Glioblastoma cell invasiveness and epithelial-to-mesenchymal transitioning are modulated by kinin receptors

Glioblastoma (GB) is the most aggressive primary tumor of central nervous system, where no efficient therapy has been found so far. This is due to high intra- and inter- tumor heterogeneity, fast invasion and the therapy-resistant subpopulation of GB stem cells and their plasticity. Tumor heterogeneity involves interactions among cancer cells and stromal cells, such as mesenchymal stem cells (MSCs), that are recruited into the tumor microenvironment and migrate to the tumor site. Here, we characterized the impact of kinin receptors on the interaction of MSCs with GB cells which is further enhanced by kinin receptor agonists. Interactions between GB cells and MSCs were studied in two- and three-dimensional co-cultures. Kinin receptor activity was modulated by selective agonists and antagonists to evaluate their influence on cell viability, cell-cell interactions, GB U87 cell invasiveness, and phenotype alterations. Tumor cell invasion was enhanced by the kinin-B2 receptor agonist bradykinin, while it was blocked by B2 receptor antagonists applied in U87 cells monoculture and in co-culture with MSCs. Kinin receptor inhibition correlated with enhanced direct U87/MSC interactions, such as heterotypic fusion, vesicle transfer and entosis. Furthermore, kinin receptor modulation influenced expression of F-actin expression and genes associated with epithelial-to-mesenchymal transition in U87 cells upon U87/MSCs co-cultures. Our data support ongoing investigations of kinin receptor inhibition as an adjuvant approach in GB therapy. MSC impacts on cancer progression need further investigation, as they may have a synergistic effect with kininergic receptor activation.