Figure 1Macrophage-conditioned medium induces MCF10A colony formation in soft agar as compared to control medium. Colonies ≥ 50 μm were counted at 5 weeks. Error bars represent mean ± SEM from 10 independent experiments (n=3 per condition). Macrophage donors are indicated as D1-D16. M1D - M1 differentiated, M1A - M1 activated, M2D - M2 differentiated, M2A - M2 activated macrophages.16-days old MCF10A spheroids grown in matrigel/collagen mix were stimulated for 24h with either macrophage-conditioned or control medium. Representative images of MCF10A spheroids categorized into 4 groups according to the filling of the lumen with cell nuclei (clear, partially filled, almost filled and filled). Spheroids stained for DNA (Hoechst 33342 in blue) and F-actin (Phalloidin in red).16-days old MCF10A spheroids grown in matrigel/collagen mix were stimulated for 24h with either macrophage-conditioned or control medium. Macrophage-conditioned medium induces filling of the spheroid lumen with cell nuclei compared to control. Error bars represent mean ± SEM from 11 independent experiments (n=2 per condition; 50 spheroids each). Macrophage donors are indicated as D1-D16. M1D - M1 differentiated, M1A - M1 activated, M2D - M2 differentiated, M2A - M2 activated macrophages.16-days old MCF10A spheroids grown in matrigel/collagen mix were stimulated for 24h with either macrophage-conditioned or control medium. Representative images of Ki67 positive nuclei of MCF10A cells. Spheroids stained for DNA (Hoechst 33342 in blue), F-actin (Phalloidin in red) and Ki67 (green).16-days old MCF10A spheroids grown in matrigel/collagen mix were stimulated for 24h with either macrophage-conditioned or control medium. Quantitative analysis of Ki67 positive nuclei per spheroid indicates enhanced proliferation of MCF10A cells upon stimulation with M1 macrophage-conditioned media. Error bars represent mean ± SEM from 3 independent experiments (20-30 non-empty spheroids per condition). Macrophage donors are indicated as D1-D16. M1D - M1 differentiated, M1A - M1 activated, M2D - M2 differentiated, M2A - M2 activated macrophages.16-days old MCF10A spheroids grown in matrigel/collagen mix were stimulated for 24h with either macrophage-conditioned or control medium. NSC23766 (Rac1 inhibitor; 50 μM) reduces the filling of the spheroid lumen with cell nuclei upon macrophage-conditioned medium stimulation compared to control. Filling of the spheroid lumen with cell nuclei categorized into 4 groups (clear, partially filled, almost filled and filled). Error bars represent mean ± SEM from 3 independent experiments (n=2 per condition; 50 spheroids each). Partially filled, almost filled and filled MCF10A spheroids were combined together (non-empty spheroids) for statistical analysis. Macrophage donors are indicated as D1-D16. M1D - M1 differentiated, M1A - M1 activated, M2D - M2 differentiated, M2A - M2 activated macrophages.16-days old MCF10A spheroids grown in matrigel/collagen mix were stimulated for 24h with either macrophage-conditioned or control medium. Invasive protrusions of spheroids into matrigel/collagen mix marked with a white arrow.16-days old MCF10A spheroids grown in matrigel/collagen mix were stimulated for 24h with either macrophage-conditioned or control medium. 3D structures of spheroids stained for DNA (Hoechst 33342 in blue), F-actin (Phalloidin in red) and laminin V (green). Laminin V staining indicates the loss of basal membrane continuity at invasive protrusions. Invasive protrusions are marked with a white arrow.16-days old MCF10A spheroids grown in matrigel/collagen mix were stimulated for 24h with either macrophage-conditioned or control medium. Macrophage-conditioned medium induces invasive protrusions in MCF10A spheroids compared to control. Error bars represent mean ± SEM from 11 independent experiments (n=2 per condition; at least 15 spheroids each from at least 2 fields of view). Macrophage donors are indicated as D1-D16. M1D - M1 differentiated, M1A - M1 activated, M2D - M2 differentiated, M2A - M2 activated macrophages.