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A recent study has discovered that mesenchymal stem cells (MSCs) are recruited into tumors and MSC-derived exosomes in a novel mechanism of cell-to-cell communication in human cancers. Here, in this study, we explore the impact of the microRNA-208a (miR-208a)-enriched exosomes derived from bone marrow-derived mesench- ymal stem cells (BMSCs) on osteosarcoma cells. Human osteosarcoma cells MG-63and Saos-2 were exposed to BMSCs-derived exosomes treated with either miR-208a mimic or inhibitor. The MTT assay, transwell migration assay, and soft agar colony formation assay were used to evaluate the viability, migration, and clonogenicity of osteosarcoma cells. Bioinformatics analysis and dual-luciferase reporter gene assays validated the targeted relationship between miR-208a and PDCD4. Western blot assay was used to detect the expression of PDCD4 and related proteins in the ERK1/2 pathway in osteosarcoma cells. BMSCs communicated with osteosarcoma cells via exosomes. Ectopic expression of miR-208a was shown to increase the viability, migration, and clonogenicity of osteosarcoma cells. Analysis of the exosomal content identified miR-208a as a mediator of the exosomal effects on osteosarcoma cells in part via downregulation of PDCD4 and activating the ERK1/2 pathway. In summary, our study illuminates that BMSC-derived exosomal miR-208a enhances the progression of osteosarcoma. K E Y W O R D Sbone marrow-derived mesenchymal stem cells, exosome, microRNA-208a, osteosarcoma, PDCD4

The effects of nuclear superfluidity on antimagnetic rotation bands in 105 Cd and 106 Cd are investigated by the cranked shell model with the pairing correlations and the blocking effects treated by a particle-number conserving method. The experimental moments of inertia and the reduced B(E2) transition values are excellently reproduced. The nuclear superfluidity is essential to reproduce the experimental moments of inertia. The two-shears-like mechanism for the antimagnetic rotation is investigated by examining the shears angle, i.e., the closing of the two proton hole angular momenta, and its sensitive dependence on the nuclear superfluidity is revealed.

Dissolution of metal oxides is fundamentally important for understanding mineral evolution and micromachining oxide functional materials. In general, dissolution of metal oxides is a slow and inefficient chemical reaction. Here, by introducing oxygen deficiencies to modify the surface chemistry of oxides, we can boost the dissolution kinetics of metal oxides in water, as in situ demonstrated in a liquid environmental transmission electron microscope (LETEM). The dissolution rate constant significantly increases by 16-19 orders of magnitude, equivalent to a reduction of 0.97-1.11 eV in activation energy, as compared with the normal dissolution in acid. It is evidenced from the high-resolution TEM imaging, electron energy loss spectra, and first-principle calculations where the dissolution route of metal oxides is dynamically changed by local interoperability between altered water chemistry and surface oxygen deficiencies via electron radiolysis. This discovery inspires the development of a highly efficient electron lithography method for metal oxide films in ecofriendly water, which offers an advanced technique for nanodevice fabrication.

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