REPOSITORY > RESULTS

Abstract

Glioblastoma multiforme (GBM) represents the most lethal brain tumor with very limited treatment options. Mesenchymal stem cells (MSCs) are considered as candidates for advanced cell therapy, due to their tropism towards GBM, either directly affecting their
malignancy or acting as a potential therapeutic vector. Here, we aimed to compare the
effects of bone marrow (BM) and adipose tissue (AT) MSC on two different tumor cells lines of GBM population. The interplay of these cells was addressed with U87 and U373 GBM cell lines by in vitro two-dimensional (monolayer) and three-dimensional (spheroid)
co-culture models. Indirect co-cultures, where the cells interacted by paracrine mechanism, as well as direct interactions in co-cultures promoted an increase in kinin-B1(B1R) and kinin-B2 (B2R) receptor expression levels in U87 cells, which was not observed in MSCs. The functionality of B1 and B2R was monitored by stimulation of intracellular calcium fluxes upon their respective agonists des-arg9-bradykinin (DBK) and bradykinin (BK), respectively. Moreover, BK induced a feedback control on kinin-receptor expression in
direct and indirect co-cultures, as the treatment with BK increased expression levels of both receptors in U87 cells. This suggests that BK functions in the flow of information between GBM-MSC, being important for tumor progression. U87 cell migration and invasion in 3D co-cultures with BM-MSCs were greatly enhanced by kinin receptor agonists and blocked antagonists of these receptors. Enhanced migration and invasion correlated with significantly higher cell-cell interactions, such as more frequent heterotypic cell fusions and even cell cannibalism, as well as vesicle transfer between U87 and BM-MSC cells in direct co-cultures. These cell-cell interactions were also reduced after B1R antagonism. Further, CD105 and CD90 MSC phenotype biomarker acquisition occurred in U87 cells after these had been co-cultured with MSCs. BK promoted upregulation of epithelial-tomesenchymal transition (EMT) gene expression together with F-actin expression in U87
cells which is associated with cell-cell interaction and invasion. In conclusion, GBM-MSC interactions promote tumor cell invasion, migration and EMT by inducing kinin receptor
expression. Supposedly, kinin receptor activation favors these events by increasing tumor aggressiveness and, thus, may provide a novel therapeutic target.