Krkoška Martin, Tylichová Zuzana, Zatloukalová Pavlína, Müller Petr, Vojtěšek Bořivoj, Coates Philip John
Research Centre for Applied Molecular Oncology, Masaryk Memorial Cancer Institute, Žlutý kopec 7, Brno, 656 53, Czech Republic.
BMC Cancer. 2025 Jul 1;25(1):1085. doi: 10.1186/s12885-025-14460-x.
Cancer stem-like cells (CSCs) represent a subset of tumor cells that have the ability to self-renew, a long lifespan and a relatively quiescent phenotype, and show resistance to conventional therapies. Various markers are used to identify CSCs, and have shown that different CSC subtypes may be present within a tumor. One functional property of CSCs is their relative lack of proteasomal activity compared to the tumor bulk.
We introduced an unstable fluorescent molecule into FaDu oropharyngeal squamous cell carcinoma cells and analyzed the association of proteasome activity with aldehydehyde dehydrogenase (ALDH) activity as another common CSC marker, and with other stem-cell related properties of glucose metabolism. We also analyzed publicly available gene expression profiling data of ALDH CSCs for alterations in mRNAs associated with proteostasis.
We show that FaDu CSCs identified by low proteasome activity are associated with the population identified by high ALDH activity. Futher characterization shows that these CSCs have a relatively high mitochondrial membrane potential and low levels of glucose transporter, indicating a non-Warburg metabolic phenotype. We also show that proteasome-low FaDu CSCs exhibit decreased rates of protein synthesis. Gene expression profiling of other cancer cell lines reveal common statistically significant differences in proteostasis in ALDH CSCs compared to the bulk of the tumor cells, including reduced levels of Hsp70 and/or Hsp90 in CSCs defined by ALDH, together with reduced levels of UCHL5 mRNA.
These data provide additional insights into the functional characteristics of proteasome-low/ALDH-high CSCs, indicating a metabolic phenotype of reduced reliance on aerobic glycolysis and a decreased protein synthesis rate. We also identify specific chaperone and ubiquitin ligase activities that can be used to identify CSCs, with corresponding implications for therapeutic strategies that target CSCs through their altered metabolic properties.
癌症干细胞（CSCs）是肿瘤细胞的一个亚群，具有自我更新能力、较长的寿命和相对静止的表型，并且对传统疗法具有抗性。多种标志物被用于识别CSCs，且已表明肿瘤内可能存在不同的CSC亚型。CSCs的一个功能特性是与肿瘤主体相比，其蛋白酶体活性相对缺乏。
我们将一种不稳定的荧光分子导入FaDu口咽鳞状细胞癌细胞中，并分析蛋白酶体活性与醛脱氢酶（ALDH）活性（作为另一种常见的CSC标志物）以及与葡萄糖代谢的其他干细胞相关特性之间的关联。我们还分析了公开可用的ALDH CSCs基因表达谱数据，以寻找与蛋白质稳态相关的mRNA变化。
我们发现，蛋白酶体活性低所识别出的FaDu CSCs与ALDH活性高所识别出的细胞群体相关。进一步的特征分析表明，这些CSCs具有相对较高的线粒体膜电位和较低水平的葡萄糖转运蛋白，表明其具有非瓦伯格代谢表型。我们还表明，蛋白酶体活性低的FaDu CSCs蛋白质合成速率降低。对其他癌细胞系的基因表达谱分析显示，与肿瘤细胞主体相比，ALDH CSCs在蛋白质稳态方面存在常见的统计学显著差异，包括ALDH定义的CSCs中Hsp70和/或Hsp90水平降低，以及UCHL5 mRNA水平降低。
这些数据为蛋白酶体活性低/ALDH活性高的CSCs的功能特性提供了更多见解，表明其代谢表型为对有氧糖酵解的依赖性降低且蛋白质合成速率下降。我们还确定了可用于识别CSCs的特定伴侣蛋白和泛素连接酶活性，这对通过改变其代谢特性靶向CSCs的治疗策略具有相应的启示。
