Fig. 6.

Conditioned medium from mesenchymal stem cells (MSCs) exposed to tumour cell–derived extracellular vesicles (EVs) enhances tumour cell proliferation. (a) KMBC cells were incubated with conditioned medium obtained from MSCs cultured in the presence or absence of KMBC-EVs. Cell proliferation was assessed using an MTS assay. Compared to controls, conditioned medium (CM) from MSCs exposed to KMBC-EVs increased KMBC cell proliferation. *p<0.001 vs. CM (control), **p<0.0001 vs. CM (control), ***p<0.05 vs. CM (MSCs). (b) Cell proliferation was assessed after 72 hours using MTS assay. Anti-IL-6R antibody, but not anti-CXCL-1 antibody, blocked enhanced KMBC cell proliferation in response to conditioned medium from MSCs exposed to tumour-derived EVs. Bars express the mean value±SEM of 3 separate studies. *p<0.05, **p<0.01, ***p<0.001. (c) Immunoblot analyses of p-STAT3/STAT3 protein expression in KMBC cells. Anti-IL-6R antibody blocked enhanced STAT3 activation in response to CM from MSCs exposed to tumour-derived EVs. Bars represent quantitative densitometric data from 3 replicates. (d) KMBC cell migration was assessed using a transwell migration assay. KMBC cells were treated with CM from MSCs and MSCs exposed to KMBC-EVs. Representative images of migrated cells and quantitative data representing the mean (±SEM) number of migrated cells from 3 separate studies. Tumour cell migration was increased by MSC-CM but was not further enhanced by prior exposure of MSCs to KMBC-EVs.