Soroceanu L, Gillespie Y, Khazaeli M B, Sontheimer H
Department of Neurobiology, University of Alabama at Birmingham, 35294, USA.
Cancer Res. 1998 Nov 1;58(21):4871-9.
Gliomas are primary brain tumors that arise from differentiated glial cells through a poorly understood malignant transformation. Although glioma cells retain some genetic and antigenic features common to glial cells, they show a remarkable degree of antigenic heterogeneity and variable mutations in their genome. Glioma cells have recently been shown to express a glioma-specific chloride ion channel (GCC) that is sensitive to chlorotoxin (CTX), a small peptide purified from Leiurus quinquestriatus scorpion venom [N. Ullrich et al, Neuroreport, 7: 1020-1024, 1996; and N. Ullrich and H. Sontheimer, Am. J. Physiol. (Cell Physiol.), 270: C1511-C1521, 1996]. Using native and recombinant 125I-labeled CTX, we show that toxin binding to glioma cells is specific and involves high affinity [dissociation constant (Kd)=4.2 nM] and low affinity (Kd=660 nml) binding sites. In radioreceptor assays, 125I-labeled CTX binds to a protein with Mr=72,000, presumably GCC or a receptor that modulates GCC activity. In vivo targeting and biodistribution experiments were obtained using 125I- and (131)I-labeled CTX injected into severe combined immunodeficient mice bearing xenografted gliomas. CTX selectively accumulated in the brain of tumor-bearing mice with calculated brain: muscle ratios of 36.4% of injected dose/g (ID/g), as compared to 12.4% ID/g in control animals. In the tumor-bearing severe combined immunodeficient mice, the vast majority of the brain-associated radioactivity was localized within the tumor (tumor:muscle ratio, 39.13% ID/g; contralateral brain:muscle ratio, 6.68%ID/g). Moreover, (131)I-labeled CTX distribution, visualized through in vivo imaging by gamma ray camera scans, demonstrates specific and persistent intratumoral localization of the radioactive ligand. Immunohistochemical studies using biotinylated and fluorescently tagged CTX show highly selective staining of glioma cells in vitro, in situ, and in sections of patient biopsies. Comparison tissues including normal human brain, kidney, and colon were consistently negative for CTX immunostaining. These data suggest that CTX and CTX-conjugated molecules may serve as glioma-specific markers with diagnostic and therapeutic potential.
胶质瘤是起源于分化的神经胶质细胞的原发性脑肿瘤，其恶性转化机制尚不清楚。尽管胶质瘤细胞保留了一些神经胶质细胞共有的遗传和抗原特征，但它们在基因组中表现出显著程度的抗原异质性和可变突变。最近发现胶质瘤细胞表达一种对氯毒素（CTX）敏感的胶质瘤特异性氯离子通道（GCC），氯毒素是一种从以色列金蝎毒液中纯化的小肽[N. Ullrich等人，《神经报告》，7: 1020 - 1024，1996；N. Ullrich和H. Sontheimer，《美国生理学杂志》（细胞生理学），270: C1511 - C1521，1996]。使用天然和重组的125I标记的CTX，我们发现毒素与胶质瘤细胞的结合是特异性的，涉及高亲和力[解离常数（Kd）=4.2 nM]和低亲和力（Kd = 660 nM）结合位点。在放射受体分析中，125I标记的CTX与一种分子量为72,000的蛋白质结合，推测该蛋白质为GCC或调节GCC活性的受体。使用注射到携带异种移植胶质瘤的严重联合免疫缺陷小鼠体内的125I和131I标记的CTX进行体内靶向和生物分布实验。CTX选择性地积聚在荷瘤小鼠的脑中，计算得出脑与肌肉的比值为注射剂量的36.4%/克（ID/g），而对照动物为12.4% ID/g。在荷瘤严重联合免疫缺陷小鼠中，绝大多数与脑相关的放射性物质位于肿瘤内（肿瘤与肌肉的比值为39.13% ID/g；对侧脑与肌肉的比值为6.68% ID/g）。此外，通过γ射线相机扫描进行体内成像可视化的131I标记的CTX分布，显示放射性配体在肿瘤内有特异性和持续性定位。使用生物素化和荧光标记的CTX进行的免疫组织化学研究表明，在体外、原位和患者活检切片中，胶质瘤细胞有高度选择性染色。包括正常人脑、肾和结肠在内的对照组织对CTX免疫染色始终为阴性。这些数据表明，CTX和CTX偶联分子可能作为具有诊断和治疗潜力的胶质瘤特异性标志物。
