Abstract

Background

Glioblastoma is associated with poor prognosis and high mortality. Although the use of first-line temozolomide can reduce tumor growth, therapy-induced stress drives stem cells out of quiescence, leading to chemoresistance and glioblastoma recurrence. The specificity protein 1 (Sp1) transcription factor is known to protect glioblastoma cells against temozolomide; however, how tumor cells hijack this factor to gain resistance to therapy is not known.

Methods

Sp1 acetylation in temozolomide-resistant cells and stemlike tumorspheres was analyzed by immunoprecipitation and immunoblotting experiments. Effects of the histone deacetylase (HDAC)/Sp1 axis on malignant growth were examined using cell proliferation–related assays and in vivo experiments. Furthermore, integrative analysis of gene expression with chromatin immunoprecipitation sequencing and the recurrent glioblastoma omics data were also used to further determine the target genes of the HDAC/Sp1 axis.

Results

We identified Sp1 as a novel substrate of HDAC6, and observed that the HDAC1/2/6/Sp1 pathway promotes self-renewal of malignancy by upregulating B cell-specific Mo-MLV integration site 1 (BMI1) and human telomerase reverse transcriptase (hTERT), as well as by regulating G2/M progression and DNA repair via alteration of the transcription of various genes. Importantly, HDAC1/2/6/Sp1 activation is associated with poor clinical outcome in both glioblastoma and low-grade gliomas. However, treatment with azaindolyl sulfonamide, a potent HDAC6 inhibitor with partial efficacy against HDAC1/2, induced G2/M arrest and senescence in both temozolomide-resistant cells and stemlike tumorspheres.

Conclusion

Our study uncovers a previously unknown regulatory mechanism in which the HDAC6/Sp1 axis induces cell division and maintains the stem cell population to fuel tumor growth and therapeutic resistance.

中文翻译：

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HDAC1/2/6 和 Sp1 激活的增加是胶质母细胞瘤治疗耐药和肿瘤生长的基础。

 抽象的

 背景

胶质母细胞瘤与不良预后和高死亡率相关。尽管使用一线替莫唑胺可以减少肿瘤生长，但治疗引起的应激会使干细胞脱离静止状态，导致化疗耐药和胶质母细胞瘤复发。已知特异性蛋白 1 (Sp1) 转录因子可保护胶质母细胞瘤细胞免受替莫唑胺的侵害；然而，肿瘤细胞如何劫持该因子以获得对治疗的抵抗力尚不清楚。

 方法

通过免疫沉淀和免疫印迹实验分析了替莫唑胺耐药细胞和干细胞瘤球中的 Sp1 乙酰化。使用细胞增殖相关测定和体内实验检查组蛋白脱乙酰酶 (HDAC)/Sp1 轴对恶性生长的影响。此外，还利用染色质免疫沉淀测序和复发性胶质母细胞瘤组学数据对基因表达进行综合分析，进一步确定HDAC/Sp1轴的靶基因。

 结果

我们确定 Sp1 是 HDAC6 的一种新底物，并观察到 ​​HDAC1/2/6/Sp1 通路通过上调 B 细胞特异性 Mo-MLV 整合位点 1 (BMI1) 和人端粒酶逆转录酶 (hTERT) 来促进恶性肿瘤的自我更新。 ），以及通过改变各种基因的转录来调节 G2/M 进程和 DNA 修复。重要的是，HDAC1/2/6/Sp1 激活与胶质母细胞瘤和低级别胶质瘤的不良临床结果相关。然而，氮杂吲哚基磺酰胺（一种有效的 HDAC6 抑制剂，对 HDAC1/2 具有部分功效）治疗可诱导替莫唑胺耐药细胞和干细胞样肿瘤球的 G2/M 期停滞和衰老。

 结论

我们的研究揭示了一种以前未知的调节机制，其中 HDAC6/Sp1 轴诱导细胞分裂并维持干细胞群以促进肿瘤生长和治疗耐药性。