Department of Stem Cell Biology & Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Ave., NE3-301, Cleveland, OH 44195, USA.
Cancer Res. 2013 Aug 1;73(15):4923-36. doi: 10.1158/0008-5472.CAN-12-4556. Epub 2013 Jun 24.
Glioblastomas display cellular hierarchies with self-renewing tumor-initiating cells (TIC), also known as cancer stem cells, at the apex. Although the TIC hypothesis remains controversial and the functional assays to define the TIC phenotype are evolving, we and others have shown that TICs may contribute to therapeutic resistance, tumor spread, and angiogenesis. The identification of TICs has been informed by the use of markers characterized in normal stem cells, but this approach has an inherent limitation to selectively identify TICs. To develop reagents that enrich TICs but not matched non-TICs or tissue-specific stem cells, we adopted Cell-Systematic Evolution of Ligands by Exponential Enrichment (Cell-SELEX) to identify glioblastoma TIC-specific nucleic acid probes-aptamers-that specifically bind TICs. In this study, using Cell-SELEX with positive selection for TICs and negative selection for non-TICs and human neural progenitor cells, we identified TIC aptamers that specifically bind to TICs with excellent dissociation constants (Kd). These aptamers select and internalize into glioblastoma cells that self-renew, proliferate, and initiate tumors. As aptamers can be modified to deliver payloads, aptamers may represent novel agents that could selectively target or facilitate imaging of TICs.
胶质母细胞瘤表现出细胞层次结构，顶端是具有自我更新能力的肿瘤起始细胞（TIC），也称为癌症干细胞。尽管 TIC 假说仍然存在争议，并且定义 TIC 表型的功能检测方法也在不断发展，但我们和其他人已经表明，TIC 可能有助于治疗抵抗、肿瘤扩散和血管生成。TIC 的鉴定得益于在正常干细胞中表征的标记物的使用，但这种方法具有内在的局限性，无法选择性地识别 TIC。为了开发能够富集 TIC 而不是匹配的非 TIC 或组织特异性干细胞的试剂，我们采用细胞系统进化的配体通过指数富集（Cell-SELEX）来鉴定胶质母细胞瘤 TIC 特异性核酸探针-适体-可特异性结合 TIC。在这项研究中，我们使用 Cell-SELEX 对 TIC 进行正选择，对非 TIC 和人神经祖细胞进行负选择，鉴定了 TIC 适体，其与 TIC 具有极好的解离常数（Kd）特异性结合。这些适体选择并内化到自我更新、增殖和引发肿瘤的胶质母细胞瘤细胞中。由于适体可以被修饰以传递有效载荷，因此适体可能代表新的药物，这些药物可以选择性地靶向或促进 TIC 的成像。
