Abstract
Mesenchymal stromal cells (MSC) exert either tumor-stimulatory or tumor-inhibitory effect. The outcome of the tumor-MSC interaction is dictated by the tumor-specific activating signals. We analyzed the alterations in MSC phenotype in response to stimulation by tumor-secreted paracrine factors. Paracrine factors from human melanoma A375 and glioblastoma 8MGBA cells were used for prolonged culture of MSC to produce derived cells designated DIFF(A)-MSC or DIFF(G)-MSC, respectively. Derived cells were analyzed for the specific surface markers, the expression pattern of MSC markers and fibroblast-specific proteins. Changes in the cell phenotype were evaluated using scratch wound assay and tube formation in vitro; and xenotransplant growth in vivo. Our data show induced expression of vascular endothelial growth factor 2, CD146, fibroblast-specific protein, vimentin and endosialin in DIFF(A)-MSC cells. This indicates their differentiation towards the cells with features of tumor-associated fibroblasts upon stimulation with melanoma-secreted cytokines. Paracrine stimulation in DIFF(G)-MSC led to up-regulation of the genes involved in the MSC differentiation. MSC-specific surface marker characteristics were preserved in derived DIFF(A)-MSC and DIFF(G)-MSC cells. However, we observed increased proportion of CD146 and GD2 (neural ganglioside) positive cells and decreased expression of marker NG2 in the MSC exposed to tumor-conditioned medium. Melanoma-CM increased MSC migration, glioblastoma-CM compromised angiogenic capacity of MSC in vitro and the protumorigenic effect in vivo. Our data directly compare the pleiotropic effects mediated by the malignant cells on the MSC. Secreted paracrine factors from melanoma or glioblastoma differently changed molecular traits in MSC, which explains the dual role of MSC in tumor growth.