MSC-Derived Extracellular Vesicles in Tumors and Therapy

Exosomes derived from mesenchymal stroma-/stem-like cells (MSCs) as part of extracellular vesicles are considered cell-free biocompatible nanovesicles that promote repair activities of damaged tissues or organs by exhibiting low immunogenic and cytotoxic effects. Contributions to regenerative activities include wound healing, maintenance of stem cell niches, beneficial regenerative effects in various diseases, and reduction of senescence. However, the mode of action in MSC-derived exosomes strongly depends on the biological content like different regulatory microRNAs that are determined by the tissue origin of MSCs. In tumors, MSCs use indirect and direct pathways in a communication network to interact with cancer cells. This leads to mutual functional changes with the acquisition of an aberrant tumor-associated MSC phenotype accompanied by altered cargo in the exosomes. Consequently, MSC-derived exosomes either from normal tissue-originating MSCs or from aberrant tumor-associated MSCs can confer different actions on tumor development. These processes exhibiting tumor-inhibitory and tumor-supportive effects with a focus on exosome microRNA content will be discriminated and discussed within this review.