Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA.
PLoS One. 2013;8(1):e51805. doi: 10.1371/journal.pone.0051805. Epub 2013 Jan 11.
Classical approaches to immunotherapy that show promise in some malignancies have generally been disappointing when applied to high-grade brain tumors such as glioblastoma multiforme (GBM). We recently showed that ex vivo expanded/activated γδ T cells recognize NKG2D ligands expressed on malignant glioma and are cytotoxic to glioma cell lines and primary GBM explants. In addition, γδ T cells extend survival and slow tumor progression when administered to immunodeficient mice with intracranial human glioma xenografts. We now show that temozolomide (TMZ), a principal chemotherapeutic agent used to treat GBM, increases the expression of stress-associated NKG2D ligands on TMZ-resistant glioma cells, potentially rendering them vulnerable to γδ T cell recognition and lysis. TMZ is also highly toxic to γδ T cells, however, and to overcome this cytotoxic effect γδ T cells were genetically modified using a lentiviral vector encoding the DNA repair enzyme O(6)-alkylguanine DNA alkyltransferase (AGT) from the O(6)-methylguanine methyltransferase (MGMT) cDNA, which confers resistance to TMZ. Genetic modification of γδ T cells did not alter their phenotype or their cytotoxicity against GBM target cells. Importantly, gene modified γδ T cells showed greater cytotoxicity to two TMZ resistant GBM cell lines, U373(TMZ-R) and SNB-19(TMZ-R) cells, in the presence of TMZ than unmodified cells, suggesting that TMZ exposed more receptors for γδ T cell-targeted lysis. Therefore, TMZ resistant γδ T cells can be generated without impairing their anti-tumor functions in the presence of high concentrations of TMZ. These results provide a mechanistic basis for combining chemotherapy and γδ T cell-based drug resistant cellular immunotherapy to treat GBM.
经典的免疫疗法方法在某些恶性肿瘤中显示出前景，但在应用于高级别脑肿瘤（如多形性胶质母细胞瘤[GBM]）时通常令人失望。我们最近表明，体外扩增/激活的γδ T 细胞识别恶性神经胶质瘤上表达的 NKG2D 配体，并对神经胶质瘤细胞系和原发性 GBM 外植体具有细胞毒性。此外，当给予颅内人神经胶质瘤异种移植的免疫缺陷小鼠时，γδ T 细胞可延长生存期并减缓肿瘤进展。我们现在表明，替莫唑胺（TMZ）是一种用于治疗 GBM 的主要化疗药物，可增加 TMZ 耐药神经胶质瘤细胞上应激相关 NKG2D 配体的表达，使它们易受 γδ T 细胞识别和裂解。然而，TMZ 对 γδ T 细胞也具有高度毒性，为了克服这种细胞毒性作用，我们使用编码来自 O(6)-甲基鸟嘌呤甲基转移酶（MGMT）cDNA 的 O(6)-烷基鸟嘌呤 DNA 烷基转移酶（AGT）的慢病毒载体对 γδ T 细胞进行了基因修饰，该酶赋予 TMZ 抗性。γδ T 细胞的基因修饰并未改变其表型或对 GBM 靶细胞的细胞毒性。重要的是，在 TMZ 存在下，与未修饰的细胞相比，基因修饰的 γδ T 细胞对两种 TMZ 耐药 GBM 细胞系 U373（TMZ-R）和 SNB-19（TMZ-R）的细胞显示出更强的细胞毒性，这表明 TMZ 暴露了更多的受体供 γδ T 细胞靶向裂解。因此，在存在高浓度 TMZ 的情况下，可以在不损害其抗肿瘤功能的情况下产生 TMZ 耐药的 γδ T 细胞。这些结果为结合化疗和基于 γδ T 细胞的耐药细胞免疫疗法治疗 GBM 提供了机制基础。
