SVMS, Faculty of Medicine and Health Sciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UK.
School of Medicine, Biodiscovery Institute, University of Nottingham, Nottingham, NG7 2RD, UK.
Stem Cell Res Ther. 2024 May 1;15(1):128. doi: 10.1186/s13287-024-03724-1.
Testicular germ cell tumours (TGCTs) represent a clinical challenge; they are most prevalent in young individuals and are triggered by molecular mechanisms that are not fully understood. The origin of TGCTs can be traced back to primordial germ cells that fail to mature during embryonic development. These cells express high levels of pluripotency factors, including the transcription factor NANOG which is highly expressed in TGCTs. Gain or amplification of the NANOG locus is common in advanced tumours, suggesting a key role for this master regulator of pluripotency in TGCT stemness and malignancy.
In this study, we analysed the expression of microRNAs (miRNAs) that are regulated by NANOG in TGCTs via integrated bioinformatic analyses of data from The Cancer Genome Atlas and NANOG chromatin immunoprecipitation in human embryonic stem cells. Through gain-of-function experiments, MIR9-2 was further investigated as a novel tumour suppressor regulated by NANOG. After transfection with MIR9-2 mimics, TGCT cells were analysed for cell proliferation, invasion, sensitivity to cisplatin, and gene expression signatures by RNA sequencing.
For the first time, we identified 86 miRNAs regulated by NANOG in TGCTs. Among these, 37 miRNAs were differentially expressed in NANOG-high tumours, and they clustered TGCTs according to their subtypes. Binding of NANOG within 2 kb upstream of the MIR9-2 locus was associated with a negative regulation. Low expression of MIR9-2 was associated with tumour progression and MIR9-2-5p was found to play a role in the control of tumour stemness. A gain of function of MIR9-2-5p was associated with reduced proliferation, invasion, and sensitivity to cisplatin in both embryonal carcinoma and seminoma tumours. MIR9-2-5p expression in TGCT cells significantly reduced the expression of genes regulating pluripotency and cell division, consistent with its functional effect on reducing cancer stemness.
This study provides new molecular insights into the role of NANOG as a key determinant of pluripotency in TGCTs through the regulation of MIR9-2-5p, a novel epigenetic modulator of cancer stemness. Our data also highlight the potential negative feedback mediated by MIR9-2-5p on NANOG expression, which could be exploited as a therapeutic strategy for the treatment of TGCTs.
睾丸生殖细胞肿瘤（TGCT）是一个临床挑战；它们在年轻人中最为常见，其触发机制尚不完全清楚。TGCT 的起源可以追溯到胚胎发育过程中未能成熟的原始生殖细胞。这些细胞表达高水平的多能性因子，包括转录因子 NANOG，其在 TGCT 中高度表达。NANOG 基因座的获得或扩增在晚期肿瘤中很常见，这表明该多能性主调控因子在 TGCT 干细胞特性和恶性肿瘤中起着关键作用。
在这项研究中，我们通过整合癌症基因组图谱（The Cancer Genome Atlas）的数据和人类胚胎干细胞中 NANOG 染色质免疫沉淀的生物信息学分析，分析了 NANOG 调控的 microRNAs（miRNAs）在 TGCT 中的表达。通过 gain-of-function 实验，进一步研究了 MIR9-2 作为受 NANOG 调控的新型肿瘤抑制因子。转染 MIR9-2 模拟物后，通过 RNA 测序分析 TGCT 细胞的增殖、侵袭、顺铂敏感性和基因表达特征。
我们首次鉴定了 86 种在 TGCT 中受 NANOG 调控的 miRNAs。其中，37 种 miRNAs 在 NANOG 高表达的肿瘤中表达差异，它们根据亚型聚类 TGCT。NANOG 在 MIR9-2 基因座上游 2kb 内的结合与负调控相关。MIR9-2 的低表达与肿瘤进展相关，并且发现 MIR9-2-5p 在控制肿瘤干细胞特性方面发挥作用。MIR9-2-5p 的功能获得与胚胎癌和精原细胞瘤肿瘤中的增殖、侵袭和顺铂敏感性降低有关。MIR9-2-5p 在 TGCT 细胞中的表达显著降低了调节多能性和细胞分裂的基因的表达，与它降低癌症干细胞特性的功能效应一致。
本研究通过调控 MIR9-2-5p，为 NANOG 作为 TGCT 多能性关键决定因素的作用提供了新的分子见解，MIR9-2-5p 是一种新型的癌症干细胞表观遗传调节剂。我们的数据还强调了 MIR9-2-5p 对 NANOG 表达的潜在负反馈作用，这可能被用作治疗 TGCT 的治疗策略。
