Fig. 6: hMSC-derived let-7f has anti-tumor effect in vivo.
A Schematic presentation of the experimental procedure and time line for use of the multicellular tumor spheroid model. 1 × 106 4T1 tumor cells were mixed in a 1:1 ratio with hMSCs transfected with let-7f mimics (hMSC/M), let-7f inhibitor (hMSC/I) or control oligonucleotides (hMSC/C) and cultivated for 2 days in collagen I gels. 2 × 106 4T1 tumor cells were used as a control (4T1 + 4T1). The resulting 3D tumor spheroids were then implanted into the inferior mammary of 16 BALB/c mice (4 mice per group). After 3 weeks, the mice were sacrificed and the tumor spheroids removed by surgery for further analysis. B Phase-contrast microscopy pictures representative of the resulting spheroids. Scale bars 100 µm. C Photographs of the respective tumors after removal from the mice. Scale bars 5 mm. D The results of quantification of the tumor masses determined by weighing are shown. **P < 0.01, n.s. not significant. E 4T1 cells stained with CellTracker CMFDA (green fluorescence) and hMSCs stained with CellTracker CMTPX (red fluorescence) were mixed in a 1:1 ratio. The resulting spheroids were implanted into the inferior mammary of BALB/c mice and after three weeks analyzed by intravital microscopy analysis. Photographs of the respective tumor after removal from the mice. Scale bars 1 mm.
