Figure 1

Tumour cell-derived exosomes endowed BM-MSCs with the ability to promote tumour growth in vivo. (a) A representative electron microscope (PHILIPS CM120, Eindhoven, Netherlands) image of tumour cell-derived exosomes. Scale bar, 50 nm. Tumour cell-derived exosomes were isolated from tumour conditioned medium using an exosomes isolation kit (Invitrogen Carlsbad, CA, USA). (b) Tumour cells and tumour cell-derived exosomes were lysed with RIPA lysis buffer (Millipore, Darmstadt, Germany) containing a protease inhibitor cocktail (Sigma, St Louis, MO, USA). Protein concentration was quantified by protein assay (Bio-rad, Hercules, CA, USA), and analysed the exosomes markers CD61 (Cell Signaling, Danvers, MA, USA), CD9 (Cell Signaling), TSG101 (Abcam, Cambridge, MA, USA), CYC1 (Cell Signaling), Grp94 (Cell Signaling) and CANX (Santa Cruz, Dallas, TX, USA). (c) Exosomes derived from tumour cells labelled with PKH26 Dye (Sigma) were cultured with BM-MSCs isolated from GFP transgenic mouse for 24 h. The uptake of exosomes by BM-MSCs was observed under fluorescent microscope. Scale bar, 200 μm. (d) B16-F0 melanoma cells (1 × 10⁶) were inoculated into the hind legs of C57BL/6 mice intramuscularly alone or with BM-MSCs or TE-MSCs (2 × 10⁵), which were derived by culturing BM-MSCs with B16-F0-derived exosomes for 6 days (exosomes were added daily at a final protein concentration of 5 μg/ml). The fetal bovine serum used in our experiments was depleted of exosomes by 18 h ultracentrifugation. Tumours were excised and weighed on days 6, 9 and 12 post tumour inoculation. All procedures were approved by the Institutional Animal Care and Use Committee of the Institute of Health Sciences, Shanghai Institutes for Biological Sciences of Chinese Academy of Sciences. Data was shown as mean±s.d. (n⩾4). Statistical significance was assessed by nonpaired two-tailed Student’s t-test, with significance set as P<0.05; ns, no significance, *P<0.05, ***P<0.001.