to negatively impact on the survival of patients with tumours, including HCC. Herein, we identified the Ephrin-A3/EphA2 axis as a key functional driver of tumour initiation and progression in response to hypoxia. Additionally, we showed that SREBP1-ACLY-mediated metabolic rewiring was an important downstream effector that induced cancer stemness in response to Ephrin-A3/EphA2 forward-signalling.
肝细胞癌（HCC）具有高度增殖性，常导致肿瘤内缺氧微环境，由于对这一现象缺乏机制上的了解，这给治疗带来了挑战。本研究旨在确定缺氧微环境中 HCC 发生和进展的关键驱动因素。
我们对 HCC 和缺氧特异性的多个转录组和基因组图谱进行了综合分析，确定 Ephrin-A3/Eph 受体 A2（EphA2）轴是 HCC 中具有临床相关性和缺氧诱导的信号轴。在 EFNA3 和 EPHA2 敲低/过表达 HCC 细胞中，检测 Ephrin-A3/EphA2 轴的功能意义和机制后果。通过转录组测序、定量逆转录 PCR、Western blot 分析和代谢组学研究潜在的下游途径。
EFNA3 在 HCC 中频繁上调，其过表达与更具侵袭性的肿瘤行为相关。HIF-1α 在缺氧下直接正向调节 EFNA3 的表达。EFNA3 在 HCC 细胞中具有促进自我更新、增殖和迁移的功能。EphA2 被鉴定为 EFNA3 的关键功能下游介质。Ephrin-A3/EphA2 正向信号轴的功能特征表明其促进了自我更新能力，促进了肿瘤起始。在机制上，Ephrin-A3/EphA2 轴促进了 SREBP1 的成熟，其转录靶标 ACLY 的表达与临床队列中 EFNA3 和缺氧标志物的表达显著相关。EPHA2 和 ACLY 稳定敲低 HCC 细胞的代谢特征显示脂肪酸、胆固醇和三羧酸循环代谢物谱有明显重叠。ACLY 被证实介导 Ephrin-A3/EphA2 轴的自我更新功能。
我们的研究结果揭示了 Ephrin-A3/EphA2 轴作为 HCC 细胞代谢的缺氧敏感调节剂和 HCC 起始和进展的关键贡献者的新作用。
肝细胞癌（HCC）是一种快速生长的肿瘤；因此，肿瘤的某些区域往往血管不足，导致缺氧。肿瘤内缺氧的存在已被证明对包括 HCC 在内的肿瘤患者的生存产生负面影响。在此，我们确定 Ephrin-A3/EphA2 轴是对缺氧反应中肿瘤起始和进展的关键功能驱动因素。此外，我们表明，SREBP1-ACLY 介导的代谢重编程是 Ephrin-A3/EphA2 正向信号诱导癌症干性的重要下游效应子。
