(1) Background: The sensitivity of head and neck squamous cell carcinoma (HNSCC) to ionizing radiation, among others, is determined by the number of cells with high clonogenic potential and stem-like features. These cellular characteristics are dynamically regulated in response to treatment and may lead to an enrichment of radioresistant cells with a cancer stem cell (CSC) phenotype. Epigenetic mechanisms, particularly DNA and histone methylation, are key regulators of gene-specific transcription and cellular plasticity. Therefore, we hypothesized that specific epigenetic targeting may prevent irradiation-induced plasticity and may sensitize HNSCC cells to radiotherapy. (2) Methods: We compared the DNA methylome and intracellular concentrations of tricarboxylic acid cycle metabolites in radioresistant FaDu and Cal33 cell lines with their parental controls, as well as aldehyde dehydrogenase (ALDH)-positive CSCs with negative controls. Moreover, we conducted a screen of a chemical library targeting enzymes involved in epigenetic regulation in combination with irradiation and analyzed the clonogenic potential, sphere formation, and DNA repair capacity to identify compounds with both radiosensitizing and CSC-targeting potential. (3) Results: We identified the histone demethylase inhibitor GSK-J1, which targets UTX (KDM6A) and JMJD3 (KDM6B), leading to increased H3K27 trimethylation, heterochromatin formation, and gene silencing. The clonogenic survival assay after siRNA-mediated knock-down of both genes radiosensitized Cal33 and SAS cell lines. Moreover, highKDM6Aexpression in tissue sections of patients with HNSCC was associated with improved locoregional control after primary (n= 137) and post-operative (n= 187) radio/chemotherapy. Conversely, highKDM6Bexpression was a prognostic factor for reduced overall survival. (4) Conclusions: Within this study, we investigated cellular and molecular mechanisms underlying irradiation-induced cellular plasticity, a key inducer of radioresistance, with a focus on epigenetic alterations. We identified UTX (KDM6A) as a putative prognostic and therapeutic target for HNSCC patients treated with radiotherapy.
（1）背景：头颈部鳞状细胞癌（HNSCC）对电离辐射的敏感性，除其他因素外，取决于具有高克隆形成潜能和干细胞样特征的细胞数量。这些细胞特性在治疗过程中受到动态调控，可能导致具有癌症干细胞（CSC）表型的辐射抗性细胞富集。表观遗传机制，特别是DNA和组蛋白甲基化，是基因特异性转录和细胞可塑性的关键调控因子。因此，我们假设特异性表观遗传靶向干预可能阻止辐射诱导的可塑性，并可能提高HNSCC细胞对放射治疗的敏感性。 （2）方法：我们比较了辐射抗性FaDu和Cal33细胞系与其亲本对照，以及醛脱氢酶（ALDH）阳性CSCs与阴性对照之间的DNA甲基化组和三羧酸循环代谢物的细胞内浓度。此外，我们筛选了靶向表观遗传调控相关酶的化合物库，结合照射处理，通过分析克隆形成潜能、球体形成能力和DNA修复能力，鉴定具有辐射增敏和CSC靶向潜力的化合物。 （3）结果：我们鉴定出组蛋白去甲基化酶抑制剂GSK-J1，其靶向UTX（KDM6A）和JMJD3（KDM6B），导致H3K27三甲基化增加、异染色质形成和基因沉默。通过siRNA介导敲低这两个基因后进行的克隆形成存活实验显示，Cal33和SAS细胞系的辐射敏感性增强。此外，在HNSCC患者组织切片中，高KDM6A表达与初次（n=137）和术后（n=187）放化疗后局部区域控制的改善相关。相反，高KDM6B表达是总生存期降低的预后因素。 （4）结论：在本研究中，我们探讨了辐射诱导细胞可塑性（辐射抗性的关键诱导因素）背后的细胞和分子机制，重点关注表观遗传改变。我们确定UTX（KDM6A）作为接受放射治疗的HNSCC患者的潜在预后和治疗靶点。
Epigenetic Targeting to Overcome Radioresistance in Head and Neck Cancer
肿瘤(癌症)患者之家