gms | German Medical Science

Objective: Cadherins are key components of the adherens junction complexes. Thus, they are responsible for cell-cell adhesion as well as cell motility. Changes in the cadherin expression profile, so called cadherin switching, are essential mechanisms in tissue morphogenesis but can also be involved in tumor progression. Especially in epithelial carcinomas, loss of E-cadherin expression or function contributes to diminished cell polarity and promotes epithelial-mesenchymal transition (EMT). Finally, during tumor progression this alteration leads to a more invasive phenotype which is accompanied with a worse prognosis for patients. Interestingly, some studies revealed expression of E-cadherin in a rare subset of GBM cells which was correlated with a more unfavorable clinical outcome.

Method: We investigated the impact of the level of E-cadherin expression on cell polarity, migration, and spheroid formation in tumor glial cells. Retroviral shRNA-vectors were used to stably knockdown E-cadherin in U343-MG cells. Subsequently, the resulting phenotype was analyzed by Western Blot, BrdU (5-bromo-2'-deoxyuridine)-incorporation, clonogenic survival assay, wound healing assay, migration/invasion assay, and spheroid formation experiments.

Results: Our findings indicate that the knockdown of E-cadherin significantly decreased the proliferation capacity of U343-MG glioma cells caused by reduced levels of cyclinD1. The classical EMT-phenotype, characterized by an upregulation of N-cadherin, was not observed. Moreover, clonogenic survival assay revealed significant lower amounts of colonies with a smaller size after knockdown of E-cadherin when compared to control cells. In wound healing and invasion assays E-cadherin depleted glioma cells displayed a diminished migration potential. However, two-dimensional cultivation did not show distinct morphological changes after E-cadherin knockdown when cells closely attached to plastic. When U343-MG E-cadherin knockdown cells were cultivated on agarose, their ability to form compact three-dimensional spheroids was clearly impaired in comparison to appropriate control cells.

Conclusions: Unlike many epithelial cancers, E-cadherin depleted U343-MG cells did not show a typical EMT-transition that is normally accompanied with a more aggressive tumor phenotype. Our findings suggest a critical role of E-cadherin in migration and survival in a small subset of GBM.