Department of Radiation Oncology, University of Michigan Medical School and Rogel Cancer Center, Ann Arbor, Michigan.
Department of Medicinal Chemistry, College of Pharmacy, and Rogel Cancer Center, University of Michigan, Ann Arbor, Michigan.
Cancer Res. 2019 Jun 1;79(11):2923-2932. doi: 10.1158/0008-5472.CAN-18-2540. Epub 2019 Apr 17.
Patients with glioblastoma multiforme (GBM) survive on average 12 to 14 months after diagnosis despite surgical resection followed by radiotheraphy and temozolomide therapy. Intrinsic or acquired resistance to chemo- and radiotherapy is common and contributes to a high rate of recurrence. To investigate the therapeutic potential of protein disulfide isomerase (PDI) as a target to overcome resistance to chemoradiation, we developed a GBM tumor model wherein conditional genetic ablation of prolyl 4-hydroxylase subunit beta (P4HB), the gene that encodes PDI, can be accomplished. Loss of PDI expression induced the unfolded protein response (UPR) and decreased cell survival in two independent GBM models. Nascent RNA Bru-seq analysis of PDI-depleted cells revealed a decrease in transcription of genes involved in DNA repair and cell-cycle regulation. Activation of the UPR also led to a robust decrease in RAD51 protein expression as a result of its ubiquitination-mediated proteosomal degradation. Clonogenic survival assays demonstrated enhanced killing of GBM cells in response to a combination of PDI knockdown and ionizing radiation (IR) compared with either modality alone, which correlated with a decreased capacity to repair IR-induced DNA damage. Synergistic tumor control was also observed with the combination of PDI inhibition and IR in a mouse xenograft model compared with either single agent alone. These findings provide a strong rationale for the development of PDI inhibitors and their use in combination with DNA damage-inducing, standard-of-care therapies such as IR. SIGNIFICANCE: These findings identify PDIA1 as a therapeutic target in GBM by demonstrating efficacy of its inhibition in combination with radiotherapy through a novel mechanism involving downregulation of DNA repair genes. http://cancerres.aacrjournals.org/content/canres/79/11/2923/F1.large.jpg.
尽管在手术切除后进行放射治疗和替莫唑胺治疗，多形性胶质母细胞瘤（GBM）患者的平均存活时间仍为 12 至 14 个月。对化疗和放疗的内在或获得性耐药很常见，这也是导致高复发率的原因之一。为了研究蛋白二硫键异构酶（PDI）作为克服化疗和放疗耐药的靶点的治疗潜力，我们开发了一种 GBM 肿瘤模型，其中脯氨酰 4-羟化酶亚基β（P4HB）的条件性基因缺失（该基因编码 PDI）可以完成。PDI 表达的缺失诱导未折叠蛋白反应（UPR）并降低两种独立的 GBM 模型中的细胞存活率。PDI 耗尽细胞的新生 RNA Bru-seq 分析显示，参与 DNA 修复和细胞周期调节的基因转录减少。UPR 的激活还导致 RAD51 蛋白表达的大量减少，这是由于其泛素化介导的蛋白酶体降解。集落形成存活测定表明，与单独使用任何一种方法相比，PDI 敲低和电离辐射（IR）的组合对 GBM 细胞的杀伤作用增强，这与修复 IR 诱导的 DNA 损伤的能力降低有关。与单独使用任何一种药物相比，在小鼠异种移植模型中，PDI 抑制与 IR 的联合也观察到协同的肿瘤控制。这些发现为开发 PDI 抑制剂及其与包括 IR 在内的标准护理治疗相结合提供了强有力的理由。意义：这些发现通过证明其抑制与放射治疗联合使用的疗效，通过涉及下调 DNA 修复基因的新机制，确定 PDIA1 是 GBM 的治疗靶点。
