Ihata Tomohiro, Nonoguchi Naosuke, Fujishiro Takahiro, Omura Naoki, Kawabata Shinji, Kajimoto Yoshinaga, Wanibuchi Masahiko
Department of Neurosurgery and Endovascular Neurosurgery, Osaka Medical and Pharmaceutical University, 2-7 Daigaku-Machi, Takatsuki, Osaka 569-8686, Japan.
Department of Neurosurgery and Endovascular Neurosurgery, Osaka Medical and Pharmaceutical University, 2-7 Daigaku-Machi, Takatsuki, Osaka 569-8686, Japan.
Photodiagnosis Photodyn Ther. 2022 Dec;40:103056. doi: 10.1016/j.pdpdt.2022.103056. Epub 2022 Aug 6.
Glioblastoma (GBM) is a high-grade, poor prognosis tumor that is resistant to standard treatment. The presence of a small number of glioma stem cells (GSCs) surviving in the harsh microenvironment is responsible for their refractoriness. This study aimed to investigate the effect of a hypoxic environment on the sensitivity of GSCs to photodynamic therapy with 5-aminolevulinic acid (ALA-PDT).
Six human GSC lines, Mesenchymal types HGG13, HGG30, HGG1123, and Proneural types HGG146, HGG157, HGG528, were divided into two groups: normoxia (O 21%)-cultured cells (Normoxia-GSCs), and hypoxia (O 5%)-cultured cells (Hypoxia-GSCs). To compare the effects of different oxygen partial pressures on photoporphyrin Ⅸ (PpⅨ) biosynthetic activity, PpⅨ biosynthetic enzyme and transporter expression levels were examined by qRT-PCR; the intracellular PpⅨ concentration was determined using flow cytometry. Additionally, the sensitivity of these two groups of cells to ALA-PDT was evaluated in vitro.
Hypoxia-GSCs showed higher mRNA levels of FECH (ferrochelatase), which is required for iron synthesis to convert PpⅨ to heme, compared with Normoxia-GSCs. Flow cytometry revealed that the accumulation of PpⅨ in Hypoxia-GSCs reduced upon incubation with ALA. However, Hypoxia-GSCs showed less reduction in sensitivity to ALA-PDT than Normoxia-GSCs.
Hypoxia-GSCs had lower intracellular PpⅨ accumulation than Normoxia-GSCs due to increased gene expression of FECH, and that their sensitivity to ALA-PDT was reduced less, despite accumulating lower concentrations of PpⅨ. ALA-PDT is a potentially effective therapy for hypoxia-tolerant GSCs that exist in hypoxia at 5% oxygen concentration.
胶质母细胞瘤（GBM）是一种高级别、预后较差且对标准治疗耐药的肿瘤。在恶劣微环境中存活的少量胶质瘤干细胞（GSCs）导致了它们的难治性。本研究旨在探讨缺氧环境对GSCs对5-氨基酮戊酸光动力疗法（ALA-PDT）敏感性的影响。
将六种人GSC系，间充质型HGG13、HGG30、HGG1123，以及神经干细胞型HGG146、HGG157、HGG528，分为两组：常氧（O₂ 21%）培养的细胞（常氧-GSCs）和缺氧（O₂ 5%）培养的细胞（缺氧-GSCs）。为比较不同氧分压对光卟啉Ⅸ（PpⅨ）生物合成活性的影响，通过qRT-PCR检测PpⅨ生物合成酶和转运蛋白的表达水平；使用流式细胞术测定细胞内PpⅨ浓度。此外，在体外评估这两组细胞对ALA-PDT的敏感性。
与常氧-GSCs相比，缺氧-GSCs显示出更高的亚铁螯合酶（FECH）mRNA水平，FECH是铁合成将PpⅨ转化为血红素所必需的。流式细胞术显示，与ALA孵育后，缺氧-GSCs中PpⅨ的积累减少。然而，缺氧-GSCs对ALA-PDT的敏感性降低程度低于常氧-GSCs。
由于FECH基因表达增加，缺氧-GSCs的细胞内PpⅨ积累低于常氧-GSCs，并且尽管PpⅨ浓度较低，但它们对ALA-PDT的敏感性降低程度较小。ALA-PDT对于在5%氧浓度缺氧环境中存在的耐缺氧GSCs是一种潜在有效的治疗方法。
