BACKGROUND Quiescent/slow cycling cells have been identified in several tumors and correlated with therapy resistance. However, the features of chemoresistant populations and the molecular factors linking quiescence to chemoresistance are largely unknown. METHODS A population of chemoresistant quiescent/slow cycling cells was isolated through PKH26 staining (which allows to separate cells on the basis of their proliferation rate) from colorectal cancer (CRC) xenografts and subjected to global gene expression and pathway activation analyses. Factors expressed by the quiescent/slow cycling population were analyzed through lentiviral overexpression approaches for their ability to induce a dormant chemoresistant state both in vitro and in mouse xenografts. The correlation between quiescence-associated factors, CRC consensus molecular subtype and cancer prognosis was analyzed in large patient datasets. RESULTS Untreated colorectal tumors contain a population of quiescent/slow cycling cells with stem cell features (quiescent cancer stem cells, QCSCs) characterized by a predetermined mesenchymal-like chemoresistant phenotype. QCSCs expressed increased levels of ZEB2, a transcription factor involved in stem cell plasticity and epithelial-mesenchymal transition (EMT), and of antiapototic factors pCRAF and pASK1. ZEB2 overexpression upregulated pCRAF/pASK1 levels resulting in increased chemoresistance, enrichment of cells with stemness/EMT traits and proliferative slowdown of tumor xenografts. In parallel, chemotherapy treatment of tumor xenografts induced the prevalence of QCSCs with a stemness/EMT phenotype and activation of the ZEB2/pCRAF/pASK1 axis, resulting in a chemotherapy-unresponsive state. In CRC patients, increased ZEB2 levels correlated with worse relapse-free survival and were strongly associated to the consensus molecular subtype 4 (CMS4) characterized by dismal prognosis, decreased proliferative rates and upregulation of EMT genes. CONCLUSIONS These results show that chemotherapy-naive tumors contain a cell population characterized by a coordinated program of chemoresistance, quiescence, stemness and EMT. Such population becomes prevalent upon drug treatment and is responsible for chemotherapy resistance, thus representing a key target for more effective therapeutic approaches.

中文翻译：

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先前存在的具有干细胞和间充质特征的ZEB2 +静止细胞群体决定了结直肠癌的化学耐药性。

背景技术已经在几种肿瘤中鉴定出静止/慢循环细胞，并且与治疗抗性相关。但是，化学抗性种群的特征以及将静止性与化学抗性联系起来的分子因素在很大程度上是未知的。方法通过大肠癌（CRC）异种移植物通过PKH26染色（允许根据其增殖速率分离细胞）分离化学抗性的静态/慢循环细胞，并进行整体基因表达和途径激活分析。通过慢病毒过度表达方法分析了静态/慢循环人口所表达的因子在体外和小鼠异种移植物中诱导休眠的化学抗性状态的能力。静态相关因素之间的相关性，在大型患者数据集中分析了CRC共有分子亚型和癌症预后。结果未经治疗的结直肠肿瘤包含具有以预定的间充质样化学抗性表型为特征的干细胞特征（静态癌症干细胞，QCSC）的静态/慢循环细胞。QCSCs表达的干细胞可塑性和上皮-间质转化（EMT）所涉及的转录因子ZEB2以及抗凋亡因子pCRAF和pASK1的表达水平均升高。ZEB2的过表达上调了pCRAF / pASK1的水平，导致化学抗性增加，具有干性/ EMT性状的细胞富集以及肿瘤异种移植物的增殖减慢。同时，肿瘤异种移植物的化学疗法诱导了QCSC的流行，其具有茎干/ EMT表型和ZEB2 / pCRAF / pASK1轴激活，导致化疗无反应状态。在CRC患者中，ZEB2水平升高与无复发生存率差相关，并且与以不良预后，增殖率降低和EMT基因上调为特征的共有分子亚型4（CMS4）密切相关。结论这些结果表明，未经化学疗法治疗的肿瘤包含以化学抗性，静止，干性和EMT协调程序为特征的细胞群。这种人群在药物治疗中变得普遍，并导致化学疗法的耐药性，因此代表了更有效治疗方法的关键目标。增加的ZEB2水平与较差的无复发生存率相关，并且与以不良预后，增生率降低和EMT基因上调为特征的共有分子亚型4（CMS4）密切相关。结论这些结果表明，未经化学疗法治疗的肿瘤包含以化学抗性，静止，干性和EMT协调程序为特征的细胞群。这种人群在药物治疗中变得普遍，并导致化学疗法的耐药性，因此代表了更有效治疗方法的关键目标。增加的ZEB2水平与较差的无复发生存率相关，并且与以不良预后，增生率降低和EMT基因上调为特征的共有分子亚型4（CMS4）密切相关。结论这些结果表明，未经化学疗法治疗的肿瘤包含以化学抗性，静止，干性和EMT协调程序为特征的细胞群。这种人群在药物治疗中变得普遍，并导致化学疗法的耐药性，因此代表了更有效治疗方法的关键目标。