BACKGROUND: Glioblastoma (GBM) is the most malignant primary brain tumor. Relapse occurs regularly, and the clinical behavior seems to be due to a therapy-resistant subpopulation of glioma-initiating cells that belong to the group of cancer stem cells. Aldehyde dehydrogenase (ALDH) has been identified as a marker for this cell population, and we have shown previously that ALDH1A3-positive GBM cells are more resistant against temozolomide (TMZ) treatment. However, it is still unclear how ALDH expression mediates chemoresistance. MATERIALS AND METHODS: ALDH1A3 expression was analyzed in 112 specimens from primary and secondary surgical resections of 56 patients with GBM (WHO grade IV). All patients received combined adjuvant radiochemotherapy. For experimental analysis, CRISPR-Cas9–induced knockout cells from three established GBM cell lines (LN229, U87MG, T98G) and two glioma stem-like cell lines were investigated after TMZ treatment. RESULTS: ALDH1A3 knockout cells were more sensitive to TMZ, and oxidative stress seemed to be the molecular process where ALDH1A3 exerts its role in resistance against TMZ. Oxidative stress led to lipid peroxidation, yielding active aldehydes that were detoxified by ALDH enzymatic activity. During the metabolic process, autophagy was induced leading to downregulation of the enzyme, but ALDH1A3 is upregulated to even higher expression levels after finishing the TMZ therapy in vitro. Recurrent GBMs show significantly higher ALDH1A3 expression than the respective samples from the primary tumor, and patients suffering from GBM with high ALDH1A3 expression showed a shorter median survival time (12 months vs 21 months, P < .05). CONCLUSION: Oxidative stress is an important and clinically relevant component of TMZ-induced therapeutic effects. Cytotoxicity seems to be mediated by aldehydes resulting from lipid peroxidation, and ALDH1A3 is able to reduce the number of toxic aldehydes. Therefore, we present a molecular explanation of the role of ALDH1A3 in therapeutic resistance of human GBM cells.

背景：胶质母细胞瘤（GBM）是最恶性的原发性脑肿瘤。复发定期发生，并且临床行为似乎归因于属于癌症干细胞组的神经胶质瘤起始细胞的抗治疗亚群。醛脱氢酶（ALDH）已被鉴定为该细胞群的标志物，并且我们之前已经证明ALDH1A3阳性GBM细胞对替莫唑胺（TMZ）的治疗更具抵抗力。然而，仍不清楚ALDH表达如何介导化学抗性。材料和方法：在56例GBM（WHO IV级）患者的初次和二次手术切除的112个标本中分析了ALDH1A3的表达。所有患者均接受联合辅助放化疗。为了进行实验分析，TMZ处理后，研究了来自三个已建立的GBM细胞系（LN229，U87MG，T98G）和两个神经胶质瘤干样细胞系的CRISPR-Cas9诱导的敲除细胞。结果：ALDH1A3敲除细胞对TMZ更为敏感，氧化应激似乎是ALDH1A3发挥其对TMZ抗性的分子过程。氧化应激导致脂质过氧化，产生被ALDH酶活性解毒的活性醛。在代谢过程中，自噬被诱导导致酶的下调，但是在体外完成TMZ治疗后，ALDH1A3被上调至更高的表达水平。复发性GBMs的ALDH1A3表达明显高于原发肿瘤的相应样品，患有ALDM1A3高表达的GBM患者的中位生存时间较短（12个月比21个月，P  <.05）。结论：氧化应激是TMZ诱导的治疗效果的重要且与临床相关的组成部分。细胞毒性似乎是由脂质过氧化作用产生的醛介导的，ALDH1A3能够减少毒性醛的数量。因此，我们提出ALDH1A3在人GBM细胞治疗耐药性中作用的分子解释。