Owusu Stephenson Boakye, Ekanayake Akalanka B, Tivanski Alexei V, Petronek Michael S
Department of Radiation Oncology, Division of Free Radical and Radiation Biology, University of Iowa, Iowa City, IA 52242, USA.
Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA.
Int J Mol Sci. 2025 May 16;26(10):4755. doi: 10.3390/ijms26104755.
Radiation therapy is a standard of care treatment for patients with glioblastoma. However, patients' survival rate is dismal, with nearly all patients experiencing disease progression after treatment. Enriched iron content associated with increased transferrin receptor (TfR) expression is an indicator of poor glioblastoma patient outcomes; however, the underlying contributions to tumor progression remain elusive. The goal of this present study is to understand how iron metabolism in glioma contributes to radiation-induced glioblastoma cell motility. U251 and a doxycycline-inducible ferritin heavy chain overexpressing U251 (U251 FtH) cell line were used. For in vitro studies, cells were irradiated with 2 Gy using a Cs source, and after 72 h, atomic force microscopy (AFM) nanoindentation was employed to assess changes in cell stiffness following irradiation. Cell motility was studied using temporal confocal microscopy. For in vivo studies, U251 cells were grown in the rear flanks of female nude athymic mice, and the tumor was irradiated with five fractions of 2 Gy (10 Gy). The tumors were then imaged using a GE 7T small animal MRI to assess changes in T2* MRI, and colorimetric analysis of labile iron was performed using ferrozine. Following irradiation, a biomechanical shift characterized by decreased cell stiffness along with increased cell motility occurred in U251 cells, which corresponded to increased TfR expression. FtH overexpression completely reversed the enhanced cell motility following irradiation. Irradiation of U251 tumors induced the same iron metabolic shift. Interestingly, the change in labile iron in U251 tumors corresponded with an increase in T2* relaxation times, suggesting that T2* mapping may serve as a surrogate marker for assessing radiation-induced changes in iron metabolism.
放射治疗是胶质母细胞瘤患者的标准治疗方法。然而，患者的生存率很低，几乎所有患者在治疗后都会出现疾病进展。与转铁蛋白受体（TfR）表达增加相关的铁含量升高是胶质母细胞瘤患者预后不良的一个指标；然而，其对肿瘤进展的潜在作用仍不清楚。本研究的目的是了解胶质瘤中的铁代谢如何促进辐射诱导的胶质母细胞瘤细胞运动。使用了U251细胞系和强力霉素诱导的铁蛋白重链过表达的U251（U251 FtH）细胞系。在体外研究中，使用铯源对细胞进行2 Gy的照射，72小时后，采用原子力显微镜（AFM）纳米压痕技术评估照射后细胞硬度的变化。使用时间共聚焦显微镜研究细胞运动。在体内研究中，将U251细胞接种到雌性裸鼠的后腹侧，对肿瘤进行5次2 Gy（10 Gy）的照射。然后使用GE 7T小动物MRI对肿瘤进行成像，以评估T2* MRI的变化，并使用亚铁嗪对不稳定铁进行比色分析。照射后，U251细胞出现了以细胞硬度降低和细胞运动增加为特征的生物力学变化，这与TfR表达增加相对应。FtH过表达完全逆转了照射后增强的细胞运动。U251肿瘤的照射诱导了相同的铁代谢变化。有趣的是，U251肿瘤中不稳定铁的变化与T2弛豫时间的增加相对应，这表明T2成像可能作为评估辐射诱导的铁代谢变化的替代标志物。
