Department of Neurosurgery, Second Affiliated Hospital, Institute of Cancer Stem Cell, Dalian Medical University, Dalian, 116027, China.
Laboratory of Pathogenic Biology, College of Basic Medical Science, Dalian Medical University, Dalian, 116027, China.
J Exp Clin Cancer Res. 2019 Jan 18;38(1):23. doi: 10.1186/s13046-019-1034-1.
The dismal prognosis of patients with glioma is largely attributed to cancer stem cells that display pivotal roles in tumour initiation, progression, metastasis, resistance to therapy, and relapse. Therefore, understanding how these populations of cells maintain their stem-like properties is critical in developing effective glioma therapeutics.
RNA sequencing analysis was used to identify genes potentially involved in regulating glioma stem cells (GSCs). Integrin β4 (ITGB4) expression was validated by quantitative real-time PCR (qRT-PCR) and immunohistochemical (IHC) staining. The role of ITGB4 was investigated by flow cytometry, mammosphere formation, transwell, colony formation, and in vivo tumorigenesis assays. The reciprocal regulation between Integrin β4 and KLF4 was investigated by chromatin immunoprecipitation (ChIP), dual-luciferase reporter assay, immunoprecipitation, and in vivo ubiquitylation assays.
In this study, we found that ITGB4 expression was increased in GSCs and human glioma tissues. Upregulation of ITGB4 was correlated with glioma grades. Inhibition of ITGB4 in glioma cells decreased the self-renewal abilities of GSCs and suppressed the malignant behaviours of glioma cells in vitro and in vivo. Further mechanistic studies revealed that KLF4, an important transcription factor, directly binds to the promoter of ITGB4, facilitating its transcription and contributing to increased ITGB4 expression in glioma. Interestingly, this increased expression enabled ITGB4 to bind KLF4, thus attenuating its interaction with its E3 ligase, the von Hippel-Lindau (VHL) protein, which subsequently decreases KLF4 ubiquitination and leads to its accumulation.
Collectively, our data indicate the existence of a positive feedback loop between KLF4 and ITGB4 that promotes GSC self-renewal and gliomagenesis, suggesting that ITGB4 may be a valuable therapeutic target for glioma.
胶质瘤患者的预后惨淡，主要归因于癌症干细胞，这些细胞在肿瘤起始、进展、转移、治疗耐药和复发中起着关键作用。因此，了解这些细胞群体如何维持其干细胞样特性对于开发有效的胶质瘤治疗方法至关重要。
使用 RNA 测序分析鉴定可能参与调节胶质瘤干细胞（GSCs）的基因。通过定量实时 PCR（qRT-PCR）和免疫组织化学（IHC）染色验证整合素 β4（ITGB4）的表达。通过流式细胞术、类器官形成、Transwell、集落形成和体内肿瘤发生测定研究 ITGB4 的作用。通过染色质免疫沉淀（ChIP）、双荧光素酶报告基因测定、免疫沉淀和体内泛素化测定研究 Integrin β4 和 KLF4 之间的相互调节。
在这项研究中，我们发现 ITGB4 在 GSCs 和人胶质瘤组织中表达增加。ITGB4 的上调与胶质瘤分级相关。在胶质瘤细胞中抑制 ITGB4 降低了 GSCs 的自我更新能力，并抑制了胶质瘤细胞在体外和体内的恶性行为。进一步的机制研究表明，KLF4 是一种重要的转录因子，直接结合 ITGB4 的启动子，促进其转录，并导致胶质瘤中 ITGB4 表达增加。有趣的是，这种表达增加使 ITGB4 能够与 KLF4 结合，从而减弱其与 E3 连接酶（VHL 蛋白）的相互作用，随后减少 KLF4 的泛素化并导致其积累。
综上所述，我们的数据表明 KLF4 和 ITGB4 之间存在正反馈环，促进 GSC 自我更新和胶质瘤发生，表明 ITGB4 可能是治疗胶质瘤的有价值的治疗靶点。
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