Bone marrow-mesenchymal stem cell-derived extracellular vesicles affect proliferation and apoptosis of leukemia cells in vitro.

Mesenchymal stem cells (MSCs) have been proposed to have potential for tissue engineering and cell therapy due to their multilineage differentiation potential and ability to secrete numerous paracrine factors, including extracellular vesicles (EVs). Increasing evidence has demonstrated that MSC-derived EVs (MSC-EVs) are able to induce the repair of tissue damage and regulate the immune system. However, their role in cancer development is still unclear. Reports have suggested that whether MSC-EVs have an inhibitory or promoting effect on cancer is dependent on the type of cancer. In this study, the role of MSC-EVs in the regulation of leukemic cell growth in vitro was investigated. The EVs were collected from conditioned media of MSCs by ultrafiltration using a 10 kDa molecular weight cutoff (MWCO) filter. The isolated MSC-EVs were comprised of microvesicles and exosomes, as examined by the size of vesicles and exosomal proteins, CD81 and flotillin-1. Cell proliferation, cell cycle status, apoptosis, and gene expression were examined in the leukemic cell lines NB4 and K562 after treatment with MSC-EVs. Suppression of cell proliferation and induction of apoptosis was observed. Gene expression analysis revealed differential expression of apoptotic-related genes in NB4 and K562. MSC-EVs increased the expression of BID and BAX and decreased expression of BCL2, indicating the induction of intrinsic apoptosis in NB4. In contrast, MSC-EVs increased the expression of the death receptor gene TRAILR2 and cell cycle regulator genes P21 and CCNE2 in K562. In conclusion, MSC-EVs partially induce leukemic cell apoptosis, and thus may have potential for the development of supportive therapies for leukemia.