Abstract
Glioblastoma multiforme (GBM) represents the most lethal brain tumour, and these tumours have very limited treatment options. Mesenchymal stem cells (MSC) are considered as candidates for advanced cell therapies, due to their tropism towards GBM, possibly affecting their malignancy, thus also representing a potential therapeutic vector. Therefore, we aimed to compare the effects of bone-marrow-derived versus adipose-tissue-derived MSC (BM-/AT-MSC) on heterogeneous populations of tumour cells. This cells’ interplay was addressed by the in-vitro two-dimensional (monolayer) and three-dimensional (spheroid) co-culture models, using U87 and U373 GBM cell lines, expressing genotypically different mesenchymal transcriptome profiles. U87 cell low mesenchymal profile expressed high levels of kinin receptor 1 (B1R) and their invasion was greatly enhanced by the B1R agonist des-Arg9-bradykinin upon BM-MSC co-culturing in 3D co-cultures. This correlated to significantly higher cell-cell interactions in U87/BM-MSC mixed spheroids. This was not observed with the U373 cells and not in AT-MSC co-cultures. Altogether, these data support the on-going exploration of B1R as target for adjuvant approach in GBM therapy. Secondly, the results emphasize the need for further careful exploration of the selectivity regarding the origin of MSC as potential candidates for cell therapies, particular in cancer, where they may adversely affect heterogeneous tumour cell populations.
Highlights
We have previously demonstrated that in-vitro cross-talk between bone-marrow-derived Mesenchymal stem cells (MSC) (BM-MSC) and U87 Glioblastoma multiforme (GBM) cells in an ‘indirect’ co-culture model resulted in their altered expression of over 500 and 300 genes, respectively[9]
The proliferation rates of the U87dsRed and U373eGFP GBM cells and bone-marrow-derived MSC (BM-MSC) as mono-spheroids and mixed spheroids were assessed for their viability using the 3-(4,5-dimethylthiazol-2-yl)-5(3-carboxymethonyp henol)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) as say in terms of the metabolic activity of the cells (Fig. 1B), and for their population doubling times in terms of automated cell counting (Fig. 1C)
As BM-MSC proliferation was slower compared to these GBM cells, as shown by the lower metabolic activity of the BM-MSC versus GBM mono-spheroids, we can conclude that in our experimental condition the metabolically more active and proliferating GBM cells accounted for the increased metabolic activity of these GBM/BM-MSC mixed spheroids (Fig. 1B)
Summary
We have previously demonstrated that in-vitro cross-talk between bone-marrow-derived MSC (BM-MSC) and U87 GBM cells in an ‘indirect’ co-culture model (i.e., cells sharing medium, without direct cell-cell contact) resulted in their altered expression of over 500 and 300 genes, respectively[9]. The B2R is constitutively expressed and has high affinity for the binding of BK and kallidin peptides; in contrast, B1R is an inducible receptor with affinity for DBK and des-Arg9-kallidin In cancer, these kinin receptors are involved in cell proliferation, chemotaxis and invasion[17], such as in breast carcinoma[18] and glioma cells[19]. Pillat et al.[21] previously showed that both B1R and B2R are expressed at the mRNA and protein levels in U87 cells and in BM-MSC in vitro They demonstrated that in indirect and direct co-cultures of U87 cells with BM-MSC, B1R gene and protein expression increased in U87 cells, which was correlated with their enhanced invasiveness via induction of metalloproteases. The present study has important implications for potential MSC therapies for GBM, providing mechanisms for their their interactions with tumour cells[24]
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