Cellular and Molecular Neuro-oncology Research Group, Institute of Biomedical and Biomolecular Sciences, School of Pharmacy and Biomedical Sciences, University of Portsmouth, Portsmouth, United Kingdom.
PLoS One. 2012;7(2):e30691. doi: 10.1371/journal.pone.0030691. Epub 2012 Feb 17.
CD44 has long been associated with glioma invasion while, more recently, CD155 has been implicated in playing a similar role. Notably, these two receptors have been shown closely positioned on monocytes.
In this study, an up-regulation of CD44 and CD155 was demonstrated in established and early-passage cultures of glioblastoma. Total internal reflected fluorescence (TIRF) microscopy revealed close proximity of CD44 and CD155. CD44 antibody blocking and gene silencing (via siRNA) resulted in greater inhibition of invasion than that for CD155. Combined interference resulted in 86% inhibition of invasion, although in these investigations no obvious evidence of synergy between CD44 and CD155 in curbing invasion was shown. Both siRNA-CD44 and siRNA-CD155 treated cells lacked processes and were rounder, while live cell imaging showed reduced motility rate compared to wild type cells. Adhesion assay demonstrated that wild type cells adhered most efficiently to laminin, whereas siRNA-treated cells (p<0.0001 for both CD44 and CD155 expression) showed decreased adhesion on several ECMs investigated. BrdU assay showed a higher proliferation of siRNA-CD44 and siRNA-CD155 cells, inversely correlated with reduced invasion. Confocal microscopy revealed overlapping of CD155 and integrins (β(1), α(v)β(1) and α(v)β(3)) on glioblastoma cell processes whereas siRNA-transfected cells showed consequent reduction in integrin expression with no specific staining patterns. Reduced expression of Rho GTPases, Cdc42, Rac1/2/3, RhoA and RhoB, was seen in siRNA-CD44 and siRNA-CD155 cells. In contrast to CD44-knockdown and 'double'-knockdown cells, no obvious decrease in RhoC expression was observed in CD155-knockdown cells.
This investigation has enhanced our understanding of cell invasion and confirmed CD44 to play a more significant role in this biological process than CD155. Joint CD44/CD155 approaches may, however, merit further study in therapeutic targeting of infiltrating glioma cells.
CD44 长期以来一直与神经胶质瘤的侵袭有关，而最近 CD155 也被认为在发挥类似作用。值得注意的是，这两个受体已被证明在单核细胞上紧密定位。
在这项研究中，在已建立的和早期传代的神经胶质瘤培养物中证明了 CD44 和 CD155 的上调。全内反射荧光（TIRF）显微镜显示 CD44 和 CD155 非常接近。CD44 抗体阻断和基因沉默（通过 siRNA）导致侵袭抑制作用大于 CD155。联合干扰导致侵袭抑制率达到 86%，尽管在这些研究中，没有明显证据表明 CD44 和 CD155 在抑制侵袭方面具有协同作用。siRNA-CD44 和 siRNA-CD155 处理的细胞缺乏突起且呈圆形，而活细胞成像显示与野生型细胞相比，迁移率降低。黏附实验表明，野生型细胞最有效地黏附到层粘连蛋白上，而 siRNA 处理的细胞（CD44 和 CD155 表达均<0.0001）在几种研究的 ECM 上显示出较低的黏附能力。BrdU 测定显示 siRNA-CD44 和 siRNA-CD155 细胞的增殖率较高，与侵袭减少呈反比。共聚焦显微镜显示 CD155 与整合素（β(1)、α(v)β(1)和 α(v)β(3)）在神经胶质瘤细胞突起上重叠，而转染 siRNA 的细胞表现出整合素表达的相应减少，没有特定的染色模式。siRNA-CD44 和 siRNA-CD155 细胞中 Rho GTPases、Cdc42、Rac1/2/3、RhoA 和 RhoB 的表达减少。与 CD44 敲低和“双重”敲低细胞相比，在 CD155 敲低细胞中没有观察到 RhoC 表达的明显减少。
本研究增强了我们对细胞侵袭的理解，并证实 CD44 在这一生物学过程中比 CD155 发挥更重要的作用。然而，CD44/CD155 联合方法可能值得进一步研究，以作为侵袭性神经胶质瘤细胞治疗的靶点。
