Racl＋ cells distributed in accordance with CD 133＋ cells in glioblastomas and the elevated invasiveness of CD 133＋ glioma cells with higher Racl activity

• Published in: 中华医学杂志：英文版 no. 24; pp. 4344 - 4348
• Main Author: ZHANG Bin SUN Jian YU Sheng-ping CHEN Cong LIU Bin LIU Zhi-feng REN Bing-cheng MING Hao-lang YANG Xue-jun
• Format: Journal Article
• Language: English
• Published: 2012
• Subjects: 侵袭; 免疫组织化学染色; 无血清培养基; 母细胞; 细胞分布; 肌动蛋白细胞骨架; 胶质瘤细胞
• ISSN: 0366-6999; 2542-5641

Background Recent studies have suggested that cancer stem cells are one of the major causes for tumor recurrence due to their resistance to radiotherapy and chemotherapy. Although the highly invasive nature of glioblastoma （GBM） cells is also implicated in the failure of current therapies, it is not clear how glioma stem cells （GSCs） are involved in invasiveness. Racl activity is necessary for inducing reorganization of actin cytoskeleton and cell movement. In this study, we aimed to investigate the distribution characteristics of CD133＋ cells and Racl＋ cells in GBM as well as Racl activity in CD133＋ GBM cells, and analyze the migration and invasion potential of these cells. Methods A series of 21 patients with GBM were admitted consecutively and received tumor resection in Tianjin Medical University General Hospital during the first half of the year 2011. Tissue specimens were collected both from the peripheral and the central parts for each tumor under magnetic resonance imaging （MRI） navigation guidance. Immunohistochemical staining was used to detect the CD133＋ cells and Racl＋ cells distribution in GBM specimens. Double-labeling immunofluorescence was further used to analyze CD133 and Racl co-expression and the relationship between CD133＋ cells distribution and Racl expression. Serum-free medium culture and magnetic sorting were used to isolate CD133＋ cells from U87 cell line. Racl activation assay was conducted to assess the activation of Racl in CD133＋ and CD133- U87 cells. The migration and invasive ability of CD133＋ and CD133- U87 cells were determined by cell migration and invasion assays in vitro. Student＇s t-test and one-way analysis of variance （ANOVA） test were used to determine statistical significance in this study. Results In the central parts of GBMs, CD133＋ cells were found to cluster around necrosis and occasionally cluster around the vessels under the microscope by immunohistological staining. In the peripheral parts of the tumors, CD133＋ cells were lined up along the basement membrane of the vessels and myelinated nerve fibers. Racl expression was high and diffused in the central parts of the GBMs, and the Racl＋ cells were distributed basically in accordance with CD133＋ cells both in the central and peripheral parts of GBMs. In double-labeling immunofluorescence, Racl was expressed in （83.14＋4.23）% of CD133＋ cells, and CD133 and Racl co-expressed cells were located around the vessels in GBMs. Significantly higher amounts of Racl-GTP were expressed in the CD133＋ cells （0.378±0.007）, compared to CD133- cells （0.195±0.004） （t=-27.81; P 〈0.05）. CD133＋ cells had stronger ability to migrate （74.34±2.40 vs. 38.72±2.60, t=42.71, P 〈0.005） and invade （52.00±2.28 vs. 31.26±1.82, t=30.76, P 〈0.005）, compared to their counterpart CD133- cells in transwell cell migration/invasion assay. Conclusions These data suggest that CD133＋ GBM cells highly express Racl and have greater potential to migrate and invade through activated Racl-GTP. The accordance of distribution between Racl＋ cells and CD133＋ cells in GBMs implies that Racl might be an inhibited target to prevent invasion and migration and to avoid malignant glioma recurrence