AT-MSCs and MSC-CM can inhibit the proliferation of SKBR3 breast cancer cells. A) MSC-CM-exposed EGFP-SKBR3 cells show significantly increased relative confluence as determined by the kinetic live-cell imaging. Data were pooled from the three independent experiments and expressed as means ± SD. B) Relative proliferation of the SKBR3 cells in serially diluted MSC-CM was determined by the viability luminescence-based assay after 6 days. MSC-CM supplemented culture medium gradually decreased the cell proliferation in comparison to the standard culture conditions. Proliferation was significantly inhibited in each MSC-CM dilution in comparison to standard culture medium (p < 0.05). C) The inhibition of proliferation was determined for the three different AT-MSCs isolates tested as above, *p < 0.05. D) Direct coculture of the EGFP-SKBR3 with AT-MSCs confirmed the inhibition of tumor cell proliferation based on the decrease in relative green fluorescence corresponding to the signal from the viable tumor cells. Relative proliferation was significantly lower in comparison to the proliferation of EGFP-SKBR3 alone when ≥ 1,000 AT-MSCs were admixed to the 10,000 EGFP-SKBR3 cells (p < 0.05). E) Immunoassay confirmed the production of SDF-1α in the AT-MSCs and cocultures of AT-MSCs and EGFP-SKBR3. F) EGFP-SKBR3 cells were cultured in the presence of AT-MSCs CM or AT-MSCs with or without 5 μg/ml AMD3100 - specific inhibitor of SDF1α/CXCR4 signaling. Relative tumor cell viability was significantly lower in the presence of AT-MSCs and the inhibitory effect was abrogated in the presence of the AMD3100. Each experiment was performed at least three times in quadruplicates with similar results and one representative outcome is shown. Data were expressed as means ± SD. *p < 0.05.