Human mesenchymal stroma/stem-like cell-derived taxol-loaded EVs/exosomes transfer anti-tumor microRNA signatures and express enhanced SDF-1-mediated tumor tropism.

BACKGROUND

The release of extracellular vesicles (EVs) including exosomes from human mesenchymal stroma/stem-like cells (MSC) represents valuable cell-free carriers for the delivery of regenerative and medicinal compounds.

METHODS

EVs/exosomes were isolated by differential centrifugation from four individual MSC as controls and after treatment with a sub-lethal concentration of 10 mM taxol for 24 h, respectively. The isolated EVs/exosomes were characterized and quantified by nano-tracking-analysis and by Western blots. MicroRNAs (miRs) were isolated from the different EVs/exosome populations and expression levels were quantified by qPCR using 1246 miR templates. Cytotoxic effects of the different MSC-derived taxol-loaded EVs/exosomes were determined in five different GFP-transduced cancer cell lines and quantified by a fluoroscan assay with a GFP-detecting fluorimeter. The presence of stroma cell-derived factor 1 (SDF-1) in MSC-derived EVs/exosomes and its enhanced expression in the vesicles after taxol treatment of MSC was quantified by a specific ELISA.

RESULTS

EVs/exosomes isolated from four individual taxol-treated MSC displayed a larger size and higher yields as the control EVs/exosomes and were used as anti-tumor therapeutic vehicles. Application of each of the four MSC-derived taxol-loaded EVs/exosome populations revealed significant cytotoxic effects in cell lines of five different tumor entities (carcinomas of lung, breast, ovar, colon, astrocytoma) in a concentration-dependent manner. Expression analysis of 1246 miRs in these taxol-loaded EVs/exosomes as compared to the corresponding MSC-derived control EVs/exosomes unraveled a taxol-mediated up-regulation of 11 miRs with predominantly anti-tumorigenic properties. Moreover, various constitutively expressed protein levels were unanimously altered in the MSC cultures. Taxol treatment of the different MSC revealed an up-regulation of tetraspanins and a 2.2-fold to 5.4-fold increased expression of SDF-1 among others. Treatment of cancer cells with MSC-derived taxol-loaded EVs/exosomes in the presence of a neutralizing SDF-1 antibody significantly abolished the cytotoxic effects between 20.3% and 27%.

CONCLUSIONS

These findings suggested a taxol-mediated increase of anti-cancer properties in MSC that enhance the tropism of derived EVs/exosomes to tumors, thereby specifically focusing the therapeutic effects of the delivered products.