Institute of Carcinogenesis, NN Blokhin Cancer Research Center of the Russian Academy of Medical Sciences, Moscow, Russia.
PLoS One. 2009 Nov 30;4(11):e8027. doi: 10.1371/journal.pone.0008027.
E-cadherin-mediated cell-cell adhesion, which is essential for the maintenance of the architecture and integrity of epithelial tissues, is often lost during carcinoma progression. To better understand the nature of alterations of cell-cell interactions at the early stages of neoplastic evolution of epithelial cells, we examined the line of nontransformed IAR-2 epithelial cells and their descendants, lines of IAR-6-1 epithelial cells transformed with dimethylnitrosamine and IAR1170 cells transformed with N-RasG12D. IAR-6-1 and IAR1170 cells retained E-cadherin, displayed discoid or polygonal morphology, and formed monolayers similar to IAR-2 monolayer. Fluorescence staining, however, showed that in IAR1170 and IAR-6-1 cells the marginal actin bundle, which is typical of nontransformed IAR-2 cells, disappeared, and the continuous adhesion belt (tangential adherens junctions (AJs)) was replaced by radially oriented E-cadherin-based AJs. Time-lapse imaging of IAR-6-1 cells stably transfected with GFP-E-cadherin revealed that AJs in transformed cells are very dynamic and unstable. The regulation of AJ assembly by Rho family small GTPases was different in nontransformed and in transformed IAR epithelial cells. As our experiments with the ROCK inhibitor Y-27632 and the myosin II inhibitor blebbistatin have shown, the formation and maintenance of radial AJs critically depend on myosin II-mediated contractility. Using the RNAi technique for the depletion of mDia1 and loading cells with N17Rac, we established that mDia1 and Rac are involved in the assembly of tangential AJs in nontransformed epithelial cells but not in radial AJs in transformed cells. Neoplastic transformation changed cell-cell interactions, preventing contact paralysis after the establishment of cell-cell contact and promoting dynamic cell-cell adhesion and motile behavior of cells. It is suggested that the disappearance of the marginal actin bundle and rearrangements of AJs may change the adhesive function of E-cadherin and play an active role in migratory activity of carcinoma cells.
E-钙黏蛋白介导的细胞-细胞黏附对于维持上皮组织的结构和完整性至关重要，而这种黏附在癌进展过程中常常丢失。为了更好地理解上皮细胞癌变早期细胞-细胞相互作用改变的本质，我们研究了非转化的 IAR-2 上皮细胞及其衍生的、用二甲基亚硝胺转化的 IAR-6-1 上皮细胞系和用 N-RasG12D 转化的 IAR1170 细胞系。IAR-6-1 和 IAR1170 细胞保留了 E-钙黏蛋白，呈盘状或多角形形态，并形成类似于 IAR-2 单层的单层。然而，荧光染色显示，在 IAR1170 和 IAR-6-1 细胞中，典型的非转化 IAR-2 细胞的边缘肌动球蛋白束消失，连续的黏附带（切向黏附连接（AJ））被放射状排列的 E-钙黏蛋白基 AJ 取代。用 GFP-E-钙黏蛋白稳定转染的 IAR-6-1 细胞的延时成像显示，转化细胞中的 AJ 非常动态和不稳定。Rho 家族小 GTPase 对 AJ 组装的调节在非转化和转化的 IAR 上皮细胞中不同。正如我们用 ROCK 抑制剂 Y-27632 和肌球蛋白 II 抑制剂 blebbistatin 的实验所示，放射状 AJ 的形成和维持严重依赖于肌球蛋白 II 介导的收缩性。通过 RNAi 技术耗尽 mDia1 并将 N17Rac 加载到细胞中，我们证实 mDia1 和 Rac 参与了非转化上皮细胞中切向 AJ 的组装，但不参与转化细胞中放射状 AJ 的组装。肿瘤转化改变了细胞-细胞相互作用，阻止了细胞-细胞接触建立后的接触麻痹，并促进了细胞的动态细胞-黏附和迁移行为。这表明，边缘肌动球蛋白束的消失和 AJ 的重排可能改变 E-钙黏蛋白的黏附功能，并在上皮癌细胞的迁移活性中发挥积极作用。
