PTEN and neoplasm: In another study, it was shown that exosomal miR-21, secreted by hypoxic mesenchymal stem cells, promotes non-small-cell lung cancer cell mobility, proliferation, and macrophage M2 polarization in vitro and increases tumor growth and intra-tumoral angiogenesis in vivo by inhibiting the expression of PTEN, PDCD4, and RECK (Figure 3) [64].